Ontario 4R Nutrient Management Stewardship Guide

ONTARIO 4R NUTRIENT MANAGEMENT STEWARDSHIP GUIDE APRIL 2016

This manual will assist agriculture stakeholders understand and apply 4R nutrient management planning practices.

Writers Christine Brown, CCA, Ontario Ministry of Agriculture, Food and Rural Affairs Tom Bruulsema, CCA, International Plant Nutrition Institute Dale Cowan, CCA, AGRIS and Wanstead Farmers Cooperatives Susan Fitzgerald, Executive Director, Ontario Certified Crop Advisor Association Ivan O’Halloran, Ridgetown Campus, University of Guelph Dale McComb, CCA, Ontario Ministry of Agriculture, Food and Rural Affairs Keith Reid, Agriculture and Agri-Food Canada Trevor Robak, Ontario Ministry of Agriculture, Food and Rural Affairs Acknowledgements Appreciation is extended to Fertilizer Canada for their support in developing this manual and providing graphics and photographs. The support was provided as part of Fertilizer Canada’s 4R Memorandum of Cooperation with the Ontario Ministry of Agriculture, Food and Rural Affairs, and the Ontario Agri Business Association.

The International Plant Nutrition Institute (IPNI) graciously provided graphics and shared content from their 4R publications for use in this guide.

Cover Photo: Courtesy Credit Valley Conservation Note for Certified Crop Advisors If this resource guide is being used as a study reference for the 4R Nutrient Management Specialty, please note that while this guide provides information relevant to each competency area, it should not be presumed that knowledge of the material in this guide alone is sufficient for the Specialty.

Depending on the background knowledge of the candidate, it may also be necessary to review and be familiar with the materials identified in the reference list as well.

First Edition ©2016 Canadian Certified Crop Advisor Association All rights reserved Copies cannot be made without written permission.

The views expressed in the Ontario 4R Nutrient Management Stewardship Guide are the views of the authors and of the Canadian Certified Crop Advisor Association and do not necessarily reflect those of the governments of Canada and Ontario.

This project was funded in part through Growing Forward 2 (GF2), a federal-provincial-territorial initiative. The Agricultural Adaptation Council assists in the delivery of GF2 in Ontario.

Ontario 4R Nutrient Management Stewardship Guide The Ontario agriculture industry recognizes the importance of environmental stewardship and its role in ensuring the proper use of crop inputs. The 4R concept of nutrient management has been developed and is being implemented world-wide by industry, researchers, government agencies, farmers and their advisors. It is centered on the goal of building a nutrient management plan that puts the right nutrient sources, at the right rate, at the right time, and in the right place; the 4Rs of nutrient management. It also considers the economic, social, and environmental dimensions of nutrient management. Because of these considerations, 4R nutrient management is seen as an essential approach to ensuring the sustainability of agricultural systems. The 4R concept is simple but its implementation is knowledgeintensive and site-specific.

Scientific principles guide the development of 4R practices related to source, rate, time and place.

Farmers and crop advisors make sure the practices they select and apply locally are in accord with these principles. The principles are the same globally, but how they are put into practice locally varies depending on each farm and taking into consideration their level of agronomic expertise and access to technology as well as specific characteristics such as: soil, crop type, climate, weather, economics, and social conditions. The 4R concepts also interact with other plant management practices such as tillage, irrigation, drainage, crop rotation, cultivar selection, plant protection and weed control.

The 4R nutrient stewardship approach is an essential tool in the development of sustainable agricultural systems because its application can have multiple positive impacts on increasing food production in an economically viable way while preserving the environment.

The advantages, at the farm level, of practicing 4R nutrient management are: • increasing crop production and improving profitability; • minimizing nutrient loss and maintaining soil fertility; and, • ensuring sustainable agriculture for generations to come.

The benefits to Ontario agriculture in a broader context include: • Natural capital benefits: better crop performance, improved soil health, reduced environmental impacts, and protection of biodiversity.

• Economic benefits: increase in farmers’ profits and economic improvement in their communities.

• Social benefits: positive public image of environmentally responsible farming practices, improved rural livelihoods, stronger farming communities.

The 4R nutrient stewardship concept involves growers and their crop advisors selecting the right source-rate-time-place combination from practices validated by research and conducted by agronomic scientists. Goals for economic, environmental and social progress are set by, and are reflected in, performance indicators chosen by the stakeholders. The resource guide is intended as a support tool in conveying the principles of 4R within an Ontario context.

For additional copies of this guide, contact: Certified Crop Advisor Association 39 William Street • Elmira, ON N3B 1P3 519-669-3350 • sarah.tfio@bell.net • www.ccaontario.com

TABLE OF

CONTENTS Page Proficiency Area I: Nutrient Management Planning.....................................................................6 Competency Area 1: Roles and Responsibilities of Provincial, Local Public and Private Entities in Nutrient Management Planning....................................6 Competency Area 2: CCA’s Responsibility in Integrating 4Rs with a Nutrient Management Plan..............................................................................13 Competency Area 3: Economics of Nutrient Management Planning/Budget for Operation Changes Due to 4Rs............................................................25 Competency Area 4: Environmental and Social Risk Analysis.................................................29 Proficiency Area II: Nitrogen.....................................................................................................33 Competency Area 1: Determining the Right Source of Nitrogen..............................................35 Competency Area 2: Determining the Right Rate of Nitrogen..................................................41 Competency Area 3: Determining the Right Timing of Nitrogen Application.............................54 Competency Area 4: Determining the Right Placement/Method of Application for Nitrogen.......................................................................................64 Competency Area 5: Environmental Risk Analysis for Nitrogen...............................................71 Proficiency Area III: Phosphorus................................................................................................78 Competency Area 1: Determining the Right Source of Phosphorus...........................................78 Competency Area 2: Determining the Right Rate of Phosphorus..............................................82 Competency Area 3: Determining the Right Timing of Phosphorus Application..........................87 Competency Area 4: Determining the Right Placement/Method of Application for Phosphorus...................................................................................90 Competency Area 5: Environmental Risk Analysis for Phosphorus............................................94

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Table of Contents

TABLE OF

CONTENTS Proficiency Area IV: Potassium, Secondary Macronutrients and Micronutrients...........................100 Competency Area 1: Determining the Right Source of Potassium, Secondary Macronutrients and Micronutrients.......................................................100 Competency Area 2: Determining the Right Rate of Potassium...............................................116 Competency Area 3: Determining the Right Timing of Potassium Application...........................121 Competency Area 4: Determining the Right Placement/Method of Application for Potassium.....................................................................................122 Competency Area 5: Determining the Right Rate, Timing and Placement of Secondary Macronutrients..................................................................129 Competency Area 6: Determining the Right Rate, Timing and Placement of Micronutrients........136 Competency Area 7: Determining the Right Rate, Timing and Placement of Lime for pH Adjustment..................................................................................143 Proficiency Area V: Manure Management.................................................................................149 Competency Area 1: Whole-Herd or Whole-Flock Total Annual Manure and Nutrient Production............................................................................149 Competency Area 2: Adequacy of the Land Base for Applying Manure..................................154 Competency Area 3: Crediting the Nutrients in Manure for Crop Production...........................156 References...............................................................................................................................163

Please note that while this guide provides information relevant to each 4R competency area, depending on the background knowledge of the reader, it may also be necessary to review and be familiar with the materials identified in the list of references as well. The sources listed were consulted in developing this guide.

Permanently vegetated buffer protecting the banks of the Credit River Photo Source: Credit Valley Conservation

Table of Contents

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PROFICIENCY AREA 1

NUTRIENT MANAGEMENT PLANNING Competency Area 1 Roles and Responsibilities of Provincial, Local Public and Private Entities in Nutrient Management Planning Performance Objective 1 Interpret a CCA’s roles and responsibilities in nutrient management planning as described in the following references: a. N utrient Management Act, 2002 and subsequent revisions, http://www.ontario.ca/laws/statute/02n04 CCAs should know what their clients require to be compliant under the Nutrient Management Act, 2002 (NMA). For example, when a farm unit is “phased in” or required to have a nutrient management strategy, nutrient management plan or NASM plan. b. Nutrient Management Regulation and Protocols, http://www.omafra.gov.on.ca/english/environment/laws.htm#5 Regulation 267/03 and the associated protocols set out specific requirements for planning, storage, and land application standards including maximum application rates and setbacks from wells and surface and groundwater. It specifically identifies the activities and people to which the regulation applies and defines the responsibilities and requirements of people impacted by the regulation.

• Built on best management practices.

• Sets a minimum standard across the province (Ontario) for protecting surface and groundwater.

• Regulations address the production, storage and utilization of land applied materials containing nutrients.

• Designed to provide a level playing field across the province.

• Operations are generally “phased-In” dependent upon the requirements based on the number of animals on the farm, the construction of barns or manure storages, and/or the land application of NASM. Nutrient Management Act, e-Laws and other Regulation links: • Nutrient Management Act, 2002 - www.ontario.ca/laws/statute/02n04 • Nutrient Management Act, 2002, Ontario Regulation 267-03: General www.ontario.ca/laws/regulation/030267 • Nutrient Management Act, 2002, Ontario Regulation 300/14: Greenhouse Nutrient Feedwater www.ontario.ca/laws/regulation/140300

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PROFICIENCY AREA I - Nutrient Management Planning

•N utrient Management Act, 2002, Ontario Regulation 106/09: Disposal of Dead Farm Animals www.ontario.ca/laws/regulation/090106 Nutrient Management Protocols • 2012 Nutrient Management Protocol http://www.omafra.gov.on.ca/english/nm/regs/nmpro/nmprotc-12.htm - 2012 Nutrient Management Tables http://www.omafra.gov.on.ca/english/nm/regs/nmpro/nmtabtc-12.htm - 2015 Nutrient Management Tables Proposed Updates http://www.omafra.gov.on.ca/english/nm/regs/nmpro/nmtabtc-15.htm • 2015 Greenhouse Nutrient Feedwater Management Protocol http://www.omafra.gov.on.ca/english/nm/regs/gnfpro/gnfpro-15.htm - 2014 Greenhouse Nutrient Feedwater Management Table http://www.omafra.gov.on.ca/english/nm/regs/gnfpro/gnfmantable.htm NMAN software (AgriSuite) includes the tables referred to in the protocols and flags plans where the actions will not meet the regulations. c. Nutrient Management Best Practices, http://www.omafra.gov.on.ca/english/agops/index.html A Best Management Practice (BMP) is a proven, practical and affordable approach to conserving resources such as air, water and soil. The key characteristics are: • practices used on a farm to reduce the potential of causing an adverse effect; • allows individual assessment of situations or risk and personalized management choices; • culturally accepted and voluntarily practiced; and, • scientifically supported.

The Best Management Practices Series can be ordered via the OMAFRA website http://www.omafra. gov.on.ca/english/environment/bmp/series.htm The available Best Management Practices Books are listed below: • An Introduction to Best Management Practices • A First Look • A Phosphorus Primer • Agroforestry Series Volume 1 - Woodlot Management • Agroforestry Series Volume 2 - Establishing Tree Cover • Application of Municipal Sewage Biosolids to Cropland • Best Management Practices for Phosphorus • Buffer Strips • Controlling Soil Erosion on the Farm • Cropland Drainage • Deadstock Disposal • Farm Forestry and Habitat Management • Fish and Wildlife Habitat Management • Greenhouse Gas Reduction in Livestock Production Systems • Integrated Pest Management • Irrigation Management • Keeping Your Well Water Safe to Drink (An Information Kit to Help You Care for Your Well) Managing Crop Nutrients

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• • • • • • • • • •

Manure Management No-till: Making It Work Nutrient Management Planning (Revised Edition 2006) On-Farm Energy: A Primer Pesticide Storage, Handling, and Application Self-Assessment and Best Management Practices for Water and Fertilizer Use In Greenhouse Vegetable Production (Web Only - PDF) http://www.omafra.gov.on.ca/english/ environment/bmp/greenhouse.pdf Soil Management Streamside Grazing Water Management Water Wells

d. International Plant Nutrition Institute (IPNI) 4R Stewardship, http://www.ipni.net/4r More global in perspective, IPNI initiated the 4R concept through cooperation between the fertilizer industry and the scientific community. The global framework facilitates the development of site and crop specific fertilizer BMPs based on sound science. The principles are universal, but their implementation must be adapted to the local context at different scales. e. 4R Nutrient Stewardship, http://www.nutrientstewardship.com/ Fertilizer is a component of sustainable crop production systems, and the fertilizer industry recognizes the need to efficiently utilize these nutrients. This site provides science-based information for stakeholders to utilize for education, advocacy, and implementation of crop nutrient stewardship. It provides information on fertilizer best management practices that benefit the environment and the producer’s bottom line. The site is a collaborative effort of the fertilizer industry.

The guidelines for the 4R principles are endorsed and supported by the International Plant Nutrition Institute, The Fertilizer Institute, The Canadian Fertilizer Institute, and the International Fertilizer Industry Association. f. Fertilizer Canada Nutrient Stewardship, http://fertilizercanada.ca/nutrient-stewardship/4rs-across-canada/ontario/ Fertilizer Canada (operating name for the Canadian Fertilizer Institute) is an industry association that represents manufacturers, wholesale and retail distributors of nitrogen, phosphate and potash fertilizers.

The Nutrient Stewardship webpage houses Fertilizer Canada’s 4R Nutrient Stewardship programs across Canada where each project shares a common goal of applying the 4Rs to increase production/ profitability for growers while enhancing environmental protection and improving sustainability for the region.

For Ontario, there is a 4R Nutrient Stewardship Guidance Document http://fertilizercanada.ca/wpcontent/uploads/2016/01/Ontario.pdf. As well, Fertilizer Canada and Ontario partners are working on a 4R program to directly engage growers in implementing 4R stewardship practices on farm. This will include a strong role for CCAs employed at the crop input retailer level in working directly with growers.

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PROFICIENCY AREA I - Nutrient Management Planning

g. A griculture and Agri-Food Canada – Nutrient Management Planning, http://www.agr.gc.ca/eng/science-and-innovation/agricultural-practices/soil-and-land/soilnutrients/nutrient-management-planning/?id=1187355760327 The website has general information on nutrient management planning in the broad sense as well as best management practices for soil and nutrients. h. Agriculture and Agri-Food Canada – Agricultural Practices, http://www.agr.gc.ca/eng/science-and-innovation/agricultural-practices/?id=1360876327795 The website has general information on: •A groforestry - Benefits of agroforestry practices, best practices for growing trees and how to plan and establish wind breaks.

• Climate - Information on how changing climate affects agriculture.

• Soil and Land - Soil protection and management.

•W ater - Information on livestock watering, ponds and dugouts, watershed protection, wells and groundwater.

Uniform application of liquid manure to a growing crop.

Courtesy Christine Brown

PROFICIENCY AREA I - Nutrient Management Planning

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Performance Objective 2 Interpret roles and responsibilities of provincial, local public and private entities in nutrient management planning.

Provincial (government) • Provide background information on the Nutrient Management Act (NMA), definitions, regulations and protocols.

• Provide training and resources for people subject to the regulation.

• Provide certification and training for third parties (consultants/applicators).

• Ensure a timely application approval process.

• Provide inspections and enforcement tools to ensure regulation compliance.

• Regular communication with stakeholders to ensure the regulation is having the intended impact.

• Integrate nutrient management principles into source water protection planning as it relates to the Clean Water Act for municipal drinking water supplies.

Certificates and Licences • Agricultural Operation Strategy or Plan Development Certificate (AOSPDC) - This certificate is for third party individuals (consultants) who prepare nutrient management strategies and plans for Agricultural Source Materials (ASM) for agricultural operations phased in under the NMA. • Agricultural Operation Planning Certificate (AOPC) – This certificate is for owners/operators or farm staff members preparing nutrient management strategies and plans solely for their operation.

• Broker Certificate – Required for those acting as a broker for a transaction involving ASM for phased-in operations with NMS, NMP or NASM plan.

• Prescribed Materials Application Business (PMAB) Licence – Required for those engaged in the business of applying materials to agricultural land phased-in with a plan or NASM plan.

• Non-Agricultural Source Material (NASM) Plan Development Certificate – Certificate for individuals who prepare NASM plans as required by the NMA. • Nutrient Application Technician Licence – For third party individuals applying nutrients to agricultural land (phased-in) with a NMP or NASM plan.

Local public (municipal) • When a nutrient management strategy has been completed and approved, issue building permit for new buildings that are phased into nutrient management, and ensure building permit is followed.

• Local Advisory Committees as established under the NMA • Source water local committees • Farm source water protection plan Private (landowner/consultants) • Provide required documentation.

• Certified personnel prepare nutrient management strategies and nutrient management plans.

• Provide required and correct information for documentation required for Nutrient Management Act and/or Clean Water Act. • Certified personnel prepare Non-Agricultural Source Materials (NASM) plans for farms receiving materials.

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PROFICIENCY AREA I - Nutrient Management Planning

• L andowner follows nutrient management regulations and/or Best Management Practices (BMPs) using the 4R principles.

• Ontario Environmental Farm Plan - Includes workshops and voluntary self-assessment of farm practices for every aspect of the farm and Best Management Practices worksheets to help guide improvements.

Performance Objective 3 Discuss national, province-specific, and local-specific policies that relate to nutrient management planning.

National • Canadian Environmental Protection Act, 1999 • Fisheries Act - Under the Fisheries Act, the federal government regulates water pollution and prohibits any discharge of a “deleterious substance” into water frequented by fish, and any works or undertakings that result in the “harmful alteration, disruption or destruction” of fish habitat.

Provincial • MDS (minimum distance separation) for new construction projects. Impacts where a building is sited based on end use (livestock, odour, manure storage) and the distance separation from other residences, wells, sensitive features, lot lines, etc.

• Environmental Protection Act (EPA) – General waste management.

• Ontario Water Resources Act (OWRA) - Protecting surface and groundwater.

• Farming and Food Production Protection Act (FFPPA) - Normal Farm Practices. Helps define normal farm practices including, nutrient management and odour, and has established a process for normal farm practices conflict resolution and dealing with public complaints • Clean Water Act (source water protection) – for municipal water supplies. The Ministry of Environment and Climate Change identified potential threats to municipal water supplies and set provincial standards for safeguarding those water sources.

• Nutrient Management - Greenhouse Nutrient Feedwater Regulations (storage, management, land application) - Requirements for on-farm anaerobic digestion facilities - Disposal and management of dead farm animals - Odour guidelines for Non Agricultural Source Materials (NASM) Local-specific • Source Water Act – Local source water protection committees were established to develop the voluntary farm assessment tool designed to address farm practices outside the defined exclusion zone (100 m well head protection zone or immediate intake point for municipal surface water). Local “Risk Management Plans” were developed by the Ontario Farm Environmental Coalition with the intent that they would meet local standards that would exceed provincial standards.

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Performance Objective 4 Interpret and understand the certification process under the province’s Nutrient Management Act and Regulations.

The table below summarizes the certification requirements for individuals preparing a nutrient management strategy (NMS), nutrient management plan (NMP) or a non-agricultural source material plan (NASM). A farmer may prepare their own NMS or NMP however a NASM Plan Developer certification is required for individuals preparing NASM plans.

Table 1.1. Summary of Preparation Options for NMS, NMP and NASM Plans Options for preparation

Certificate requirement

Requirements

NMS or NMP prepared Agricultural Operation Planning Certificate by farmer

• Nutrient Management Regulations and Protocols course • Introduction to Nutrient Management course or equivalent • Apply for certification

NMS or NMP prepared Agricultural Operation Strategy and Plan by a certified Development Certificate consultant

• Introduction to Nutrient Management • Regulation and Protocols • How to Prepare a Nutrient Management Strategy and Plan (using NMAN) • Using NMAN software, complete two fictitious NMPs or NMSs • Pass an exam • Apply for certification

NASM Plan prepared by a certified consultant

NASM Plan Developer’s Certificate

• NASM Plan Developers Course • Introduction to Nutrient Management course • NMAN software course • Complete required assignments and • Pass an exam • Apply for certification

Performance Objective 5: a. Identify responsible parties and their roles in implementing each component of a Nutrient Management Plan following the Nutrient Management Act. b. Identify the logistics needed to apply the right source of nutrients at the right rate, at the right time, and in the right place. a. Refer to Performance Objective 3 above. b. Refer to Performance Objective 6 below.

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Competency Area 2 CCA’s Responsibility in Integrating 4Rs with a Nutrient Management Plan Performance Objective 6 Differentiate between regulated Nutrient Management Planning and 4R nutrient management planning.

Table 1.2 C omparison of Regulated Nutrient Management Planning to 4R Nutrient Management Planning Regulated Nutrient Management Planning

4R Nutrient Management Planning

• The goal of nutrient management planning is to manage nutrients to optimize beneficial use of nutrients for crop production, to minimize environmental impacts of nutrients and to identify and manage the areas of risk on agricultural operations.

• Regulation addresses production, storage and utilization of materials containing nutrients that can be applied to land.

• Goal of fertilizer BMPs is to match nutrient supply with crop requirements and minimize nutrient losses from fields.

Right Source

• Supply nutrients from livestock or non-agricultural sources with analysis to estimate plant-available nutrients.

• Suit the physical site conditions. Examples include avoiding surface application of nutrient-rich or phosphorus-containing materials to frozen or snow covered soils, or matching application of materials containing high organic nitrogen to crops requiring rapid N release.

• Understand the analysis of the material so that commercial fertilizer equivalents can be deducted and/or additional requirements can be supplemented.

• Be aware of contaminants, trace elements and/or salt content of various organic amendments (NASM materials) and any restrictions on application rate or placement (setbacks) that may accompany these materials.

Matches fertilizer type to crop needs • Placing fertilizer with seed • Looking at nitrogen pathways • Split fertilizer application • Soil sampling to determine needs • Soil pH and nutrient availability

Right Rate

• Calculate plant nutrient demand. Yield is directly related to the quantity of nutrients taken up by the crop until maturity. The selection of a meaningful yield target attainable with optimal crop and nutrient management and its variability within fields and season to season thus provides important guidance on the estimation of total crop nutrient demand.

• Use adequate methods to assess soil nutrient supply. Practices may include soil sampling, plant tissue analysis, response experiments, control plots, etc.

• Assess all available nutrient sources. For most farms, this assessment includes quantity and plant availability of nutrients in manure, compost, biosolids, crop residues, irrigation water, as well as commercial fertilizers.

• Predict fertilizer use efficiency. Some loss is unavoidable, however, site conditions at the time of application should be considered to minimize losses to the environment. Application of organic materials to encourage loss so that a higher application rate can be applied is irresponsible. So, to meet plant demand, that amount must be considered.

Matches amount of fertilizer to crop needs • Placing fertilizer with seed • Looking at nitrogen pathways • Split fertilizer application • Soil sampling to determine needs • Soil pH and nutrient availability

Goal

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Table 1.2 C omparison of Regulated Nutrient Management Planning to 4R Nutrient Management Planning ~ Continued Regulated Nutrient Management Planning

4R Nutrient Management Planning

Right Rate

• Consider soil/crop rotation nutrient balances. If the output of nutrients from a cropping system exceeds inputs, soil fertility declines in the long term. Often, livestock operations with limited land base, apply nutrients in excess of soil/ crop requirements resulting in long-term fertility build-up to levels that increase environmental risk.

• Incorporate rate-specific economics. Consider where manure or other organic amendments are applied at specific points in the crop rotation (at rates that include nutrients for the subsequent crop). Avoid application of phosphorus or nitrogen above crop nutrient removal. For nutrients unlikely to be retained in the soil, the most economic rate of application is where the last unit of nutrient applied is equal in value to the increase in crop yield it generates (law of diminishing returns). For nutrients retained in the soil, their value to future crops should be considered.

Matches amount of fertilizer to crop needs • Placing fertilizer with seed • Looking at nitrogen pathways • Split fertilizer application • Soil sampling to determine needs • Soil pH and nutrient availability

Right Time

• Evaluate logistics of farm and field operations. Timing of nutrient applications should be planned as close to crop needs as possible and at times when the site and soil conditions are suitable. (i.e. incorporation, low risk of compaction, no rain in immediate forecast). Nutrient applications should not delay time-sensitive operations such as planting, in which case more diverse crop rotations that allow application at alternate times during the growing season (i.e. forages or wheat with cover crops) may be required.

• Assess timing of plant uptake. Nutrients should be applied to match the crop nutrient demand which depends on planting date, plant growth characteristics, sensitivity to deficiencies at particular growth stages, etc.

• Assess dynamics of the manure or organic amendment nutrient availability and/ or when risk of loss is high. Be aware of the nitrogen composition for availability.

Mineralization of soil organic matter from previous applications can supply a large quantity of some nutrients but if the crop’s uptake need precedes its release, deficiencies may limit productivity.

• Recognize dynamics of soil nutrient loss. For example, leaching losses tend to be more frequent in the spring and fall. Phosphorus loss can be high with surface applied material during the non-growing season where risk of runoff and/or erosion is high.

• Evaluate logistics of field operations.

Matches nutrients available when crops need them • Placing fertilizer with seed • Looking at nitrogen pathways • Split fertilizer application • Soil sampling to determine needs • Soil pH and nutrient availability

Right Place

• Assess land base, crop rotation, site characteristics, field fertility levels, equipment and labour logistics, etc. to plan which fields will benefit most from application of organic amendments • Where possible, plan to incorporate nutrients as soon after application as possible (i.e., liquid materials with high ammonium-N or materials with odour) •D etermine where sensitive areas require set-back from material application (i.e. water courses, residential areas, municipal wells etc.)

• I n application to no-till fields or fields with living crops, attention to site conditions (risk of runoff, preferential flow through tile drains) must be considered to prevent environmental loss or adverse effect.

• S uit the goals of the tillage system. Subsurface placement techniques that maintain crop residue cover on the soil can help conserve nutrients and water.

•M anage spatial variability. Assess soil differences within and among fields in crop productivity, soil nutrient supply capacity, and vulnerability to nutrient loss.

Keeps nutrients where crops can use them • Placing fertilizer with seed control products • Looking at nitrogen pathways • Split fertilizer application • Soil sampling to determine needs • Soil pH and nutrient availability

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PROFICIENCY AREA I - Nutrient Management Planning

Performance Objective 7 Plan the right source(s), at the right rate(s), at the right time(s), and the right place(s) to fit the client’s cropping system, climate, soils, and farming situation.

Right Source • Supply nutrients in plant-available forms.

The nutrient applied is plant-available, or is in a form that converts timely into a plantavailable form in the soil.

• Suit the physical and chemical soil properties. Examples include avoiding nitrate application to flooded soils, surface applications of urea on high pH soils, etc.

• Recognize interactions among nutrient elements and sources. Examples include the P-zinc interaction, N increasing P availability, fertilizer complementing Spring Application of Dry Fertilizer on Winter Wheat.

Courtesy Christine Brown manure, etc.

• Consider blend compatibility. Certain combinations of fertilizer types attract moisture when mixed, limiting uniformity of application of the blended material. Granule size should be similar to avoid product segregation, etc.

• Understand the benefits and sensitivities of various fertilizer sources to associated elements.

Most nutrients have an accompanying ion that may be beneficial, neutral or detrimental to the crop. For example, the chloride (Cl-) accompanying K in muriate of potash is beneficial to corn but can be detrimental to the quality of tobacco and some fruits. Some sources of P fertilizer may contain plant-available Ca and S, and small amounts of Mg and micronutrients, • Control effects of non-nutritive elements. For example, natural deposits of some phosphate rock contain non-nutritive trace elements. The level of addition of these elements should be kept within acceptable thresholds.

Right Rate • Calculate plant nutrient demand. Yield is directly related to the quantity of nutrients taken up by the crop until maturity. The selection of a meaningful yield target attainable with optimal crop and nutrient management and its variability within fields and season to season thus provides important guidance on the estimation of total crop nutrient demand.

• Use adequate methods to assess soil nutrient supply. Practices may include soil sampling, plant tissue analysis, response experiments, control plots, etc.

• Assess all available nutrient sources. For most farms, this assessment includes quantity and plant availability of nutrients in manure, compost, biosolids, crop residues, atmospheric deposition, irrigation water, as well as commercial fertilizers.

• Predict fertilizer use efficiency. Some loss is unavoidable, so to meet plant demand, that amount must be considered.

• Consider soil resource impacts. If the output of nutrients from a cropping system exceeds inputs, soil fertility declines in the long term.

• Incorporate rate-specific economics. For nutrients unlikely to be retained in the soil, the most economic rate of application is where the last unit of nutrient applied is equal in value to the increase in crop yield it generates (law of diminishing returns). For nutrients retained in the soil, their value to future crops should be considered. Assess probabilities of predicting economically optimum rates and the effect on net returns arising from error in prediction.

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Right Time • Assess timing of plant uptake. Nutrients should be applied to match the crop nutrient demand which depends on planting date, plant growth characteristics, sensitivity to deficiencies at particular growth stages, etc.

• Assess dynamics of soil nutrient supply. Mineralization of soil organic matter supplies a large quantity of some nutrients but if the crop’s uptake need precedes its release, deficiencies may limit productivity.

• Recognize dynamics of soil nutrient loss. For example, leaching losses tend to be more frequent in the spring and fall.

• Evaluate logistics of field operations. For example, multiple applications of nutrients may or may not combine with those of crop protection products. Nutrient applications should not delay time-sensitive operations such as planting.

Right Place • Take into account where crop roots are growing. Nutrients need to be placed where they can be taken up by growing roots when needed.

• Consider soil chemical reactions. Concentrating soil-retained nutrients like P in bands or smaller soil volumes can improve availability.

• Suit the goals of the tillage system. Subsurface placement techniques that maintain crop residue cover on the soil can help conserve nutrients and water.

• Manage spatial variability. Assess soil differences within and among fields in crop productivity, soil nutrient supply capacity, and vulnerability to nutrient loss.

Performance Objective 8 Evaluate the considerations to plan logistics for the equipment, labor, and nutrient materials to develop a 4R nutrient management plan for a given operation.

See Table 1.3 in Performance Objective 16 for the basic steps involved in developing, monitoring and maintaining a 4R nutrient management plan.

When developing a 4R nutrient management plan, consideration has to be given to the feasibility of implementing the plan. Factors include: crops and varieties to be grown, optimum planting dates and corresponding nutrient application dates, inventory of available equipment, and manpower hours required. An assessment must be made regarding the practicality of all field work being handled within the farming operation or the opportunity to utilize custom operators.

Considering the logistics of the operation can help with 4R nutrient management plan. For example, increasing opportunities for nutrient/manure application: • Can manure be applied after planting corn, or after forage harvest or after wheat harvest with cover crops?

• If labour or equipment and/or time is a limiting factor (e.g. forage harvest), can utilizing the services of custom manure application and/or custom fertilizer application be an economic consideration?

• Can application during the growing season save on additional storage requirements?

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PROFICIENCY AREA I - Nutrient Management Planning

If soil fertility levels are already high, and land base for manure is limited, are there opportunities to trade manure with neighbouring cash crop farms – potentially for straw, labour, equipment, cash, etc.

Performance Objective 9 Discuss the advantages of using soil test interpretations based on accredited soil tests for making nutrient recommendations.

The Ontario Ministry of Agriculture, Food and Rural Affairs administers a lab accreditation program to ensure quality control and consistent results for soil tests. The lab accreditation program aims to: • provide a correct analytical result for each soil sample submitted to the accredited labs within reasonable expectations for each analytical procedure; • provide consistent results from any of the accredited labs; • encourage the use of appropriate soil test extractants for which there is a body of fertilizer response calibration data for Ontario soils; • promote the use of accredited labs which perform the standard analyses and perform them correctly; and, • promote the use of the fertilizer recommendations based on Ontario research.

In summary, the advantages of using soil test interpretations based on accredited soil tests are: consistency, reliability, and applicability to your growing area.

Performance Objective 10 Discuss the underlying field research required to calibrate a given soil test extraction method, i.e. to derive nutrient recommendations from the test values.

The choice of an extractant is specific to each region since the most appropriate extractant will depend to a large extent on the soils of that region. The first step in determining an appropriate extractant or soil test method is to collect samples of a wide range of soils from across the region and then to grow plants in each soil. These plants are harvested, weighed and analyzed to find the amount of nutrient taken up by the plants from the different soils. Different extractants are used to remove the nutrients from the soils and the extracts are analyzed. The final step compares the results of the extractions with the amount taken up by the plants which is the measure of the nutrient-supplying capacity of the soil. The extractant chosen for a region is normally the one with the highest correlation to the plant uptake.

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Performance Objective 11 Justify management actions that should be considered if nutrients need to be applied outside the optimum 4R nutrient management plan.

The 4R nutrient management plan will cover nutrient source, rate, timing and placement. Inclement weather, equipment breakdown, and market availability of crop inputs can impact the implementation of the optimum plan.

If a particular nutrient source is not available or becomes less desirable due to pricing, other sources may be considered taking into account the nutrient requirements of the crop, type of application equipment required, crop growth stage, and crop conditions.

The application rate of nutrients should be managed to match crop needs based on current soil test results and crop production plans. The over application of nutrients, higher than needed for crop response, can lead to increases, or buildup, of soil test levels and also directly increase risk of nutrient loss, particularly when the source is surface applied without incorporation.

In the case of manure management on livestock and poultry farms, if nutrient rates are at the maximum, some alternatives include: finding a manure broker who could take the excess nutrient, finding a neighbor (e.g. cash cropper) who might accept the excess nutrient.

Some nutrients are ideally applied in split applications however weather factors may necessitate changing to a single application or utilizing a different method of application. If the timing of nutrients changes significantly so that the crop has progressed to a different growth stage, both the nutrient source and application method/placement may have to be changed.

Refer also to the individual nutrient chapters in this guide for more detailed information on factors to be considered for each nutrient.

Performance Objective 12 Discuss consequences of increasing soil nutrient levels above the crop nutrient response level.

As nutrient levels increase, yields will likewise increase until nutrient levels become excessive and then yields will begin to decline. In most cases, maximum economic yield is also the point where the plant is making the best use of the fertilizer. Using excessive rates reduces profitability for the farmer and directly increases the risk of nutrient loss particularly when the source is surface applied without incorporation. This can lead to an increased environmental risk for surface or groundwater contamination.

As noted above, increasing fertilizer application rates might even result in crop yield loss. For example, too much nitrogen fertilizer results in excess vegetative growth which reduces the reproductive growth which is needed to maintain large yields of seed, grain, or fruit. A thick vegetative canopy promotes disease by slowing drying leading to higher costs for disease control. It can also lead to lodging and associated yield loss.

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Excess nutrients can also affect crop quality especially in horticulture crops. In apples, excess nitrogen can result in soft fruit with poor color. In grapes, it will delay ripening.

Excessive nutrients can interact with the availability of other nutrients potentially causing deficiencies or toxicities. For example, too much potassium can cause bitter pit in apples by interfering with calcium uptake.

For crops grown for animal feed, care must be taken that applied nutrient levels do not negatively affect the nutrient content of the resulting feed. For example, excessive soil K will reduce magnesium uptake in forages, this may be a health concern when livestock consume forages testing low in Mg.

Performance Objective 13 Evaluate a CCA’s professional risks and responsibilities related to nutrient management planning.

Providing agronomic advice related to nutrient management planning carries the same professional ethics requirements and legal responsibilities as other types of business advice. CCAs must avoid and discourage sensational, exaggerated, or unwarranted claims or recommendations that might encourage growers to participate in unsound practices. CCAs should not give a professional opinion or make a recommendation without being as thoroughly informed as possible regarding the products, practices and services being recommended and the individual client’s/customer’s farming operation.

Regardless of the particular service rendered or the capacity in which a CCA functions, advisors should protect the integrity of their work, maintain objectivity and disclose any material conflicts of interest (i.e. recommending products or services from which the CCA or their employer may receive financial gain).

CCAs should also recognize the limitations of their individual knowledge and when consultation with other professionals is appropriate or referral to other professionals necessary.

The best interest of the client/customer is protected by recommending only products and services that are beneficial to the client while taking into account and complying with legislation and regulation.

Public good may also be a key factor in terms of environmental stewardship.

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Performance Objective 14 Discuss the components of a 4R nutrient management plan that should be monitored and tracked over time and the impacts of any changes.

•C ropping records should document by field: crops and varieties planted, planting date, seeding rate, date and rate of nutrient applications, date and rates of herbicide and insecticide applications, harvest date, and yields.

• Detail current management practices, e.g. type of tillage system, application practice and/or equipment, etc.

• Soil and manure test results.

• Soil quality in terms of structure, texture, compaction, erosion, etc. should be noted and corrective action taken if negative trends are seen.

• Livestock records, if applicable, including the type of livestock on farm, number of head broken down by age groups, any significant changes in feeding regime and/or ration.

• Water quality in wells and tiles.

• Any mitigation measures implemented, e.g. buffer strips, windbreaks, water and sediment control basins, etc., Refer also to Table 1.3 in Performance Objective 16.

Performance Objective 15 Analyze various changes in the farm operation that will require updates or adjustments to a 4R nutrient management plan such as: a. cropping system or rotation; b. soil test results; c. livestock housing or animal numbers; d. application rate; e. yields.

Cropping System or Rotation When changing crops during the growing season, nutrient amounts and fertilizer formulation should be adjusted to account for a change in crop. If the nutrients have already been applied, the amount and formulation should be adjusted for the next crop where possible, to account for the nutrient needs and removal for the current crop. However, a change in crop grown won’t have that much impact on a plan over the whole crop rotation.

Soil Test Results A proper soil test will help ensure the application of enough fertilizer to meet the requirements of the crop while taking advantage of the nutrients already present in the soil. It will also help determine lime requirements and can be used to diagnose problem areas, e.g. high or low pH, problematic soil texture, adverse nutrient levels, etc. These results can be useful for guidance in management or remediation decisions.

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Soil test results taken over time illustrate changes in soil properties. This is useful to track remediation efforts or determine if unfavorable trends are occurring. Proper management of nutrients balances the requirements of the crop being grown, the nutrients already available in the soil and the proper timing and placement of nutrient additions for the greatest crop response and the least environmental impact.

Livestock Housing or Animal Numbers Take manure samples annually for three years for new facilities, followed with samples every three to five years, unless animal management practices change. The type and age of livestock, feeding ration, bedding, added liquids and storage system all affect the final nutrient analysis of the manure.

Phosphorus tends to be concentrated in the solids, while potassium levels tend to be higher in the liquid portion, therefore the level of agitation will also affect nutrient levels being applied to a field.

Application Rate Changes in the application rates of nutrients may impact soil test levels and/or nutrient availability for the current and subsequent crop. If the timing of nutrient application is changed, e.g. due to unfavourable weather, adjust nutrients applied to reflect the change in time. For example, if changing from a fall manure application to spring application, adjust commercial N to reflect the higher N availability from the manure. Adjust subsequent applications of nutrients to accommodate the change in timing of the nutrient application and record the change in the nutrient management plan.

Yields Nutrient recommendations should always be based on a soil test. If the previous year’s yields were lower than expected due to weather or other unforeseen factor, the need to calculate carryover or a credit is not necessary. If fertility was not removed, then the soil test values should be higher reflecting the need for lower rates of application going forward. Conversely, higher nutrient removal by the previous crop will be reflected in lower soil test values. A higher yield target may require changes to nutrient recommendations to meet crop goals.

Ontario Agricultural Planning Tools Suite for Nutrient Management Planning.

Courtesy Dale McComb

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Performance Objective 16 Demonstrate knowledge of plan implementation, follow-up, and record keeping components of a 4R nutrient management plan.

Table 1.3 Basic Steps in Developing and Maintaining a 4R Nutrient Management Plan Steps

Description

State your direction for nutrient management planning – helps with decision-making • Evaluate land base needs (expanding, more/less rented acreage etc.)

• Optimize economic yields • Manage input costs 1 • Manage available equipment and/or labour for required Set goals field operations • Protect soil and water resources • Comply with regulations • Use of custom work for all or portions of field work • Consider other stakeholders (neighbours, general public, farm associations etc.)

Key Components

• Establish why you’re doing the plan • Seek advice • Create a vision for what the plan will accomplish

• Identify resources on the farm • Describe site characteristics • Detail current management practices • Farm map that includes all fields, and includes wells, catch basins, open drains, streams, rivers, and other environmentally sensitive areas (source-water municipal wells - groundwater time of travel restrictions) 2 Create a picture in time of what’s currently available • What are the available nutrients on the farm? E.g. manure Take within your operation – if you don’t know what you’ve got, nutrients or off-farm nutrient sources, nitrogen credits inventory you don’t know what you need from legumes, commercial fertilizer already applied at a different point in rotation • Interpreted soil test information for each field (based on information provided from regular testing) • Site characteristics that will/could impact the timing or placement of nutrients, risk of leaching, risk of runoff, etc.

• Crop inventory and realistic yield goals (backed up with historical averages) 3 Input and Apply what you have against what you need to do. analyze data

4 Interpret

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• Use NMAN and MSTOR • Determine the amount and type of nutrient sources available for use at an operation • Use soil test information and intended crop types and yields to determine the amount of nutrients needed • Determine land base requirements • Conduct risk assessment

Based on your data analysis, develop options – to manage • List possible management practices risk, decrease input costs, and handle all nutrients • Identify changes to structures and facilities, equipment generated.

• Remember the systems approach

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Table 1.3 Basic Steps in Developing and Maintaining a 4R Nutrient Management Plan ~ Continued Steps

Description

5 Make Select options to meet your goals decisions 6 Act

7 Keep records

“Walk the talk” to meet your goals

Document what actually takes place – develop your own information for future planning, while showing accountability for your actions

Key Components • Consider personal and business goals • Use available resources • Set proper application rates • Honour separation distances • Make an operational plan • Complete day-to-day activities • Account for the impact of outside forces, e.g., weather, markets For each field, for each farm, maintain: • application records; • livestock records; • cropping records; • monitoring records Records should include: • nutrients applied and application method (equipment, depth); and • Date applied and soil and weather characteristics, crop growth stage, etc.

• yield and quality

8 Monitor

Observe the impact of what you do to determine: • Is production on track?

• Is ground and surface water protected?

• Are nutrients cycling properly?

Monitor: • Nutrient levels in soil and manure as it relates to crop performance • Water quality in wells and tiles.

• Livestock performance • Nuisance impacts • Use performance indicators that include soil fertility levels, nutrient use efficiencies, crop balances, yield, economic yield, change in 4-R principles (such as how many acres had all fertilizer banded or immediately incorporated and how does that compare to base-line year)

9 Adjust

Fine-tune your plan, and upgrade technology where appropriate.

• Use information from record keeping and monitoring • Modify plan by repeating Steps 3 to 8

10 Plan Develop a contingency plan. Consider/document the for the “what would I do if….?” unexpected

• Identify resources • Communicate to others involved • Document actions.

Chart adapted from Best Management Practices, Nutrient Management Planning, 2006, p. 31

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Performance Objective 17 Discuss the record keeping responsibilities and the follow-up process with the operator/client and any or all parties involved with components of the plan.

A 4R nutrient management plan is considered a living document that is revised and refined as circumstances change and as more information and knowledge is acquired. Table 1.3 above outlines the various steps involved in developing a 4R nutrient management plan. Ideally, the client would enlist the support of their agronomic advisor during the first stage to assist with detailing current crop management practices, e.g. type of tillage system, application equipment, etc. and setting targets for soil health, water management, crop yields, etc. Advisors may be involved in soil and manure sampling and providing interpretation of the results.

Typically, a crop plan would be developed in the fall or early winter prior to the growing season. The plan should be reviewed once the spring planting season approaches or gets underway and may have to be adjusted due to weather, market fluctuations, product availability, or other factors. Further adjustments in the implementation of the plan may be required and advisors should periodically touch base with their grower customers over the course of the growing season. Any revisions to the plan should be recorded.

After harvest, the year’s results should be reviewed and analyzed prior to developing a plan and setting targets for the subsequent year. When reviewing or making changes to the plan, take into account: • crop yields and response; • soil test results that may show nutrient levels changing over time; • manure sample analysis that may vary; • new technology that may influence application rate or timing; • market fluctuations that may impact the livestock raised, crops grown, end use of products generated, acres of various crops, rotational mix, etc.; • greater understanding of soils and water quality principles; • purchase or rental of additional land base or, conversely, the divesting of land; • personal or personnel changes that may affect the grower’s long-term goals, labour availability, etc.; and, • changes in the community (e.g. urban growth closer to the farm), bylaw changes and new regulations that may affect farming practices.

Performance Objective 18 Discuss the advantages of maintaining consistent field map boundaries and field numbering systems with government agencies, the client, and the consultant.

Maintaining consistent field boundaries and numbering ensures that results can be compared year over year, e.g. application rates and products applied, yields, soil test trends, evaluation of crop varieties and practices, etc. It also provides a common reference for growers, their employees, service providers, and government agencies. This could avoid the negative consequences of a product or practice being applied to the wrong field, e.g. glyphosate being applied to a non-tolerant variety. If the crop is grown for human consumption or a specialty market, individual field identification and tracking of operations on/in that field may be a requirement for a traceability program.

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Competency Area 3 Economics of Nutrient Management Planning/Budget for Operation Changes Due to 4Rs Performance Objective 19 Construct an enterprise budget for each crop production system1.

Choosing what crops or livestock to produce is an essential decision of any farm business. One critical factor in making that decision is the cost of producing the “enterprises” being considered. This is known as enterprise budgeting or cost of production budgeting. Enterprises are a single crop or livestock commodity that produces a marketable product. Cost of Production (COP) budgeting consists of estimating the costs associated with an enterprise and the expected revenue.

While the format of COP budgets can vary they typically include the following sections.

• Revenue: the gross revenue from crop or livestock sales before any expenses have been deducted.

• Direct Variable Costs: expenses for the production of a specific commodity. These change depending on the level of production (e.g., seed, fertilizer, pesticides and feed).

• Indirect Variable Costs: expenses used in producing all commodities on the farm (e.g., fuel, labour and utilities). These also change depending on the level of production.

• Fixed Costs: expenses that remain the same regardless of the level of production (e.g., property taxes, fire insurance and depreciation).

• Net Profit (loss): revenue minus all variable and fixed costs.

If possible, review the cost of production for each individual enterprise for the past three to five years.

This shows how much each is contributing to the whole farm financial picture, illustrating which enterprise is making money and which is not.

Pricing targets for inputs and outputs can be set at different cost breakeven levels. Know your breakeven points. This information allows you to take advantage of buying or selling opportunities when they arise. Use the following formulas to determine breakeven points.

Breakeven price to cover variable costs Total variable costs ÷ Expected yield = $ / unit produced This is the minimum price needed to cover variable costs.

Breakeven price to cover total costs Total costs ÷ Expected yield = $ / unit produced This is the minimum price needed to cover all costs.

Breakeven yield Total costs ÷ Expected price = Unit produced This is the minimum yield needed to cover all costs.

The difficulty many farmers have in COP budgeting is allocating whole farm costs to a specific enterprise. And the more enterprises there are, the more difficult the allocation process.

1. Answer adapted from Guide to Cost of Production Budgeting, Ontario Ministry of Agriculture, Food and Rural Affairs, Factsheet 08-055, 2008.

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Use the three main approaches to estimating enterprise costs: using on farm records, market value information and formula based. A formula-based approach is particularly useful for estimating capital costs associated with farm machinery and buildings. This method takes fuel use and repair rates, replacement costs and years of expected life to insert into formulas that calculate annual variable and fixed costs.

OMAFRA has budgeting tools available for a wide variety of farm enterprises on their website at http://omafra.gov.on.ca/english/busdev/bear2000/Budgets/budgettools.htm See OMAFRA Factsheets Budgeting Farm Machinery Costs, Order Number 01-075 and Lease Agreements for Farm Buildings, Order Number 03-095, for detailed information and tables to calculate machinery and building costs using the formula-based approach.

The American Agricultural Economics Association (AAEA) has guidelines for COP budgeting available in their publication Commodity Cost and Returns Estimation Handbook. This handbook is available at the United States Department of Agriculture’s Natural Resources Conservation Service website at: http://www.nrcs.usda.gov/wps/portal/nrcs/detail/national/technical/econ/ references/?cid=nrcs143_009751

Performance Objective 20 Evaluate changes in benefits, costs and risks of implementing 4R practices including: a. changing fertilizer application methods; b. changing forms of nutrients; c. freight (logistics of handling fertilizer products); d. use of stabilizers and additives; e. risk of timing changes; f. yield increases; g. alternate cropping systems; h. crop insurance (regulations and premiums).

Changing Fertilizer Application Methods • Changing application method can help to match timing of application to the timing of growth stages.

• Different application methods may be better adapted to the overall crop management system, and the efficiency of use of labor and equipment resources.

Changing Forms of Nutrients • The risk of nutrient loss can be significantly reduced, or increased, depending upon which forms are used, and depending upon soil types and weather conditions. Match the form used with the soil type and the expected weather.

• There may be a large differential in the costs when switching from one form to another.

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• T aking a whole farm approach to nutrient management, e.g. accounting for all nutrients available in the soil, manure, etc., allows recycling of nutrients over the entire land base, supplying crops with commercial nutrients only when and where required.

Freight (logistics of handling fertilizer products) • Hauling distance, storage needed, and equipment available all must be included in the decision of which products and forms are selected.

Use of Stabilizers and Additives • Stabilizers and additives can be used to reduce risk and costs of losses of N. • They may allow reduced application rates.

Risk of Timing Changes • Shifting from fall-applied N increases the risk that unfavorable spring weather will delay or prevent spring application.

• Shifting to split or multiple applications increase total application costs and labor expenses.

Yield Increases • Crop yields are important because they help determine fertilizer recommendations for a given crop.

• Yield also helps estimate the nutrients removed from the field. In nutrient management planning, when soil fertility levels are high, application rates are determined by matching rates with nutrient removed by the crop. Higher yields may reflect greater nutrient removal from the soil and thus a higher application rate for the subsequent crop.

Alternate Cropping Systems • Alternate cropping systems that include a more diverse crop rotation can result in additional opportunities for 4R practices and can spread risk/benefits over more crops. Alternate tillage systems (e.g. moving from conventional to no-till) can improve soil characteristics and reduce erosion, but requires a transition period.

• A change in cropping systems may involve the purchase or lease of different equipment and/ or technology or custom application services.

• There may also be additional labour requirements however, the reverse could also be true where there is a labour saving component.

Crop Insurance (regulations and premiums) Crop insurance reduces the financial risk of perils. 4R stewardship and other good management practices will help reduce the impact of crop failures or other insurable events. For example: • Severe rain events will result in less nutrient runoff if fertilizer is incorporated below the soil surface.

• Yield loss due to moisture stress (drought) will be less severe in soils with higher organic matter and water holding capacity.

• Adequate soil fertility and crop management can reduce the impact of winter kill in alfalfa forage crops and winter wheat.

• Water management (including tile drainage, grassed waterways, WASCoBs – water and sediment control basins, etc.) can reduce the amount of time that soils are saturated and water ponds on fields which can reduce crop loss and nutrient loss.

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Performance Objective 21 Evaluate the incremental expected changes in revenue from adopting the 4R practices.

Basically, developing and implementing a 4R nutrient management plan should lead to greater efficiency in terms of nutrient use. Conducting soil tests and analyzing manure samples may result in growers finding that there are many nutrients present but unaccounted for in their operation’s manure and soil. By maximizing the efficiency of use of all sources of nutrients within a farming operation, the grower may be able to reduce fertilizer or fuel costs. Sampling and record keeping may also lead to more efficient use of nutrient sources in terms of timing and method of application. Matching applied nutrients to crop needs and goals could increase yields and/or crop quality leading to increased revenues.

Performance Objective 22 Estimate the costs for nutrient management plans including: plan preparation, record keeping, soil tests, manure tests, and labour.

Many 4R practices do not significantly increase production costs. They mostly involve shifting timing or placement. Some changes in inputs require increased costs, but, if carefully selected, they should also increase yields and thus increase income. There are laboratory costs associated with having soil and manure samples analyzed, however they are easily offset by savings in commercial fertilizer or by ensuring adequate crop nutrition.

Performance Objective 23 Estimate the financial risk or exposure of not following a 4R nutrient management plan.

Growers may apply more nutrients than required which would increase expenses in terms of fertilizer purchased and potentially higher fuel and labour costs if unnecessary applications occurred. This could also negatively impact crop yields and crop quality.

Excess application of nutrients can also lead to the degradation of surface and groundwater through nutrient loss.

If surface or groundwater is negatively impacted as a result of direct action taken by the farming operation, there is the potential for the operation to face legal action. Likewise, if manure is handled in contravention of the requirements of the Nutrient Management Act, the farm operator or manure applicator could face charges and fines.

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Performance Objective 24 Evaluate the potential financial impact (costs and revenues) to an operation of the short-term and the long-term changes required by a 4R nutrient management plan.

4R nutrient management planning helps to: • optimize use of on-farm nutrients; • prevent excessive nutrient build-up; • reduce fertilizer costs; • maintain soil health for successful crop production; and, • reduce environmental risks.

Managing nutrients properly offers both economic and environmental benefits to producers and the rest of society. Efficient use of nutrients from commercial fertilizers, manure or other sources reduces input costs for crop production and minimizes the risk of nutrient loss to ground and surface water.

With rising fertilizer and fuel prices, as well as concerns for environmental stewardship, sound nutrient management is increasingly important for the sustainability of crop and livestock operations.

Competency Area 4 Environmental and Social Risk Analysis Performance Objective 25 Justify why nutrient management is important to the environment and public health.

Agriculture is one of the sources of nitrogen and phosphorus pollution of water in rural areas. Crop nutrients leaving farmland can pollute water. Concentrations of these nutrients in water above tolerable limits can be harmful to humans, livestock and wildlife.

In unpolluted fresh waters, aquatic plant growth including algae is limited by the low level of phosphorus. Phosphates either dissolved or bound to soil particles, can run off land to surface waters such as drainage ditches, streams and rivers. In Ontario, algal growth has periodically made the water in some lakes and rivers unsuitable for drinking or swimming. It has also lead to the death of fish and other aquatic animals from the lack of oxygen in the water.

Nitrate and ammonium are the two forms of nitrogen considered to have an impact on water quality.

Nitrate-nitrogen can leach into groundwater. Young mammals, including people, are susceptible to health effects of high-nitrate drinking water. Consuming water with high nitrate concentrations can cause severe illness or reduce livestock performance. Nitrogen in the ammonia form is very toxic to fish. Contamination of surface water with materials containing large amounts of ammonia can kill large numbers of fish.

Greenhouse gas (GHG) emissions can also be increased with fertilizer and manure use. Nitrous oxide (N20) is almost 300 times more damaging than carbon dioxide C02 and is at highest risk for loss when nitrate levels are high and soils are cool and saturated. Applying nutrients as close as possible to crop needs at the rate required by a crop is the best 4R strategy for reducing GHG emissions

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Performance Objective 26 Discuss why environmental risk analysis is an important component of nutrient management planning.

In the recent past, greater societal awareness regarding water quality and a better understanding of how nutrients cycle though the environment have put the spotlight on all on-farm nutrients. Nutrient management planning helps match the nutrient requirement of the crop with the nutrients available from the soil and those supplied to the crop through application materials containing nutrients such as fertilizer and livestock manure.

Reducing the risk of contamination from a property takes careful planning. A first step in planning is determining what site specific characteristics are present and what risk they pose. The potential for groundwater contamination once a contaminant enters the soil varies from farm to farm and depends on many factors. An environmental risk assessment enables a farmer to address the specific risks that exist on their farmstead that are presented by the storage, handling and application of nutrients.

Injecting Liquid Manure. Courtesy Christine Brown

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Performance Objective 27 Discuss the importance of social and interpersonal concerns in nutrient management planning.

The nutrient management planning process addresses the storage, handling and application of farm nutrients such as manure and fertilizer in a way that is demonstrable and shows due diligence. The aim is to protect rural soil and water, and give farm operators clear instruction on what they need to do to manage nutrients responsibly and meet legislative requirements.

Farmers and their non-farming neighbours have a vested interest in local soil and water quality.

Both want their community to thrive economically. Both prefer a rural way of life. And like people everywhere, they value harmonious relations with their neighbours.

Nevertheless, conflicts do arise. These days many farms need to expand, specialize and adopt new technologies if they are to succeed. Increasingly they are surrounded by relative newcomers who have migrated from urban areas in search of a pastoral lifestyle in the countryside. These and other concurrent trends seem tailor-made to generate misunderstandings.

Farmers should be proactive in establishing communication channels with their neighbours. The best approach is an informal one that brings farmers, neighbours and the greater community together to talk, listen and build mutual respect and trust - long before conflicts take on a life of their own.

Making demonstrable efforts and using recognized practices to protect soil, water and air quality on cropland, along water bodies, and in and around farm buildings is a farmer’s best defence.

While adopting best management practices is important, they do little to pacify neighbours who do not understand or appreciate the efforts and investment you are making in environmental quality or agriculture’s contribution to the economy in general. Simple one-on-one conversations can do much to prevent problems.

It is important to reinforce these conversations with comprehensive planning. These planning efforts demonstrate proactive environmental stewardship and reflect well on the farmer and the agriculture sector. Producing high quality products in an environmentally responsible manner generates consumer confidence.

For example, odour concerns: • Farming operations can generate odours. Odour complaints form the majority of complaints directed to farmers.

• Farmers who have conflict-avoidance strategies receive fewer complaints.

• Developing good communication within the rural community can reduce the number and magnitude of complaints

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Performance Objective 28 Discuss how regulatory requirements may supersede the results of a risk assessment.

In Ontario, the nutrient management regulation (O. Reg. 267/03) sets a base level of environmental protection which farmers must maintain. Many of the regulations are based on historic best management practices that have been generally accepted and voluntarily adopted by livestock producers.

Sometimes these regulatory standards may be more protective than a simple risk assessment might indicate. For example, a farmer may be accustomed to spreading the manure generated by their operation in November and in April. A risk assessment may indicate that they require only 180 days (six months) of storage capacity for the manure generated at this farm. In Ontario, most farms that construct new or expand existing livestock housing or manure storage must have the capacity to store all of the manure generated by the operation for 240 days.

If there is a conflict between the result of a risk assessment and a regulatory requirement, the producer must follow the regulatory requirement.

Performance Objective 29 Interpret how to use soil test results in environmental risk analysis.

A fundamental part of any nutrient management plan is determining how much nutrient is already present in the soil. Only then can a plan be developed to properly manage the nutrients that have been generated on farm as well as nutrients that are being imported onto the property as biosolids or commercial fertilizer.

When nutrients are applied in excess of crop utilization, then over time, nutrient levels will gradually build up in the soil, or move out of the root zone.

Soil test results show the level of nutrient in the soil. As part of a risk assessment, consider: • Use soil test levels to target nutrient application where that nutrient can provide the most benefit. • Low testing field require more nutrients. Higher application rates may present risk of offsite movement of material. Adopt management practices to keep the material in place. • High testing fields may not require any additional nutrient. If nutrients are to be applied to a field where the nutrient level is already high, consider a different nutrient source, a lower rate and/or adopt management practices that ensure that the nutrients do not cause environmental harm.

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PROFICIENCY AREA II

NITROGEN

Introduction to the Nitrogen Cycle A basic understanding of the N cycle is required to appreciate the impact N fertilizer management decisions and environmental conditions have on the fate of that applied N. The N cycle describes the forms of N found in, added to and lost from the soil, and the transformations that these N forms undergo. Many of the transformations are carried out by soil organisms or plants, and therefore these changes are affected by environmental conditions such as soil temperature and moisture content.

Source: International Plant Nutrition Institute

The amount of organic N in the soil is quite large. Soil organic matter typically has a C:N ration of 10:1 to 12:1. In just the top 15 cm (6�) of soil, there is approximately 1,000 kg ha-1 of organic N for every 1% of soil organic matter.

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Soil N exists primarily in three forms or pools of N: organic N, and two mineral forms - ammonium (NH4+) and nitrate (NO3-). The mineral N forms are the ones absorbed by plants. By far the soil organic N pool is the largest, representing over 90% of the N in the soil. Organic N in the soil arises from biological fixation of N by rhizobia in legume plants or by free-living soil organisms, the return of plant residues to the soil, the addition of organic amendments to soils such as animal manure or nonagricultural source materials (NASMs), and through the immobilization of mineral N in the soil by soil microorganisms.

When microorganisms consume (decompose) organic matter, they can either utilize the N in that organic matter for their own needs or, if N is in excess of their requirements, release the N into the soil as NH4+. This process is referred to as mineralization as the N is converted from an organic form to a mineral form. The NH4+ can meet several fates: it is soluble and thus remains in soil solution and can be subjected to leaching but since it is a cation it can be held on the soil cation exchange capacity (CEC) so leaching is usually only a problem in soils that leach quickly and have a low CEC (e.g. sandy soils); it can be fixed inside certain clay minerals (known as NH4+ fixation) which greatly diminishes its plant availability; it can be taken up (immobilized) by other soil organisms or plants; at higher soil pH values more of the NH4+ in solution is found as ammonia (NH3) which can volatilize into the atmosphere from the soil; and certain soil organisms can convert the NH4+ to nitrite (NO2-) and then NO3- through a process called nitrification. Nitrite is very toxic, and is not usually found in soils due to the fact that the formation of NO3- is considerably faster than the formation of NO2-. The conversion of NH4+ to NO3- is called nitrification and is fairly rapid in moist, warm soils.

Nitrate is very soluble and since it is an anion (negatively charged) it is not held by soil particles and therefore prone to leaching. Like NH4+, NO3- can be immobilized by plants and soil microorganisms where it eventually becomes organic N. In poorly drained or anaerobic soils, groups of soil microorganisms use NO3- anion as an oxidizer converting it to various forms of N oxides and N gas.

Complete denitrification to N gas (N2) is not an environmental concern as approximately 78% of the atmosphere is N2 gas. Incomplete denitrification, however, can result in the loss of a potent greenhouse gas, nitrous oxide (N2O), from the soil.

Other additions of N to the soil typically occur as the three forms found in the soil. Organic sources of N are urea, animal manures and non-agricultural source material (NASMs). Ammonium is added to soils in animal manures, some NASMs and as commercial fertilizers. Nitrate is not found in any significant quantities in animal manures but may be found in some NASMs. Nitrate is also added naturally to soils through lightning and rainfall.

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Competency Area 1 Determining the Right Source of Nitrogen Performance Objective 1 Discuss the most common sources of nitrogen used in Ontario.

Urea (46-0-0) • CO(NH2)2 • white solid • produced synthetically from ammonia and carbon dioxide under conditions of high pressure and temperature • most commonly used fertilizer N source worldwide • may contain small amounts (0.5% - 1.5%) of biuret, about 0.3% conditioning agent (formaldehyde or methylene di-urea) and less than 0.5% moisture • grades for foliar application should contain less biuret Urea reacts with water (hydrolyzes) to form ammonium (NH4+) and bicarbonate (HCO3-) in the soil.

The urease enzyme (present in soils, bacteria and crop residues) speeds the process. Surface-applied urea is subject to losses of ammonia through ammonia volatilization. Losses increase with higher soil pH (which can also be increased due to urea hydrolysis), more crop residues and with higher temperatures.

Ammonium nitrate (34-0-0) • NH4NO3 • white solid • produced by combining ammonia with nitric acid • may contain about 1% conditioning agent and 0.5% moisture • more expensive per unit of N than urea • no longer produced in Canada • regulations apply to its transport (Transport of Dangerous Goods Class 5.1) • needs to be kept away from oils and other flammable materials as it can form an explosive mixture • more hygroscopic than urea and may deteriorate in storage during hot weather as crystal phase changes result in a breakdown of the prills When applied to the soil, ammonium nitrate dissolves in the soil water and separates into ammonium and nitrate, both of which can be absorbed by plants. It is slightly more quickly available to plants at low temperatures than urea but, under normal growing conditions, there is no practical difference.

Calcium ammonium nitrate (27-0-0) • uniform mixture of 80% ammonium nitrate and either calcitic or dolomitic limestone • grey-white solid • limestone reduces explosion hazard When applied at equal weights of N, calcium ammonium nitrate is similar to ammonium nitrate. Soil microorganisms are primarily responsible for the nitrification (conversion of ammonium to nitrate) of ammonium in soils which creates acidity. The lime included in the granules balances part of the acidity released during nitrification so that it does not acidify the soil as quickly as ammonium nitrate does.

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Urea-ammonium nitrate solution (UAN) (28-0-0 to 32-0-0) • produced by dissolving urea and ammonium nitrate (50:50) in water • colourless liquid • 28-0-0 can salt out (precipitate out of solution) if the temperature drops below -18°C (0°F) • a more concentrated solution (32-0-0) is available but it is not often used in Ontario because of the salting out factor at higher temperatures (~0°C or 32°F) • similar to urea, it is subject to loss through ammonia volatilization if UAN is applied to the soil surface • herbicides and other pesticides are commonly added to UAN for broadcast application on the soil • lends itself to sidedress applications Avoid applying UAN onto crop foliage as severe burning will result. UAN is the most commonly used liquid fertilizer in Ontario.

Anhydrous ammonia (82-0-0) • NH3 • colourless, pungent gas at atmospheric pressure • manufactured by reacting natural gas with atmospheric N under high pressures and temperatures • handled as a pressurized liquid • it is used as the base for all manufactured N fertilizers • similar to urea and ammonium nitrate in acidifying effect (1.8 lb CaCO3 to neutralize acidity generated per lb of N supplied) Anhydrous ammonia is applied by injecting it into the soil where it vapourizes and dissolves in the soil moisture. To reduce vapour losses to the air, the anhydrous band must be placed deep enough in the soil that the injection slot closes over and forms a good seal.

There is some concern that anhydrous ammonia is harmful to soil life. Within the injection band, high soil pH and hygroscopic conditions are severe enough to kill earthworms and other soil fauna and microflora but this zone is relatively small and dissipates quickly. The population of soil organisms quickly recovers and is actually increased by the addition of N to the soil ecosystem.

Ammonium sulphate (21-0-0-24) • (NH4)SO4 • white to brown solid, industrial by-product obtained by neutralizing ammonia from coke ovens with recycled sulphuric acid or from nylon manufacturing • may contain about 0.5% moisture and minute amounts of nutrients such as K, calcium, copper, iron, manganese and zinc • generally more expensive per unit of N than urea Ammonium sulphate breaks down to ammonium and sulphate when dissolved in the soil water. It is useful for surface broadcast applications as there is less risk of ammonia volatilization. Depending on the source, its form is granular or coarse powder.

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Calcium nitrate (15-0-0) • Ca(NO3)2 • white solid • expensive source of N • used only where both calcium and N are required and soil acidification is undesirable • contains N in nitrate form and water soluble calcium • highly hygroscopic and may liquefy completely when exposed to air with a relative humidity above 47% The highly soluble nitrate-N and calcium are immediately available to the plant.

Potassium nitrate (12-0-44) • KNO3 • white solid • extracted from dry brine lakes (e.g. Dead Sea) or manufactured by reacting potassium chloride and nitric acid • expensive source of N and K • used mainly for horticultural crops, tobacco and hydroponics The above content was adapted from the Soil Fertility Handbook, OMAFRA Publication 611, p. 149-153.

Performance Objective 2 Determine the right source of nitrogen based on: a. crop type and cropping system; b. climate (temperature, precipitation, leaching, and runoff patterns); c. soil texture and the effect of surface soil pH; d. environmental concerns in the local area (surface and groundwater); e. crop stage.

Identification of the most appropriate sources of N for a given situation is generally governed by the method (e.g. fertilizer placement), timing of fertilizer application with respect to seasonal environmental conditions and crop utilization of the applied N and whether the N fertilizer is blended with other fertilizer materials or other nutrients are needed. Generally the most commonly used N fertilizers in field crop production such as urea, UAN, ammonium nitrate, calcium ammonium nitrate and anhydrous ammonia are less expensive than materials such as ammonium sulphate, calcium nitrate and potassium nitrate.

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Crop Type and Cropping System Urea can be bulk-spread, either alone or blended with most other fertilizers. It is recommended that the spreading width not exceed 50 feet when combined with other fertilizer materials. Urea and fertilizers containing urea can be blended quite readily with monoammonium phosphate (11-52-0) or diammonium phosphate (18-46-0). However, urea often has a lower density than other fertilizers with which it is blended. This lack of “weight” produces a shorter “distance-of-throw” when the fertilizer is applied with spinner-type equipment. In extreme cases, this will result in uneven crop growth and “wavy” or “streaky” fields. Reduced rates of urea (maximum 10 kg ha-1) can be placed with the seed of spring oat and barley although it is generally recommended not to apply urea with the seed of crops such as corn, winter wheat, triticale, barley, canola, etc. Liquid fertilizers containing half as much N as P2O5 often contain urea and thus seed applications should be avoided in most instances.

Banding of urea in corn also requires a lower application rate (maximum 40 kg N ha-1) compared to other N sources (maximum 55 kg N ha-1). Using urea in the band also reduces the amount of potassium that can be applied with the seed or in a band near the seed. If using urea, the fertilizer bands can be moved farther from the seed row to avoid toxicity although this may reduce the benefit from other banded nutrients. Urea should not be blended with superphosphates unless applied shortly after mixing. Urea will react with superphosphates, releasing water molecules and resulting in a damp, sticky material which is difficult to store and apply. Similarly, mixing urea with potash (KCl) can result in caking if the material is stored for a long period of time.

Fluid fertilizers can be blended to precisely meet the specific needs of a crop. Solutions of UAN are very versatile and widely used as a source of plant nutrition. Due to its chemical properties, UAN is compatible with many other nutrients and agricultural chemicals and is frequently mixed with solutions containing P, K and other plant nutrients. This may reduce the number of passes required for the crop.

Nitrogen Fertilizer in Storage Courtesy Fertilizer Canada

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Ammonium sulphate is used primarily where there is a need for supplemental N and S to meet the nutritional needs of the crop. Since it only contains 21% N, there are other fertilizer sources that are more concentrated and economical to handle and transport. However, it provides an excellent source of S. Because of the amount of ammonia and salt index, ammonium sulphate fertilizer application in the seed row can lead to either ammonium or salt toxicity, especially if applied with other fertilizer materials.

Ammonium nitrate is a popular fertilizer since it provides half of the N in the nitrate form and half in the ammonium form. The nitrate form moves readily with soil water to the roots where it is immediately available for plant uptake. The ammonium fraction is held on the soil cation exchange capacity (CEC), taken up by roots or undergoes nitrification to nitrate by soil microorganisms. Many vegetable growers prefer an immediately available N source for plant nutrition and use ammonium nitrate. It is also popular for pasture and forages since it is less susceptible to ammonia volatilization losses than urea-based fertilizers when left on the soil surface. Ammonium nitrate is commonly mixed with other fertilizers however the mixtures cannot be stored for long periods as they will absorb moisture from the air and cake. Mixtures with urea result in the formation of a liquid or slurry. There are also concerns for the detonatability (mixtures with sulphates) or combustion (mixture with elemental sulphur) of certain blends. The very high solubility of ammonium nitrate makes it well suited for making solutions for fertigation or foliar sprays.

Anhydrous ammonia is one of the more dangerous chemicals handled on the farm and must be placed well into the soil and properly covered or the NH3 will volatilize from the soil. Pre-plant and sidedress applications of anhydrous ammonia for corn production are possible although care must be taken to ensure the point of injection is far enough from the seed row or developing plant to avoid injury and ammonia toxicity. This obviously impacts the crop type or cropping system where anhydrous ammonia can be used.

Given the relative ease at which N can be lost from the soil, it is preferable to apply N as close to the period of crop uptake as possible. Fall application of N on winter cereals should be limited and the majority of N should be applied the following spring. Application of UAN through streamer nozzles causes little to no leaf burn, however considerable leaf burn and yield reductions can occur if UAN is applied to an emerged crop using flood jet or tee-jet nozzles, especially when combined with contact herbicides. Nitrogen for spring cereal can be either soil applied and incorporated prior to plant, or with a top-dressing application especially when some of the fertilizer N has been applied as a starter at seeding.

Climate (temperature, precipitation, leaching, and runoff patterns) Temperature affects processes within the N cycle through its impact on chemical reactions and microbial activity. In general, when soils are not frozen, higher temperatures speed up the processes or microbial activity while cooler temperatures slow things down. It should be noted however, that certain microbial processes (e.g. mineralization, nitrification, etc.) can appear faster in the fall than spring, even though soil temperatures are the same. This may simply be a reflection of a greater number of microorganisms in the soil after the growing season compared to after winter.

Surface applied urea N fertilizers, should not be applied during warm humid conditions, or on wet residues because of the high potential for N losses through ammonia volatilization. Light rainfall or even heavy dews can provide enough moisture for urea hydrolysis to occur but not enough water to move the urea into the soil, again resulting in a significant amount of N loss through ammonia volatilization.

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After hydrolysis of urea, the ammonium produced can be readily nitrified even when applied late in the fall and can be quite susceptible to denitrification or leaching in the fall through to the following spring.

Anhydrous ammonia applied in the fall does not nitrify as quickly due to the stunting of microorganisms in the anhydrous ammonia application band. However, spring applications would be expected to result in greater N use by the crop and lower levels of nitrate leaching through the soil.

Nitrate fertilizers are very soluble resulting in a high salt index which influences their rate and placement with respect to seed row or root system. Since N is already in the nitrate form, it is very mobile in the soil and more easily lost through leaching.

Due to the soluble nature of most N fertilizers, N is usually moved into the soil with incoming precipitation before runoff from the soil surface begins. In general, conditions that lessen the amount of infiltration of incoming precipitation would encourage N losses in runoff if soluble forms of N remain at the soil surface.

Soil Texture and the Effect of Surface Soil pH Soil texture impacts the retention and conversion of N in several ways. Typically sandy soils drain quickly and have a low CEC thus allowing the leaching of ammonium. Nitrification occurs under aerobic conditions and again this process would be more favorable in coarse-textured soils. Coarsetextured soils have a lower water holding capacity and therefore a greater potential to lose nitrate through leaching when compared with fine-textured soils. Some sandy soils, for instance, may retain only 1/2 inch of water per foot of soil while some silt loam or clay loam soils may retain up to 2 inches of water per foot.

In finer textured soils, there is usually a higher CEC, thus retention of ammonium and its leaching and nitrification rates are lower. Because fine-textured soils drain slower and retain more water than coarsetextured soils, the occurrence of anaerobic conditions is increased, which can give rise to greater losses of N through denitrification.

As noted under P.O. 1 above, urea converts to the ammonium form of N in the soil. The urease enzyme (present in soils, bacteria and crop residues) speeds the process. Surface-applied urea is subject to losses of ammonia. Losses increase with higher soil pH, more crop residues and with higher temperatures. Avoid urea applications when the fertilizer will remain on the soil surface for prolonged periods of time. Because clay soils tend to have higher CEC and a greater buffer capacity, they may retain more ammonium and experience less ammonia volatilization than coarser-textured soils when urea or other ammonium based fertilizers are surface applied.

Environmental Concerns in the Local Area (Surface and Groundwater) Since fertilizer N is either applied as, or is quickly converted to, soluble mineral N forms that are prone to leaching losses, it is extremely important to reduce the amount of residual fertilizer N in the soil at the end of the growing season. Ontario’s precipitation is relatively uniform throughout the year, although leaching potential is greatest in the non-growing season due to lower temperatures and limited plant growth resulting in less evapotranspiration. Applying only enough N fertilizer to meet crop requirements for a realistic yield goal, time of application and use of slow-release fertilizers are N management practices that will reduce N leaching.

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A variety of coatings can be applied to fertilizer particles to control their solubility in soil. Controlling the rate of nutrient release can offer environmental, economic and yield benefits. Coatings are typically applied to granular or prilled N fertilizer but multi-nutrient fertilizers can also be coated. Since urea has the highest N content of common soluble fertilizers, it is the base material for most coated fertilizers.

Anhydrous ammonia has the highest N content of any commercial fertilizer however handling NH3 requires careful attention to safety. Since it is very water soluble, free NH3 will rapidly react with body moisture such as lungs and eyes causing severe damage. Accidental escapes of NH3 to the atmosphere must be avoided. Emissions of NH3 are linked to atmospheric haze and changes in rain water chemistry. The presence of elevated NH3 concentrations in surface water can be harmful to aquatic organisms.

Crop Stage Urea can be used as a starter, broadcast or top-dress application and can be used in fertilizer mixes (dry or liquid). Advantages of urea are its high N content (45% to 46%), relatively low cost per lb of N, and rapid conversion to plant-available N. Disadvantages are lower safe rates of N, or N and potassium fertilizers that can be applied with or near the seed of many field crops. If the fertilizer is not being incorporated, other N sources (e.g. UAN, ammonium nitrate, calcium ammonium nitrate) are less susceptible to ammonium volatilization than urea.

Applying UAN onto crop foliage through streamer nozzles is acceptable although using flood jet or teejet nozzles can result in severe burning.

A solution containing dissolved ammonium sulphate is often added to post-emergence herbicide sprays to improve their effectiveness at weed control. This increases herbicide efficacy when the water supply contains significant concentrations of calcium, magnesium or sodium.

Competency Area 2 Determining the Right Rate of Nitrogen Performance Objective 3 Interpret how soil test nitrogen levels relate to crop yield response and potential environmental impacts.

Soils can vary greatly in their ability to supply N. Ontario’s soil N test measures the amount of nitrate in the soil and has only been calibrated for corn and spring barley. Typically most, if not all, of the nitrate N in the soil from the previous year has been immobilized, leached or denitrified before spring planting. Therefore, the amount of nitrate found in the soil in the spring arises from the mineralization of organic N to form ammonium and the nitrification of this ammonium to nitrate. The amount of nitrate in the soil is believed to reflect the amount of organic N in the soil that will be mineralized during the growing season and thus available N to the crop. Therefore, the higher the soil test N levels in the spring, the lower the crop response to and need for fertilizer N.

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As noted above, the amount of nitrate in the soil in the spring depends upon the activity of soil microorganisms and the amount of mineralizable organic N in the soil. Since temperature and moisture levels can impact microbial activity, the amount of nitrate found in the soil can also vary with weather conditions. Cool spring conditions will reduce the amount of nitrification in the soil, leading to an underestimation of the N supplying power of the soil over the growing season. Conversely, unusually warm springs can lead to greater nitrate formation and an overestimation of the soil N supply.

Other field activities can also cause changes to the nitrate levels of the soil which make the prediction of the soil’s N supply difficult. Incorporation of readily decomposable organic material with a large C:N ratio could result in the immobilization of nitrate and lower soil N test levels. Conversely, application/incorporation of materials with a low C:N ratio (e.g. legume plow down), or a source of both easily mineralizable organic N and ammonium (e.g. animal manure) could cause an increase in mineralization and nitrification resulting in elevated nitrate N levels and an over-estimation of the soil N that will be supplied to the crop during the growing season.

Many of the factors included in the general recommendations will influence the soil nitrate levels, so the recommendations for the nitrate-N soil test should be viewed as separate from the general N recommendations. Research is ongoing to find methods to incorporate the soil test into the general recommendations as an adjustment as well as to account for spring weather conditions.

Sometimes the fertilizer recommendations based on the nitrate-N soil test need to be modified based on application of N-containing materials after the collection of soil samples. Information will be provided with the test results on how to make appropriate adjustments.

The nitrate-N soil test has not been adequately evaluated for: • legumes or manure plowed down in the late summer or fall; • legumes in a no-till system; and, • soil samples taken prior to planting before the soil has warmed up significantly (i.e. in mid- to late April) In these circumstances, use the nitrate-N soil test with caution.

Providing that the nitrate-N soil test has adequately predicted the additional fertilizer N requirement of the crop there should be a lower risk of over fertilizing with N, and thus lower environmental impact due to N loss from the soil.

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Performance Objective 4 Discuss the environmental risk of applying nitrogen above economic optimums.

Crop responses to applied N fertilizer typically follow a concept referred to as the law of diminishing returns, where each increment of N added results in a successively smaller and smaller yield response to the applied N until no further yield response is observed as depicted in the figure below. Note, while corn yield response to applied N will typically level off, smaller grains will likely display yield reductions with excessive applications of fertilizer N. At some point along this response curve, the cost of the last increment of fertilizer added results in an equal value of yield response. In other words, the last dollar of fertilizer gave back a dollar worth of yield. This point is called the economical optimum rate of fertilizer N application (also known as the most economical rate). After this point, a dollar of fertilizer gives back less than a dollar in yield. The economical optimum rate of N for a response curve like the one below can be calculated by finding the point on the curve where the slope equals the price ratio (PR), as calculated by the equation: PR = $/kg fertilizer N

$/kg crop For most Ontario crops, the economical optimum rate of N fertilization often occurs at ~ 90%-95% of the maximum yield, depending upon the shape of the response curve and the PR. The amount of applied N fertilizer that enters the crop, follows a pattern similar to the diminishing returns in that at some level of fertilization, the additional increments of N fertilizer applied, above that level, result in less N entering the crop. One way to assess how well a crop is utilizing applied N fertilizer is to assess its N recovery efficiency (NRE). The NRE can be viewed as simply the amount of applied fertilizer N found in the harvested crop divided by the amount of N applied (see equation below).

NRE = (Amount of N in crop with fertilizer)-(Amount of N in crop without fertilizer)

Amount of fertilizer N added Generally speaking, NRE are usually around 40%-60%, depending on several factors such as source, timing and rate of N application. Fertilizer N applications above the economical optimum rate would be expected to have a lower NRE value, and thus a greater amount of residual fertilizer N remaining in the soil after crop harvest.

Studies have demonstrated that postharvest residual nitrate levels increase greatly when application rates exceed the amount required for optimum economic yield. The amount of this residual mineral N left in the soil after crop harvest is also a reliable indicator of the risk of loss through either leaching or denitrification.

Graph Source: Ivan O’Halloran, Ridgetown Campus, University of Guelph

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Under certain weather conditions, N can be lost from the soil between application and crop uptake especially in regions with moderate to high rainfall. Using the correct amount of N optimizes crop yield while minimizing loss of N to the environment.

Using excessive rates reduces profitability for the farmer and can result in excess nitrate being delivered to ground and surface water resources, or increases in denitrification and greenhouse gas production.

Performance Objective 5 Justify the considerations for nitrogen application rate based on: a. economics; b. weather and climate, including; i. temperature; ii. precipitation amount; iii. rainfall intensity; iv. precipitation patterns; c. crop type and growth stage.

Economics Ideally, fertilizer N application based on the economically optimum rate of N would be the most profitable for the farmer. Based on the PR as described in the previous P.O., one would consider reducing the rate of fertilizer N applied as PR increases (i.e. as fertilizer cost per unit of N increases or as the crop value decreases). Conversely, as the PR decreases the economical rate of N would increase. The difficulty with this approach is that one must use past yield responses to serve as a predictor of the current year’s crop response to N fertilization. This can lead to inaccurate predictions of the economical rate of N as crop responses to fertilizer N can vary with factors such as growing season conditions, N source, method of application and crop variety. Research studies suggest that variations typically observed in the year to year values of the PR would have much less impact on the rate of fertilizer N that should be applied compared to the changes in the economical rate of N based on differences in the crop response to fertilization from one year to the next. While this is an obvious limitation of this approach for making fertilizer recommendations, alternative approaches such as those based on yield goal are similarly impacted by the same factors.

Weather and Climate Nitrogen fertilizer can be lost from agricultural fields especially in regions with moderate to high rainfall. The risk of N loss will depend to some extent on the form of N applied and conditions after fertilizer application. Ultimately, the longer the applied fertilizer remains in the soil, the more likely it will be converted to nitrate and thus prone to leaching or denitrification losses if rainfall amounts or intensity result in water movement through the soil.

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The first period with a high risk of N loss is spring, when soils tend to be wet and before rapid crop growth begins to pull water out of the soil. This risk ends sooner with crops that begin rapid growth early in the spring, such as wheat and grass. Early spring application of N for summer crops, like corn, can result in loss of N and reduction in yield. One usually sees higher N application rates recommended for pre-plant applications due to these losses. If N is to be applied more than two weeks before planting, use of anhydrous ammonia is recommended as this may delay nitrification and reduce risk of nitrate leaching and yield reductions.

A second period of high risk for N loss can occur in late May and June. Urea hydrolysis and nitrification will have converted a significant amount of applied fertilizer N to nitrate. Even though rapid crop growth may have started, if heavy rains create saturated or near-saturated soil conditions for several days or longer, the combination of warm and wet soil conditions can lead to rapid N loss through leaching and denitrification. The denitrification risk is greatest on poorly drained soils.

Sidedress application of N or use of N stabilizers with pre-plant applications may reduce the risk of these losses.

The third period of high risk for fertilizer N loss is after the growing season when residual fertilizer N remains in the soil. Application rates above the economical optimum rate typically result in greater residual levels of fertilizer N in the soil and thus greater N losses. If one consistently has high residual soil N levels after crop harvest, reduction of future fertilizer rates is warranted.

Crop Type and Growth Stage In all crops, rapid uptake of N occurs during the maximum growth period. There is not much risk of N loss when fertilizer is applied at the beginning of the period of rapid growth as this is usually when soils are drier. Nitrogen application should be timed to provide adequate amounts of N when plants are actively growing and using N rapidly. Losses of applied N from fertilizer can be reduced by delaying application until the crop has emerged (side dressing). Split N applications, where some N is applied prior to crop emergence and the balance after emergence, can increase crop N-use efficiency and generally lower fertilizer N requirements on medium and fine-textured soils. While multiple N splits/application would in theory improve N use efficiency, no consistent benefit has been shown for many field crops, and additional application costs must be considered for the increased number of field passes.

Because the Rhizobia bacteria that infect legume roots normally supply adequate N to the host plant, well-nodulated legumes rarely respond to additions of N fertilizer. Occasionally, however, soybeans may respond to applications of N late in the season, presumably because N fixation in the nodules has declined significantly. Such responses are quite erratic though, and late-season applications of N to soybeans are not routinely recommended. The amount of atmospheric N fixed by non-symbiotic soil organisms varies with soil types, organic matter present and soil pH. Planting cover crops after harvest in the fall or between crops will capture or recover a portion of the residual N in the soil after main crop harvest and potentially help prevent N loss.

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Performance Objective 6 Justify the considerations for nitrogen application rate based on: a. soil characteristics including leaching; b. topography and runoff; c. crop conditions, including crop type and growth stage.

Soil Characteristics Losses of N from the soil generally occur with the mineral forms of N (i.e. ammonium or nitrate).

Leaching losses tend to be greater for coarser textured soils, while denitrification losses are greater for poorly drained and heavier textured soils. Compared to a silt loam soil, Ontario’s corn N calculator would generally increase N application rates on finer textured soils (clays, heavy clays, clay loams, silty clays and silty clay loams) and coarser textured soils (loam, loamy sand, sandy loam and sandy clay).

In southwestern and central Ontario, soil texture also affects the rate of fertilizer N recommended as a sidedress application on corn. For sand and loamy sand soils, the rate of N recommended as a pre-plant or sidedress remains the same. For other soil textures, sidedress N rates are decreased by 10% (sandy clay, sandy clay loam and sandy loam) or 20% (clay, clay loam, loam, silt loam, silty clay and silty clay loam).

Although the vast majority of soil N is in the organic N form, and one might expect greater soil N supply from soils with higher organic matter content, there is no specific recommendation for changing N rates based on soil organic matter. This may reflect the fact that the range of soil organic matter encountered in most field crop situations is insufficient to significantly impact the amount of soil N actually supplied to the crop. Improved soil conditions due to higher soil organic matter content improves conditions for crop growth thereby increasing crop N requirement which negates the additional N supplied from the soil.

Topography and Runoff Given that the soil’s supply of N to the crop comes almost entirely from the organic N pool, locations within a field with higher soil organic matter will likely provide more N to the crop. In most fields where there are substantial changes in topography, soil organic matter content increases as one moves down slope, reflecting the impact that water redistribution in the landscape has had on plant growth.

While upper slope positions have less soil N, those soils also tend to be shallower, with lower water holding capacity and drier. Thus, water typically becomes the limiting factor for crop yields and would predictably reduce the crop’s fertilizer nitrogen requirement under rain-fed conditions. Seasonal variations in rainfall amount and timing play an important role in determining variations in crop fertilizer N requirements with slope position. In irrigated systems, increased N application rates may be justifiable on upper slope positions.

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Since most N fertilizers are readily soluble, overland flow and N runoff is unlikely to be a significant issue as the N will likely be moved into the soil before runoff begins. If runoff is such that erosion has occurred, then any fertilizer N within the soil will have moved with the soil as well. Eroded areas are typically lower in soil organic matter, suggesting a greater need for additional N fertilizer. However, soil conditions (poor structure, water holding capacity, etc.) are usually what limit crop growth and thus additional fertilizer N is not warranted until the erosion problem has been addressed.

Crop Conditions See also P.O. 5 above.

For many crops, cumulative N demand usually follows an S-shaped curve, with a slow uptake rate during establishment and an exponential utilization in the vegetative and reproductive phases. Splitting N application is thus recommended by applying N in phase with crop demand, providing high soil-N concentrations at different periods needed for crop growth while minimizing the time for risk of leaching and denitrification losses. This is why one usually sees a lower N recommendation for planter and sidedress-applied corn versus pre-plant N applications. While it is expected that the amount of N required should be lower when using spilt applications, this has not always been observed when making multiple N applications throughout the growing season.

Crop colour appears to be the most reliable indicator of N stress for a range of crops during the growing season. Lighter colour indicates more N stress and a need for additional N. While repeated observations of N stress year in and year out would be indicative of a need for increased N rates, sporadic occurrences of N deficiency must be placed in the context of the growing season conditions, timing and severity of the stress, and the potential economic gain versus treatment cost if N was to be applied in-season. This approach only works for fertilizer applications made during the growing season. Most producers make in-season applications of N to wheat and forage grasses. Soybeans may also display pale green colour as seed reserves of N are depleted and nodulation is not yet fully developed. Application of N fertilizer will alleviate the N stress symptoms but is unlikely to impact yield and thus is a waste of resources. Sensors can be mounted either on tractor-based or high-clearance sidedressing equipment and can control application rates of sidedress N. However, numerous other stresses can cause differences in crop colour and chlorophyll content. Some corn varieties may respond to later in-season N applications although the full impact of such applications on total crop fertilizer N requirement, crop yields, crop N uptake and residual soil N is still under investigation.

Imbalanced plant nutrition, and particularly an excess of N, can lead to lush growth which is softer and is less able to withstand disease. Excess N can also lead to dense plant canopies which trap humidity within the canopy and create conditions where many fungal diseases can thrive.

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Performance Objective 7 Calculate nitrogen credits from: a. previous nitrogen application; b. soil organic matter; c. manure; d. biosolids and other organic amendments; e. irrigation applications (groundwater and wastewater); f. previous legumes.

Previous Nitrogen Application In the context of fertilizer N applications, one would consider the full amount of fertilizer N applied for the current crop to be credited towards the crop being planted. In general, issues regarding previous fertilizer N applications are likely limited to replant situations (as limited carry over of fertilizer N from one season to another is expected) or accounting for N applied either pre-plant or with the planter when sidedressing or top-dressing. Organic sources of N, such as manures, will provide a source of N in subsequent years as well. Based on the amount of manure organic N applied, an N credit would be calculated as 10% in the second year, 5% in the third year, and 2% in the fourth year. For example, for every 100 kg ha-1 of organic N applied in manure in 2016, we would calculate a residual manure N credit of 10 kg ha-1 in 2017, 5 kg ha-1 in 2018 and 2 kg ha-1 in 2019. The N credit for manure in year of application is discussed in the section pertaining to manure in this PO.

Compost Application.

Courtesy Christine Brown

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PROFICIENCY AREA II - Nitrogen

Soil Organic Matter While soil organic matter is the dominate pool of N in soil, the mineralization of this N to a plant available form can be affected by numerous factors. As such, there is no N credit given based strictly on soil organic matter content. Base N requirements for soil texture in different regions of the province are provided in Table 2.1. The table indicates a smaller influence of texture on corn N requirements in Eastern Ontario compared to other corn producing areas in the province.

Table 2.1. Soil Texture and Base N Requirements for Corn Base N Requirement Soil Texture

Metric

Imperial

Southwestern and Central Ontario

Eastern Ontario*

Southwestern and Central Ontario

Eastern Ontario*

Clay, heavy clay

53

1

47

1

Clay loam

40

1

36

1

Loam

32

1

28

1

Loamy sand

46

19

41

17

Sandy loam

38

19

34

17

Sand

52

19

46

17

Sandy clay, sandy clay loam

43

19

38

17

Silt loam

20

1

18

1

Silty clay loam

36

1

32

1

Silty clay

49

1

44

1

*Eastern Ontario includes Frontenac, Renfrew and counties to the East of them.

Chart source: Agronomy Guide for Field Crops, Publication 811, 2009, p.21 and 258.

Manure The best way of determining the amount of N from manure is to analyze a sample. Alternately, average values will provide an estimate of the nutrients available to the crop. Refer to the chart contained in Performance Objective 9, Proficiency Area 5, Manure Management.

The availability of manure N to the crop depends on the proportion of ammonium and organic N in the manure, as well as the timing of application and incorporation. The ammonium N in manure is chemically the same form of N as in many mineral fertilizers and is immediately available to the crop. Unfortunately, the ammonium form is also subject to loss by volatilization if not incorporated immediately. The balance of the N in manure is in the organic form, which becomes available to crops gradually through the process of mineralization as the organic compounds break down.

More precise estimates of available nutrients can be made by accounting for the actual timing and conditions for manure application, and the lag time before incorporation. Refer to the worksheet, Calculating Available Nutrients from Spring-Applied Manure Using a Manure Analysis, contained in Performance Objective 9, Proficiency Area 5, Manure Management.

As mentioned previously, organic N contained in manures can continue to supply N to a crop for several years after application

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Biosolids and Other Organic Amendments Since biosolids encompass a wide range of materials, their nutrient contents are also quite variable and, thus, it is essential (and required by law) that the nutrient content of these materials is known prior to application (see table below). As with manures, there are mineral and organic N forms in the biosolids that affect both the immediate and long-term N credit from these materials. Liquid biosolids from aerobic digesters or from lime stabilized biosolids tend to have lower available N levels (primarily due to lower ammonium N contents) than anaerobically digested materials. Dewatered biosolids would have a higher proportion of organic N as most mineral forms of N would be removed with the water. In general, one considers the mineral and organic forms of N in the biosolids to behave similarly to those found in manures.

Table 2.2. Ammonium Content of Various Biosolids Type

Ammonium

Municipal Biosolids Aerobic sewage biosolids

1.6%

Anaerobic sewage biosolids

35%

Dewatered sewage biosolids

12%

Lime Stabilized sewage biosolids

trace

Paper Mill biosolids

trace

Spent Mushroom compost

5

1. Ammonium content increases as liquid concentration increases.

2. Balance of nitrogen is in organic form.

Source: NMAN Software

Irrigation Application (groundwater and wastewater) This will require a water test to determine the level of N (usually nitrate-N) and application rates over the season in terms of acre inches of water applied. Typically, nutrients in water samples are measured in units of ppm. To calculate the amount of N applied, one needs to know the concentration of N in the water and the amount of water applied.

An acre-foot of water is 2,719,518 lbs., so for every foot of irrigation water one is adding approximately 2.72 x ppm of nutrient, or ~0.227 x ppm for every inch of irrigation water applied.

For example, if irrigation water contains 10 ppm NO3-N, then each foot of water applied would give ~27.2 lbs. ac-1 of N, or each inch of irrigation water supplies ~2.27 lbs. ac-1.

For metric units, each cm ha-1 of water weighs 100,000 kg, so 0.1 x ppm of nutrient is the kg ha-1 of nutrient applied. Using the above example, 1 cm of irrigation water with 10 ppm NO3-N would supply 1 x 0.1 x 10 = 1.0 kg ha-1 NO3-N. If the irrigation water contains significant quantities of NH4-N, a similar calculation can be performed.

Provincial recommendations currently do not consider an N credit based on N content in irrigation waters.

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PROFICIENCY AREA II - Nitrogen

Previous Legumes When sod containing perennial legumes such as alfalfa, birdsfoot trefoil and clover are plowed under, they supply an appreciable amount of N to the following crop. Table 2.3 below shows the reductions that should be made in N fertilizer applications to crops following sod containing legumes.

Table 2.3. Adjustment of Nitrogen Requirement Where Crops Containing Legumes are Plowed Down Type Type of Crop

For All Crops, Deduct From N Requirement kg/ha

lb/acre

Less than one-third legume

0

0

One-third to half legume

55

49

Half or more legume

110

100

Perennial legumes seeded and plowed in the same year

451

401

Soybean and field bean residue

02

02

1. Applies where the legume stand is thick and over 40 cm (16 in.) high.

2. F or all crops other than corn. For adjustments to corn fertilizer requirements, see Corn Nitrogen Rate Worksheet, on page 21 of the Agronomy Guide for Field Crops.

Chart source: Agronomy Guide for Field Crops, Publication 811, 2009, p.162.

Performance Objective 8 Discuss the use of technologies to make ongoing adjustments to the nutrient rates that may have been identified during the 4R nutrient management planning process such as: a. crop canopy sensors; b. normalized difference vegetative index (NDVI); c. post-season stalk nitrate; d. soil nitrate test; e. plant analysis.

Crop Canopy Sensors Advances in precision agriculture technology have led to the development of ground-based active remote sensors that can determine Normalized Difference Vegetation Index (NDVI). In simple language, this means variation in vegetation such as the crop canopy. For example, studies have shown that NDVI is highly related to leaf N content in corn (Zea maysL.). Remotely sensed NDVI is used to detect variability in the crop canopy to determine N status during the growing season for inseason site-specific N management.

Different crops and even varieties within a crop can differ in their basic reflective signatures as well as show different changes in reflectance in response to various stresses. Attempting variable application of N on say corn at sidedress can be very challenging. One approach is to supply a single row in each planter pass with N fertilizer at planting and this would presumably represent an N sufficient status. At sidedress time, the greenness of the unfertilized rows would then be compared to the fertilized row to PROFICIENCY AREA II - Nitrogen

51

determine the degree of N limitation in that location and vary the amount of N fertilizer applied based on the difference in greenness. The relationship between differences in greenness and crop fertilizer N needs has to be known and programmed into the variable rate applicator. One problem with this approach is the need to forgo application of starter N with the planter as this tends to mask the variations in soil N supply, making it difficult to distinguish large differences in greenness. No starter N can cause yield reductions in corn. Ontario research has also shown that crop yield response to applied N was poorly correlated to differences in corn crop greenness at sidedress.

Regardless of the system or method used, relationships between crop greenness and fertilizer N requirements are needed in order to predict fertilizer N application. These are crop and potentially variety specific and can be affected by other factors such as growing season conditions.

Normalized Difference Vegetative Index (NDVI) The Normalized Difference Vegetation Index (NDVI) is an index of plant “greenness” or photosynthetic activity, and is one of the most commonly used vegetation indices. Vegetation indices are based on the observation that different surfaces reflect different types of light differently. Photosynthetically active vegetation, in particular, absorbs most of the red light that hits it while reflecting much of the near infrared light. Vegetation that is dead or stressed reflects more red light and less near infrared light.

Likewise, non-vegetated surfaces have a much more even reflectance across the light spectrum.

Post-season Stalk Nitrate The post-season stalk nitrate test allows growers to conduct a “post-mortem” evaluation of the adequacy of their N program for the current growing season. The test is described as “post-mortem” because stalk samples are taken after the grain is physiologically mature. Given that this is a very late season test, the interpretation of the results offers no assistance in fine-tuning N management for the current year, but rather provides insight into N management options for coming years (i.e. if stalk nitrate-N levels were deemed excessive, and growing season conditions were normal, then one should consider lowering N inputs in that field the next time corn is planted assuming all other factors remain constant). One needs to consider other environmental factors that may have impacted the availability of N to the corn plant, the corn plant N requirement and concentrations of nitrate remaining in the stalk at the end of the season.

The basis for the test lies in the fact that corn plants deficient in N will usually remobilize stored N from the lower portions of the stalk and leaves to the developing grain, resulting in lower stalk N concentrations at the end of the season. Plants that take up excessive amounts of N (more than is needed for maximum yields) will contain excessive amounts of nitrate-N in the lower stalk sections by the end of the growing season, resulting in higher stalk nitrate-N concentrations.

The stalk nitrate test is probably best suited for identifying fields/situations where N supply was excessive (exceeded economical rate) and, thus, costly to the grower and possibly the environment.

Typical situations where N uptake may be excessive include: manured fields or fields following alfalfa that received additional (and possibly unnecessary) N fertilizer applications for the subsequent corn crop, or growing seasons where yields were reduced due to lower rainfall, or possibly early fall frost.

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PROFICIENCY AREA II - Nitrogen

Pre-plant Soil Nitrate Test (PPNT) The soil N test is a measure of the nitrate-N in the soil. Referring back to the N cycle diagram, you see that the nitrate in the soil comes from the nitrification of ammonium, which in turn comes from the mineralization of soil organic N. The soil N test thus uses the amount of N mineralized and nitrified up to the time of sampling to predict the amount of organic N that will be mineralized and supplied to the crop during the growing season. The difference between the estimated crop requirement for N and the predicted soil supply of N is the amount of fertilizer or available manure N that needs to be applied.

The pre-plant test measures the amount of mineral N (nitrate) in the root zone before planting and, in Ontario, the soil N test is calibrated only for corn and barley. The pre-plant test allows farmers to adjust N applications to meet the needs of each specific field. Cropping sequence significantly affects the amount of N in the soil available to corn. The pre-plant test is most useful in continuous corn, secondyear fields, and fields with a long history of manure applications but not recent manure applications or legume plow down. The soil N test is not recommended for these latter two scenarios due to the uncertainty of the amount of manure or legume N that has been converted to nitrate and measured by the soil N test, versus the mineralization of soil organic N. The pre-plant test is most useful on medium- or heavy-textured soils and during years when precipitation is normal or below normal. Below normal precipitation in autumn and winter can lead to higher spring pre-plant soil nitrate levels. Exceptionally cool, wet spring conditions can lower early season soil nitrate levels due to limited microbial activity in the soil.

Pre-Sidedress Soil Nitrate Test (PSNT) Sampling when the corn is 15-30 cm (6-12 in.) tall, before the application of sidedress N, has increased in popularity and is often the most reliable time for assessing fertilizer N requirements using the soil N test. This is referred to as the pre-sidedress N test (PSNT). By delaying sampling past the busy planting season, the PSNT allows more time for sampling and receiving results from the laboratory. More importantly, considerable evidence indicates that N recommendations based on this later sampling time are superior to those based on a planting time sample. This in large part is due to the fact that yearly differences in weather conditions affecting mineralization and nitrification of soil organic N tend to diminish as we move from early spring to early summer. Research is underway to improve the soil N test’s prediction for fertilizer N requirement by considering growing season conditions (e.g. precipitation and crop heat units).

Sometimes the fertilizer recommendations based on the nitrate-N soil test need to be modified. The N in manure or legumes applied or plowed down just before sampling will not have converted into nitrates and will not be detected by the soil test. Information will be provided with the test results on how to make appropriate adjustments based on the N credits for these sources of N. The nitrate-N soil test has not been adequately evaluated for: • legumes or manure plowed down in the late summer or fall; • legumes in a no-till system; and, • soil samples taken prior to planting before the soil has warmed up significantly (i.e. in mid- to late April) In these circumstances, use the nitrate-N soil test with caution.

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Plant Analysis Tissue, leaf or plant analysis can be used to: • determine the nutrient needs of established perennial crops such as tree fruit and grapes, and • confirm the diagnosis of visual symptoms of unusual plant growth or deficiencies.

For perennial crops, tissue sampling is often preferred over soil sampling because it is difficult to take soil samples in the root zone of perennial crops. Tissue analysis also helps show what nutrients are being taken up by the crop as opposed to what is available in the soil. This may mean that the nutrient limitation is not due to an inadequate amount of nutrient in the soil, but rather to soil conditions that are limiting the plant roots’ ability to absorb that nutrient from the soil. This, however, is not usually the case for N unless soils are waterlogged.

Plant analysis identifies a nutrient as being deficient when its concentration falls below a critical level for a given plant part, in the specific crop at a particular stage of plant development. In order to interpret the tissue analysis, the timing or stage of plant growth and the plant part being sampled is very important.

Used along with a soil test, tissue analysis can identify possible nutrient limitations or deficiencies.

Although a tissue analysis may indicate a nutrient could be deficient or limiting, it is not easy to make a fertilizer recommendation rate from a tissue analysis. As well, tissue analysis may not provide information in time for correction for annual crops in the current growing season.

Competency Area 3 Determining the Right Timing of Nitrogen Application Performance Objective 9 Discuss how the timing of soil nitrogen tests can impact test levels.

Given the precipitation patterns in Ontario, we typically expect the soil profile to leach completely over the fall to spring period, thus removing any residual nitrate N from the root zone. In finer textured soils, where leaching is less prominent, there is the risk of nitrate loses through denitrification. Thus, the amount of nitrate observed in the soil in the spring is likely due to the mineralization and subsequent nitrification of organic N in the soil. Since these processes are microbially mediated, earlier season measurements (i.e. pre-plant) will result in lower soil N test values than samples taken later in the season at pre-sidedress. As a result, for a given soil N test level, one would usually see a lower recommendation for N on corn if the sample was taken pre-plant versus at pre-sidedress.

Sampling shortly after manure application or legume plow down is likely only measuring a fraction of the N in these materials as there may have been insufficient time for mineralization and nitrification. For example, mineralization and nitrification of the applied manure N will depend upon the time interval between application and soil sampling as well as the weather conditions (precipitation, temperature) and method of application. Information will be provided with the test results on how to make appropriate adjustments. Similarly, sampling after application of a readily decomposable C source with a wide C:N ratio (> 25:1) is likely to reduce the amount of nitrate-N in the soil, and thus lower the soil nitrogen test values.

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PROFICIENCY AREA II - Nitrogen

The nitrate-N soil test has not been adequately evaluated for: • legumes or manure plowed down in the late summer or fall; • legumes in a no-till system; and • for very early pre-plant soil sampling done before the soil has warmed up significantly (i.e. in mid- to late April).

In these circumstances, use the nitrate-N soil test with caution.

Performance Objective 10 Estimate the environmental risks in the timing of applying nitrogen based on: a. climate; b. soil type; c. runoff; d. irrigation; e. leaching potential.

Although P is the main factor causing eutrophication (often associated with algal blooms, nuisance aquatic plant growth, low oxygen levels in water, and death of aquatic organisms), N lost from fertilizer and manure can make the problem worse. High ammonium-N concentrations in surface water can also be toxic to aquatic organisms and impair water for livestock or human consumption.

Excessive nitrate-N in surface and drinking water also spoils water quality. While we typically view nitrogen contamination of water to be a groundwater issue, tile drains divert leaching nitrates to surface water bodies and surface applied ammonium N sources can be lost with surface runoff if runoff occurs shortly after N application.

Climate Application of fertilizer or manure on frozen and/or snow-covered soil is not recommended because rapid snow melt or rainfall can move nutrients and other constituents from the nutrient sources to surface waters as meltwater movement into the soil is restricted. For materials applied at other times of the year, volatilization and leaching would be the likely pathway of N loss. Cool, wet and calm conditions reduce the risk of ammonia volatilization, especially of materials left on the soil surface with either a high ammonium or ammonium forming N content (e.g. urea). Soaking rains that are sufficient to move the N into the soil before runoff occurs will also lower volatilization losses. Light rainfalls following surface applied urea can result in higher ammonia volatilization losses. This occurs because there was sufficient water to dissolve the fertilizer and allow urea hydrolysis, but not enough to move the fertilizer into the soil. If the form of N applied was nitrate, or sufficient time after N application has allowed nitrification to occur, then heavy rains at this time would increase the risks of nitrate leaching and denitrification.

PROFICIENCY AREA II - Nitrogen

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As mentioned in P.O. 9, we experience a relatively even pattern of precipitation in Ontario. Given the lower temperatures and lack of significant plant growth in late-fall to spring period, the greatest risk of water movement and thus nitrate leaching through the soil would be in this period. For fall applied manures, the earlier in the fall the material is applied the greater the opportunity for N to be mineralized and nitrified before soil freezing. This increases the risk of nitrate leaching. As the soil moisture content increases, the risk of anaerobic conditions also increase and thus we would expect greater denitrification and greenhouse gas production.

While gentle rains after N application are typically desirable in most cases, especially if N materials are left on the soil surface, applications just prior to excessive rains that cause substantial leaching or runoff should be avoided.

One would expect better N utilization by the crop if timing of N application coincides with crop demand, which obviously is impacted by climate. Utilization of cover crops may be one method of immobilizing excess soil mineral N in the fall, although this depends upon cover crop plant species and cover crop biomass produced. Fall application of readily decomposable, high C:N ratio materials can also help reduce soil mineral N losses in the non-growing season.

Soil Type Coarse-textured soils have a lower water holding capacity and, therefore, a greater potential to lose nitrate from leaching when compared with fine-textured soils. Some sandy soils, for instance, may retain only 1/2 inch of water per foot of soil while some silt loam or clay loam soils may retain up to two inches of water per foot. Nitrate-N can be leached from any soil if rainfall or irrigation moves water through the root zone. Sandy soils typically have a lower CEC as well and thus leaching of ammonium-N can also be a problem in some circumstances.

Finer textured soils or soils that are poorly drained result in a greater risk of denitrification and the production of greenhouse gases.

Runoff To reduce the potential for nutrient runoff into surface water, fertilizers and manure should be injected or incorporated into the soil or be applied under conditions when runoff events are unlikely or at least unexpected. Fall and early winter applications are typically better for fertilizer and manure application than when the soil is frozen and/or snow-covered, although these times are associated with increased risk for leaching of the mineral N forms applied. Late-spring and summer applications typically represent the lowest risk of runoff and leaching N losses, provided application rates are appropriate in terms of plant uptake/requirement.

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PROFICIENCY AREA II - Nitrogen

Irrigation Nitrogen leaching during irrigation is directly related to the drainage volume. By increasing irrigation efficiencies, both the drainage volume and amount of N leaching are reduced. Both water management and N management are important in controlling N leaching. By using improved water management practices that control the amount of water applied and using the proper time to apply water (when the crop most needs and can utilize it), the irrigation efficiency is increased and N leaching is reduced. Applying only enough N fertilizer to meet crop requirements for a realistic yield goal, time of application and use of slow-release fertilizers are N management practices that will reduce N leaching.

The type of irrigation system utilized is also a factor. Drip and sub-surface drip irrigation systems offer better water application uniformity and accuracy and reduced soil surface wetting which minimizes nitrate leaching loss potential to groundwater.

Leaching Potential The ability of a soil to retain water depends upon the inherent water holding capacity of the soil and the current proportion of the water holding capacity that is already filled with water. Finer textured soils typically hold more water at field capacity than coarser textured soils and thus have a lower leaching potential. Wetter soils have more of the water holding capacity already filled and thus it takes less additional water to cause leaching to occur. If the profile is dry, normal fine-textured soils can hold up to two inches of available water and a gentle four-inch rain can completely infiltrate without any leaching. However, if the soil profile is at or near field capacity, there might be as much drainage as rain.

On an annual basis, leaching potential in Ontario is typically greatest in the fall to late spring period when soils are wettest due to cooler temperatures and limited plant growth. Mineral N applied or found in the soil during this period would be at the greatest risk of leaching and thus management practices should be adopted that attempt to minimize mineral N soil content at this time.

Performance Objective 11 Estimate the risks of applying nitrogen on saturated, frozen, or snow covered soils.

Applications to frozen ground are at higher risk for runoff and loss of those nutrients. When the soil is frozen, water is not able to infiltrate into the soil profile and the water and nutrients can runoff to adjoining properties or waterways. Applications on snow will also likely see soil conditions that are either frozen or saturated, again leading to increased risks of runoff or leaching. Ammonia volatilization can also occur when ammonium based fertilizers or materials with high ammonium contents are left on the surface of frozen soils. Applications of nitrate-containing materials to saturated soils increase both the risk of nitrate leaching as well as denitrification.

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Performance Objective 12 Discuss how the timing of nitrogen application is dependent upon the nutrient source.

Drilled with the Seed This method consists of placing the fertilizer with the seed in the seed row. Drilling fertilizer with seed in excess of recommended rates can cause seedling damage and reduce yields. Depending upon the equipment used, there can be a large variation in the concentration of fertilizer adjacent to the seed. Greater spreading of the fertilizer and seed and lower rates of fertilizer, reduce the likelihood of seedling damage. A double disc press drill places the seed and fertilizer close together in a narrow furrow. A disc, air seeder or hoe drill can scatter the seed and fertilizer, depending on the opener used.

Wider spacings between rows increase the concentration of fertilizer in each seed row thus reducing the safe rate of fertilizer that can be applied on an area basis.

Placing fertilizer with seed optimizes efficiency; however rates of N fertilizer need to be kept within safe limits to prevent reduced germination and seedling damage due to ammonia toxicity and/or salt burn.

Since sources of K fertilizer are also quite soluble and have a relatively high salt index, one needs to consider both the amount of N and K applied with or near the seed. Aside from the high ammonium formation and increase in soil pH, some sources of urea may also contain sufficient quantities of biuret which would decrease seed germination and seedling health. Urea application with the seed is usually restricted to 10 kg N ha-1 for spring oats and barley, and is not recommended for other field crops.

Diammonium phosphate (18-46-0) is likely the next most damaging N source to place with the seed due to its high, free ammonium content, with recommended safe rates of 20 or 30 kg N ha-1 for spring oats and barley on coarse soils (sands, sandy loam) and finer textured soils (loams, silts, clay loams), respectively.

For most field crops, it is unlikely that the entire crop requirement for N can be applied with the seed, and thus the bulk of the N application should be applied either before or after seeding, or banded away from the seed.

Aside from N source, several other factors affect the safe N rates applied with the seed such as crop type (sweet corn is very sensitive to seed placed fertilizer and seed placed fertilizers are not recommended on soybean, peas, beans and flax), row spacing (wider rows mean low safe rates), seed and fertilizer spread, soil texture (higher rates on finer texture soils), and soil moisture.

Side Band Placement This method consists of placing the fertilizer in a narrow band 2” to 3” to the side and/or 2” to 3” below the seed during seeding. The efficiency of side banding is equivalent to placement with seed and higher rates can be used safely. Nitrogen requirements of most crops can be met without causing seedling damage when solution or dry fertilizer is placed at least 2” from the seed row. Similar to seed placement restrictions, urea or ammonium based fertilizers pose the greatest risk to plant damage and so safe application rates of N with these sources is lower than other N sources. Again, there is a need to limit the amount of salt applied in the band so safe rates should consider both the amount of N and K being applied. Higher rates can be applied with narrower row spacings and moving the band further from the seed can increase the rate of fertilizer that can be applied in the band, but may limit the effectiveness of other fertilizer nutrients such as P.

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PROFICIENCY AREA II - Nitrogen

Anhydrous ammonia cannot be placed in or near the seed row. However, equipment has been modified to allow anhydrous ammonia to be applied at seeding time in a band or other arrangement that is separated from the seed. The anhydrous ammonia should be separated from the seed by at least 2” to 3” and placed below and to the side of the seed or to the side of the seed. It should not be applied directly below or above the seed. The anhydrous ammonia tends to follow the furrow upward, so attempts at placing it below the seed will likely lead to seed damage. Again, the safe application rate will depend upon soil texture and crop type.

Mid-row Banding This method places fertilizer between every seed row or every second seed row as part of the seeding operation. The fertilizer is banded with knives, discs or coulters to a depth of 3” to 4”. This system is an efficient method of N placement, which allows the application of high rates without risk of damage to germinating seedlings. It is generally suited for liquid fertilizer sources (e.g. 28% UAN) or anhydrous ammonia and as the band is a greater distance from the crop row, the rate of N application is of lesser concern in terms of crop damage.

Banding into Soil Prior to Seeding This method places the fertilizer below the soil surface in a band behind a shank at a depth of 3’” to 6”. It is often referred to as “deep banding”. Band spacings should not exceed 18” when applying N fertilizer. The efficiency of this method of N placement in spring is equal to side banding or seed placing fertilizer. Fall banding of fertilizer N sources would likely lead to greater N losses and reduced nitrogen use efficiency by the crop, regardless of fertilizer material used. Deep banding of nitrate N sources could result in increased risk of leaching or denitrification, especially if applied long before planting.

Anhydrous ammonia should be applied only when soil conditions permit a good seal behind the applicator shanks. Seeding can be done immediately after anhydrous ammonia application, provided there is at least a 4” vertical separation of the injection point and the seed. Crop emergence may be slightly reduced directly over the anhydrous bands, particularly for small seeded crops and if soils are sandy or dry. However, plants will tiller or branch and yield will not be affected. The ammonia bands should be perpendicular to the direction of seeding.

Surface Banding This application method places a band or stream of liquid fertilizer on the soil surface. The equipment used includes fertilizer floaters and field sprayers outfitted with dribble nozzles or streamer bars.

Surface banding improves N efficiency as compared with broadcast methods because volatilization and contact with residues and possible immobilization, are reduced. The liquid stream also penetrates a crop canopy better than a broadcast application and, as a result, more fertilizer reaches the soil surface. Fertilizer materials that are high in ammonium, or ammonium forming, and increase soil pH near the fertilizer (e.g. urea) run the risk of greater ammonium volatilization losses.

Nesting This method uses a spoke wheel injector to place regularly spaced pockets or nests of liquid fertilizer into the soil. N losses by volatilization are minimized as fertilizer N is placed within the soil.

Disturbance of soil and crop residue is minimal and post-seeding applications may be made into the growing crop.

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Broadcast and Incorporated Granular or solution fertilizer is broadcast on the soil surface and incorporated into the soil with a tillage implement. Nitrogen fertilizers, especially urea and liquid or dry fertilizers containing urea, should be incorporated as soon as possible to minimize gaseous losses by volatilization. As the fertilizer material is spread relatively uniformly over the soil surface, application of agronomic rates are of little to no concern in terms of salt or ammonia damage.

Broadcast without Incorporation This method usually results in the least efficient use of spring-applied fertilizer N. Fertilizer left on the soil surface increases the risk of loss by runoff, erosion, ammonia volatilization (especially with fertilizers containing urea) and immobilization by crop residue. This is the most commonly used method to fertilize established pasture or hay land and is frequently used in zero tillage production.

If urea is surface applied and not incorporated (either by rain or tillage), N losses to the air (as ammonia) can approach 40% of the applied N. In addition, a rapid pH increase after application caused by hydrolysis of urea can result in ammonia release that can damage seedlings if the urea is applied too close to the seed.

Ammonium nitrate (34-0-0) is a better N source than urea (46-0-0) for broadcast applications without incorporation. Losses of urea are higher than losses of ammonium nitrate under conditions favouring volatilization (e.g. high temperatures and high soil pH). Loss of urea can be minimized by applying during periods of low temperature or just before it rains. Treating urea with a urease inhibitor will delay volatilization losses for up to 14 days.

Nitrogen - Granular Courtesy Fertilizer Canada

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Performance Objective 13 Discuss the opportunities that split application offers for 4R nitrogen management.

Dividing total N application into two or more treatments can more specifically match N supply with a plant’s ability to utilize nutrients. Split application can be an important component of 4R nutrient planning by addressing right rate and right time.

Depending on soil type, climate, agronomic practices and other factors, N fertilizer can be vulnerable to loss. Denitrification, leaching and volatilization impose costs that include lost productivity and negative environmental impact. Split-applying N fertilizer is one way to confront these challenges.

When a crop’s total N requirement is supplied with a single pre-plant or at-planting application, most of the N must “wait” for the target crop’s future needs and that means the window for potential loss remains open longer.

By postponing a portion of the N treatment until the crop is better able to utilize the nutrient, plants take up the N more quickly and efficiently. That means growers get more from their fertilizer investment and fertilizer losses that can contribute to environmental concerns are lessened. When all of the N is supplied ahead of crop growth, more of that N is susceptible to denitrification, leaching or volatilization.

Split application offers efficacy benefits on a wide range of crops and forages but its management must be considered on a crop-by-crop basis. The timing of post-planting N applications is especially critical.

The target species must be immature and growing to provide time for the N to be absorbed and metabolized in order to have the most efficient yield or quality impact. In the case of corn, for instance, all of the N should be delivered to the plant before ears are set. In wheat, the second application of N generally is best made 10 days to two weeks prior to the jointing stage when leaf tissue elongates to form a stem and the plant’s N requirement increases as it begins its reproductive phase. Because of a need for continuous, in-season production, forages especially benefit from split-applying N. All crops, however, have different nutrient requirements.

Split application should not exceed total test-based N recommendations. While split-applying N can enhance efficiency, it does not change what the plant needs and should not be used to exceed recommendations. Those recommendations should always be based on reasonable yield goals derived and developed from research applicable to a given growing region.

The downside for split applications is that wet conditions may prevent timely treatment. Also, dry conditions can prevent fertilizer from reaching crop roots and extra fuel costs from additional trip through the field must be considered.

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Performance Objective 14 Discuss how cover crops can affect nitrogen availability in follow-up cash crops and supplemental nitrogen application timing.

Good stands of actively growing cover crops, including legumes such as red clover, will sequester significant amounts of soil mineral N. Cover crops following winter wheat have reduced the level of nitrate left in the soil in October and November by 50% compared to where no cover crop was planted. This results in less nitrate-N available to be lost over winter.

Under optimal growing conditions, non-legume cover crops (e.g. ryegrass, cereal grains) can take up substantial amounts of N. Oilseed radish has been reported to contain up to 100 kg/ha of N in aboveground growth under optimal growing conditions.

Although non-legume cover crops can sequester a significant amount of N, subsequent corn yields may not be increased to the same extent as following legume cover crops. To date, it has been difficult to show a consistent reduction in N fertilizer requirement for crops grown following a non-legume cover crop.

Table 2.4 Adjustment of Nitrogen Requirement Where Legumes Ploughed Down Type of Crop

kg/ha

lb/ac

• less than 1/3 legume

0

0

• 1/3 to 1/2 legume

55

50

• 1/2 or more legume

110

100

Perennial legumes seeded and ploughed in same year

78 for field corn 45 all other crops

70 for field corn 40 all other crops

Soybean and field bean residue

30 for field corn 0 all other crops

27 for field corn 0 all other crops

Established forages

Chart source: Soil Fertility Handbook, OMAFRA Publication 611, p. 122.

Cover crops vary widely in the timing of N mineralization. Oilseed radish and spring cereals tend to start to release N early in the spring when it may be subject to losses. Some cover crops, like ryegrass, are extremely resistant to breakdown. Although they absorb significant quantities of N, little is released to the next crop during the growing season. In some instances, cover crop residues with high C:N ratios can, in the following year, lead to immobilization of soil mineral N thus lowering the N available to the subsequent crop.

In addition, there are circumstances where cover crops can inhibit the growth of the following crop in other ways. A heavy layer of crop residue can keep the soil cool and wet in the spring, slowing crop germination and development as well as slowing nutrient mineralization. It may also physically impede the operation of planting equipment, reducing the stand and harbor pests like slugs or nematodes which can harm the crop. However, cover crops protect the soil from wind and water erosion and some species help to reduce the number of pests including nematodes.

The above content was adapted from the Soil Fertility Handbook, OMAFRA Publication 611, p. 124.

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Performance Objective 15 Evaluate the principles, appropriate use and impact to timing of nitrogen applications for: a. urease inhibitors; b. nitrification inhibitors; c. controlled-release nitrogen products; d. slow-release nitrogen products.

Typically, N is not applied as the crop needs it but rather in larger applications at set periods in crop growth. In some cases, applying all N at pre-plant does not result in optimal use of N. As well, N is subject to environmental losses through volatilization, denitrification, leaching and runoff. Consider the particular soil and cropping system and evaluate which N losses may be occurring and hindering fertilizer use efficiency.

Biological and chemical inhibitors are sometimes added to fertilizer to temporarily enhance or disrupt very specific soil reactions. Nitrification inhibitors are additives which slow the conversion of ammonium to nitrate in soil, which may reduce the possibility of nitrate leaching or denitrification.

Urease inhibitors, another class of additives, can be used with urea fertilizer to temporarily delay its transformation to ammonium by inactivating urease, a common soil enzyme. This delay can reduce ammonia volatilization losses to the atmosphere, especially when urea is applied to the soil surface.

Since the formation of ammonium has been delayed, the subsequent formation of nitrate is also delayed.

Urease inhibitors provide potential benefits in no-till or reduced tillage systems when surface applying N and on soils that favour ammonia loss. Its use can provide some flexibility for application timing.

However, urease inhibitors have little value if the conditions for urea hydrolysis or volatilization are not present.

Nitrification inhibitors can be valuable: on tile drained soils when leaching potential is high; on wet or poorly drained soils; with fall fertilizer applications; when applying ammonium fertilizers; and, in no-till systems. It is not necessary when applying sidedress and does not work well on coarse-textured soils.

With the low cation exchange capacity, ammonia can leach out of the zone containing the inhibitor.

Again the effectiveness of nitrification inhibitors depends upon conditions that would encourage both the nitrification of ammonium and the loss of nitrate through either leaching or denitrification.

Slow-release and controlled-release fertilizers can be useful for improving nutrient use efficiency. There are several mechanisms for controlling nutrient release from a fertilizer particle. The most common is when a protective coating of polymer or sulphur is added to a fertilizer in order to control the dissolution and release of nutrients. Typical release rates range from a few weeks to many months.

Other slow-release fertilizers may have low solubility or a resistance to microbial decomposition to control nutrient release. Each of these products may be well suited to a specific set of conditions but that does not mean they are well suited to all conditions. Specific products must be matched with the proper soil, crop, and environmental conditions in order to get maximum benefit. Nitrogen is the nutrient generally targeted for controlled-release, but there are circumstances when sustained release of other nutrients is also desirable.

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Competency Area 4 Determining the Right Placement/Method of Application for Nitrogen Performance Objective 16 Discuss how the source of the nitrogen will determine the best placement or method of application.

Urea (46-0-0) A dry material in granular or prilled form urea rapidly hydrolyzes to NH4+. Losses increase with higher soil pH, more crop residues and with higher temperatures.

Urea can be used as a starter, broadcast or top-dress application and can be used in fertilizer mixes (dry or liquid). If urea is surface applied and not incorporated (either by rain or tillage), N losses to the air (as ammonia) can approach 40% of the applied N. Within one day after application, about 66% of urea-N is hydrolyzed to ammonia-N; all within one week. When not incorporated, significant N loss by volatilization can occur until approximately 1/2 inch of rain has fallen.

In addition, a rapid pH increase after application caused by hydrolysis of urea can result in ammonia release that can damage seedlings if the urea is applied too close to the seed. Conversion of ammonium to nitrate results in the formation of hydrogen ions (H+), so, like most N fertilizers, repeated urea applications will cause a reduction in soil pH over time.

Ammonium nitrate (34-0-0) A dry material in granular or prilled form, in which half of the N is as nitrate and half is as ammonium.

Used for direct application and in the production of N solutions (see below); broadcast or sidedress. It can be left on surface or incorporated into soil. When applied to the soil, ammonium nitrate dissolves in the soil water and separates into ammonium and nitrate, both of which can be absorbed by plants.

It is slightly more quickly available to plants at low temperatures than urea but, under normal growing conditions, there is no practical difference.

Calcium ammonium nitrate (27-0-0) Calcium ammonium nitrate is applied the same as ammonium nitrate however it acidifies soil only half as much as ammonium nitrate.

Urea-ammonium nitrate solution (UAN) (28-0-0 to 32-0-0) A mixture of ammonium nitrate, urea, and water. Urea supplies about half of the N that may be subject to volatilization loss. The other half of N is supplied by ammonium nitrate. Once applied, N solution behaves exactly like dry urea and ammonium nitrate.

UAN can be broadcast or placed in the starter band. If broadcast, UAN should be incorporated into the soil as the urea portion is subject to volatilization. However, because of its lower percent of N in urea and ammonium form, volatilization losses per pound of N from UAN will be lower than for urea.

Banding with drop nozzles has been found to minimize volatilization losses.

Avoid applying UAN onto crop foliage as severe burning will result. To minimize injury, do not spray on vegetation. For post-emergence application, use a directed spray or dribble between the rows.

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Nitrogen – Prills Courtesy Fertilizer Canada

The benefits of this product are its uniformity, ease of storage, handling and application. Like urea, UAN will lower the pH because of conversion of ammonium to nitrate and subsequent release of H+.

Anhydrous ammonia (82-0-0) A high-pressure liquid that turns into a gas when released. Anhydrous ammonia is applied by injecting it into the soil where it vapourizes and dissolves in the soil moisture. It must be injected six to eight inches deep on friable, moist soil. N loss by volatilization can occur if not properly injected or if soil is too wet or too dry at application. To avoid vapour losses to the air, the anhydrous band must be placed deep enough in the soil that the injection slot closes over.

Ammonium sulphate (21-0-0) A dry crystalline material in which the N is all in the ammonium form. It is used for direct application and blended complete fertilizers. It can be broadcast or sidedressed, left on surface or incorporated into soil. It is useful for surface broadcast applications as there is less risk of ammonia volatilization.

It is a good starter N source and, where S is needed, ammonium sulfate is a good source of S. Calcium nitrate (15-0-0) It is highly hygroscopic and may liquefy completely when exposed to air with a relative humidity above 47%. One method of application is dissolved in irrigation water.

Potassium nitrate (12-0-44) A specialty fertilizer used for direct application and in blended fertilizers.

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Performance Objective 17 Discuss how the time of the year, climate, tillage practices, and residue management will impact the proper placement or method of application.

Time of Year If N fertilizer sits on or in the soil long before plant uptake, there is potential for N loss to air, groundwater, or immobilized by bacteria and fungi. These losses are a direct financial loss to the producer, may decrease yields, and may have negative environmental and health effects.

Immobilization of the fertilizer N is not necessarily a loss as this N will eventually mineralize due to microbial biomass turnover. However, the timing of this mineralization may be too late to provide any benefit for the crop it was intended to fertilize. The closer fertilizer application can be timed to maximum plant uptake, the smaller these potential losses.

Split fertilizer applications allow nutrient management to be adjusted for the current year yield potential and can reduce losses. Timing the application so nutrients are available prior to maximum nutrient demands, which come before plants reach their maximum size, is critical. The second of split applications on small grains should be applied prior to early tillering, though actual timing will depend on a variety of factors including soil nutrient levels and starter fertilizer amounts. In oilseed crops, the optimal time for supplemental in-season fertilization would be before or during branching. Because timing of spring fertilizer applications should ideally be based on plant growth stage, rather than calendar date, the optimal date of a second application, or top-dressing, will vary with the crop and year. In crops started later in the spring, top-dressing would occur later in the season. A cooler spring will also delay timing of a second application due to delayed growth and nutrient uptake.

Regardless of the crop and year, adequate nutrients are necessary early in growth for maximum production and to ensure that N is available for good grain or seed fill. Wheat plants take up approximately 70% of their necessary N and phosphorus by early heading. Over 50% of the N and phosphorus used for grain fill comes from the stem, leaves, and head of the plant, rather than directly from the soil. If the nutrients are not available for early plant growth, then yield may be compromised, and efficiency of fertilizer use is reduced. Both are financial losses to producers. However, applying N fertilizer too early, for example in early fall when the soil is still warm and active, can also cause fertilizer loss. The use of slow or controlled-release N products may more closely match plant uptake and reduce potential N loss. Fall application of N fertilizers to bare soils should be avoided.

Ammonium based fertilizer N applications in the summer under hot, dry conditions can also lead to excessive ammonia volatilization if the fertilizer is not incorporated or injected into the soil.

Climate Nitrogen losses due to leaching, gaseous loss, immobilization and weed growth are probably higher for fall-applied than for spring-applied N. These losses may be greater if the N is applied too early in the fall (prior to mid-September) or when soil temperatures at the 4” depth are greater than 5°C. Loss of N accounts for much of the difference in efficiency between fall and spring applications. Under dry soil conditions, the efficiency of ammonium or ammonium based fertilizers banded in late fall can approach that of spring banded because potential losses due to leaching or denitrification are low. Efficiency of fall-applied N can be substantially lower under excessive moisture conditions in spring or fall and/ or an early fall application before soils have cooled to 5°C as significant amounts of nitrification will occur. Regardless, fall applied N fertilizers for next season’s crop are typically at much greater risk for N losses than spring applied fertilizers and should be avoided.

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Poorly drained soils or depressions have high potential for loss of nitrate-N. These losses can be minimized through proper placement and timing of N. Time and method of application should be based not only on the needs of the crop and potential losses from the soil, but also on coordination of the soil fertility program with an efficient overall farm management system. Select a time and method of N application that permits preparation of a good seed bed, conserves soil moisture, aids in prevention of soil erosion, allows for timeliness of operations and maximizes net returns.

Tillage Practices Conventional Tillage Nitrogen can be broadcast or banded in conventional tillage systems. Broadcast fertilizer is spread over the whole soil surface usually with a truck or tractor-pulled spreader. Nitrogen is usually mixed into the soil by tillage which helps improve efficiency rates. Nitrogen may be lost if not worked in properly. Banded fertilizer is applied in a narrow strip below the soil surface. This may be done at planting time or sidedressed after the crop is up. Sidedressed N is more efficient than broadcast because it is placed close to where the roots are at a time when the crop can make the best use of it.

Mulch Tillage Because soils in mulch till systems tend to be a little cooler and wetter in spring than in conventional tillage systems, there may be a benefit to using starter fertilizer. The balance of the fertilizer can be broadcast and incorporated with secondary tillage passes as in the moldboard system. Rates of application depend on the soil test. Nitrogen fertilizer must be injected or incorporated into the soil.

No-Till and Ridge Till Systems The absence of tillage allows nutrients to accumulate in the top layers of soil. Nutrient levels below this layer tend to be lower than conventionally-tilled fields. Nitrogen applications on cereals are similar to conventionally-tilled fields. Nitrogen for corn should be placed below the residue. Avoid broadcasting urea-based products. Many no-till farmers believe approximately 30 kilograms per hectare (27 lbs per acre) of N should be in the starter fertilizer. No yield benefits result, but early crop appearance is improved. Coulters are usually added to equipment to improve fertilizer placement. In ridge till, N is knifed into the ridge away from corn roots or in the valley. Liquid N can be dribbled behind the disc hillers on the cultivator where it will be covered with soil thrown by the sweeps.

Residue Management Broadcasting UAN solution (28-0-0 to 32-0-0) is not recommended when residue levels are high because of the potential for the N in the droplets to be absorbed by the residue. Dribbling the solution in a surface band will reduce this and knife or coulter injection will eliminate it. Limited research suggests that the same conclusions probably apply for grass hay or pasture. Surface banding of N can be useful mainly when UAN solution is the N source of choice on a field with substantial residue cover, and the producer does not want to inject the solution.

The above content was adapted from: Scharf, P. C., Lory, J. A., Best Management Practices for Nitrogen Fertilizer in Missouri, University of Missouri Extension and University of Missouri-Columbia, 2006.

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Performance Objective 18 Discuss how crop stage will determine the placement or method of application.

At or Near Time of Seeding Nitrogen fertilizer applied at or near time of seeding is usually the most effective for increasing yields.

However, seeds are living organisms (even in the dry state) and being exposed to ammonia can reduce viability. Both ammonia vapours in the soil air and ammonia dissolved in the soil water cause damage from ammonium fertilizers. The damage can commence as soon as the ammonia contact takes place and is intensified by the duration of exposure, the ammonia concentration, crop species’ tolerance and seed metabolic activity (stage of germination).

The safest application method for high rates of high ammonium content fertilizers is to place them away from the seed by physical separation (combined N, P products) or by pre- or post-plant application (straight N products). For the lower ammonium content fertilizers, e.g. MAP, close adherence to the safe rate limits set for the crop species and the soil type is advised.

After Seeding Under moist conditions, applying N up to two weeks after emergence is a good alternative to applying N in the fall. However, if N fertilizer is broadcast without incorporation on dry soils, N utilization may be delayed. If urea (46-0-0) is used, gaseous N losses may occur. Ammonium nitrate (34-0-0), while not readily available, is the preferred N source for broadcast application after seeding.

Leaf burn may occur if N solution is sprayed onto leaf surfaces. Canola, flax, corn and sunflowers are particularly susceptible to damage. In trials, cereals at seedling stages have been sprayed with N solution at 40 lb N/ac with minimal damage and no reduction in yield.1 Leaf burn is minimal under cool, wet conditions. Rain or irrigation immediately following N application washes all leaf surfaces free of fertilizer and results in little or no damage. Broadcasting granular fertilizers does not cause damage unless the foliage is wet.

N fertilizers can be applied to row crops following crop emergence and is usually referred to as “side dressing”. Fertilizers banded into the soil should be applied at least 6” to 8” from the row in order to minimize root pruning. Use care so that plants are not damaged by equipment. Applying N fertilizer between every second row (similar to mid-row banding) is referred to as “skip row application”.

Mid-season applications of N fertilizer can also be used to increase the protein content in grain.

Nitrogen application to the growing crop through irrigation water has greater efficiency than placing all the N at the time of seeding.

Fall-applied Nitrogen on cereals does not usually give yield and/or protein increases as great as those obtained when equal amounts are added in spring. However, in many cases, the differences in yield between fall and spring applications are small, particularly under dry soil conditions. Losses due to leaching, volatilization, denitrification, immobilization and weed growth are usually higher for fallapplied N and account for differences in yield and protein content.

1. Loewen-Rudgers, L., K. McGill, P. Fehr, G, Racz, A. Ridley and R. Soper. 1977. Soil fertility and fertilizer practices. In Principles and Practices of Commercial Farming. pp. 61-89.

Faculty of Agriculture. University of Manitoba.

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Performance Objective 19 Discuss the role of nitrogen technology products and the considerations for nitrogen placement or method of application for: a. urease inhibitors; b. nitrification inhibitors; c. controlled-release nitrogen; d. slow-release nitrogen products.

Refer also to Performance Objective 15 above.

Slow-release N products may be considered when attempting to reduce environmental losses from volatilization, denitrification, leaching, and runoff. There are three general categories: uncoated controlled-release, coated controlled-release, and bio-inhibitors. The controlled-release products slowly break down N into the soil. Bio-inhibitors are not really slow-release. They inhibit microbial processes that convert N into plant available form which is more susceptible to environmental losses. The term “fertilizer technologies” encompasses all types of products.

Uncoated slow-release products include: • Urea-formaldehyde reaction products which decompose in the soil by chemical or biological processes or a combination of both; • Isobutylidene diurea which relies solely on soil chemical processes to break down product; and, • Inorganic salts such as magnesium ammonium phosphate.

Coated, slow-release N products include: • Sulphur-coated urea which releases N through oxidation of the S coating (used on turf), and • Polymer-coated or poly-coated urea. Water moves in through the coating to dissolve the urea. The N diffuses out through the porous polymer membrane. The polymer coating is unique to each manufacturer.

Coated, slow-release products can reduce N leaching on sandy soils and may provide an alternative to split application of N. Bio-inhibitors include urease and nitrification inhibitors.

Urease inhibitors help to control volatilization and can be added to urea or mixed with UAN. If rainfall occurs within two to three days of N application, a urease inhibitor may prevent volatilization losses which can be 15% to 20% of N applied. Urease inhibitors chemically inhibit the activity of the soil enzyme urease. This slows the breakdown of the urea, providing time for rainfall to move urea into the soil. The effect of these products can remain for two weeks or more depending on conditions. Warm temperatures and wetter conditions cause urease to repopulate faster. As noted under P.O. 15, urease inhibitors provide potential benefits in no-till or reduced tillage systems when surface applying N and on soils that favour ammonia loss. Its use can provide some flexibility for application timing. However, urease inhibitors have little value if the conditions for volatilization are not present.

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Nitrification inhibitors delay the conversion of NH4+ to NO3- for two to four weeks depending on the soil pH and temperatures. There may be value in using a nitrification inhibitor when NO3- losses are high from leaching or denitrification. Nitrification inhibitors can be beneficial: on tile drained soils when leaching potential is high; on wet or poorly drained soils; with fall fertilizer applications; when applying ammonium fertilizers; and, in no-till systems. It is not necessary when applying sidedress and does not work well on coarse-textured soils. With the low cation exchange capacity, ammonia can leach out of the zone containing the inhibitor.

Performance Objective 20 Evaluate the role of fertigation in 4R nutrient management planning.

Fertigation is the application of fertilizer via the irrigation system. Relating to the 4R philosophy, fertigation helps address the right rate, time and place of nutrient management planning. Fertigation provides increased flexibility of fertilizer application as nutrients can be applied any time during the growing season according to the crop’s needs and growth stage. Nutrients can be applied uniformly over the field if the irrigation system distributes water uniformly. It also allows for small dosage application. Leaching and water contamination is less likely with fertigation because less fertilizer is applied at any given time and the application can correspond to the peak crop requirements.

Fertigation can also be very targeted to the root zone depending on the type of irrigation system used, e.g. subsurface drip. The water goes into the root zone of the plants where it can be absorbed and used quickly. This mitigates runoff and leaching.

There are disadvantages to using fertigation as well.

• Fertilizer distribution is only as uniform as the irrigation water distribution.

• Lower cost fertilizer materials such as anhydrous ammonia often cannot be used.

• With overhead irrigation systems, fertilizer placement cannot be localized as in banding.

• Many fertilizer solutions are corrosive and can damage the irrigation system.

• Excessively wet conditions may limit the opportunity to apply fertilizer N when needed, or enhance its risk of loss when applied.

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Competency Area 5 Environmental Risk Analysis for Nitrogen Performance Objective 21 Discuss how to use water quality vulnerability assessment tools (e.g. Source Water Protection Plans) on a site specific basis for nitrogen nutrient planning.

Tools such as Source Water Protection Plans identify the water resources, their use and the potential factors that would affect the quantity and quality of that water. Assessment reports consider aspects such as watershed characteristics (e.g. land use and activities, area, soils, bedrock geology, physiography, topography, etc.), water flow or water budgets (precipitation, runoff, usage, etc.), current condition of water resources and the potential threats to the quality of the water based on the activities and characteristics of the land within that watershed.

Vulnerable areas for surface water are areas such as those near drinking water intake pipes (also known as Intake Protection Zones or IPZs). The IPZs can be mapped and given vulnerability scores.

IPZs with greatest vulnerability usually require greater diligence to avoid contamination.

Similarly, Groundwater Vulnerability Analysis looks at underground sources of drinking water and risks to the quality of this water. In general there are three main areas that are vulnerable to contamination: Wellhead Protection Areas, Highly Vulnerable Aquifers and Significant Recharge Areas. Again the report would identify and map these vulnerable areas and assign vulnerability scores.

Activities within areas of high risk of N movement or vulnerability of contamination should require a more judicial use of fertilizer N. A better understanding of the pathways and timing of N loss to the water resources will enable one to adjust method, timing, source and rate of fertilizer application to reduce losses and improve crop use efficiency. In extremely sensitive areas, it may mean a substantial change in the rate of N applied or cropping system used to achieve this goal.

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Performance Objective 22 Evaluate nitrogen management decisions using a water quality vulnerability assessment (e.g. Nitrogen Index).

The Nitrogen Index is a tool for reducing the risk of nitrate contamination of groundwater. It evaluates the vulnerability of nutrient management practices with respect to the movement of nitrates. The N Index combines source and transport factors to assess the risk of nitrate movement to groundwater on a field-by-field basis.

The N cycle is complex and factors contributing to both nitrate sources and transport often interact.

When manure N converts to the nitrate form, it will move through the soil with water rather than bind to soil particles.

Source Risk Factor The net amount of nitrate in the soil following harvest may have come from: • N applied for growing the current year’s crop; • nutrients applied after crop harvest; • residual N in crop residues, especially legumes; and, • mineralized N and nitrified materials from soil organic matter.

In the case of N applied for the current year’s crop, it is the amount of N applied in excess of crop requirements that is of most concern. For nutrients applied after harvest, as with fall application of manure, there is an increased risk of nitrate movement to groundwater. The timing and method of application and the type of manure will influence risk.

Transport Risk Factor The transport factor evaluates the opportunity for nitrate to move down, with water, through the soil to groundwater. In Ontario, crops are normally removing more water from the soil during the growing season than is being added as precipitation, so there is no leaching during the growing season except under abnormally wet conditions.

The fall, winter and early spring usually bring more precipitation than evaporation so water can move down through the soil profile. This is the reason we are concerned with the amount of nitrate in the soil after the growing season when there is no crop to absorb the nitrate and the risk of loss is high. Cover crops grown after crop harvest help reduce this risk of loss by taking up nutrients and holding them in organic form until spring.

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Performance Objective 23 Be able to evaluate how changing a specific nitrogen management strategy will affect the outcome of a risk assessment.

It cannot be stressed enough how understanding the N cycle, seasonal hydrology and crop N utilization is paramount to being able to identify how a change in a specific N management strategy will affect the risk of N loss. Below is a risk-assessment table for N addressing the potential for nutrient losses based on soil type, when fertilizer is being applied, the form of N, placement, and whether it is being stabilized to prevent loss. It serves as an example of several scenarios, but is by no means a complete picture of the possible scenarios that could occur in the field.

Table 2.5 Nitrogen Risk Assessment Situation

Risk

Approaches

Leaching

Avoid fall application, make split applications beginning in the spring using inhibitors, slow-release forms, fertigation

Fall application to silt loam or clay loam

Denitrification, leaching

Ammonia application with an N stabilizer although still less efficient than spring applied fertilizers.

Pre-plant applications to silt loam or clay loam

Denitrification, leaching, runoff, volatilization

Ammonia with a N stabilizer, PCU, methylene urea, urea with stabilizer, incorporation or injection of fertilizer

At planting surface application with no-till

Volatilization, runoff, denitrification

Urea with stabilizer, PCU, methylene urea, UAN and stabilizer

Sidedress application or fertigation

Wet weather preventing timely application

Pre-plant or at-planting split applications using inhibitors or slow-release formulations

Sandy soils

Source: University of Nebraska, accessed from www.notillfarmer.com

Best management practices for reducing the risk of N losses include continuous no-tilling, cover crops, precision tillage as needed to remove compaction, installing vegetative buffers as protection against extreme erosion events, and physically placing nutrients in the soil so they are less vulnerable to runoff.

Sandy soils have a higher risk of N leaching losses. Soil will move with heavy rainfall events, even with no-till, but it can be minimized by utilizing cover crops with active roots to keep the soil intact and adopting structures that minimize runoff. Many farmers have adopted conservation tillage, leaving larger amounts of residue on the surface that reduces soil movement and runoff.

Physical structures like terraces, contour farming, grassed waterways and buffer strips reduce runoff as well, but on large-acreage farm operations with big equipment, these practices can be an inconvenience.

The benefits of cover crops are being increasingly promoted. Besides protecting the soil against erosion, they scavenge and recycle excess nutrients, such as residual nitrates, out of the soil and contribute carbon back into the soil, which improves soil health and soil and nutrient resiliency.

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When managing N, growers have tools to reduce the risk of N loss while increasing N-use efficiency.

The first recommendation is to move fall applications to the spring, and spoon-feed N over several applications, such as pre-plant, at-plant and sidedress.

Second is stabilizing N and manure applied to protect it from loss. Urease inhibitors limit urea hydrolysis and thus control loss of ammonia as a gas from urea and UAN. Nitrification inhibitors (nitrapyrin and dicyandamide) can be used to control conversions of ammonia forms of N to nitrate, limiting nitrate loss through leaching or denitrification.

Slow-release forms of N are available which parse out nutrients into the soil environment to match the uptake needs of the crop, reducing risk of loss. Slow-release products include sulfur-coated urea, polymer-coated urea, sulfur and polymer-coated urea, methylene urea plus triazone, and others.

Performance Objective 24 Evaluate management strategies that will reduce nitrogen loss to surface water and groundwater, ammonia volatilization, and nitrous oxide emissions.

The diagram below illustrates the various forms and pathways that N can take as it cycles through an agricultural production system. Before N can be used by plants, it must be converted into forms that are available to plants; this conversion is called mineralization. The plants take up these mineral forms through their root systems and form plant proteins and other organic forms of N. Livestock eat crops and produce manure, which is returned to the soil, adding organic and mineral forms of N to the soil, which can be used again by the next crop. Ideally, it would be most economically and environmentally beneficial to keep all the N in this tight cycle for food production. In reality, however, some leakage occurs. Where there is too much N leakage, there can be environmental harm.

Source: International Plant Nutrition Institute

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Nitrate Nitrate (NO3-) is an extremely soluble form of N. It does not bind with the surfaces of clay minerals nor does it form insoluble compounds with other elements that it encounters when moving through the soil. Because nitrate is soluble, it can readily move with soil water toward plant roots to be taken up by them. However, if there is a large amount of water entering and passing through the soil root zone, NO3- can be carried by percolating water beyond the soil root zone. This downward and lateral movement through the rooting zone and possibly towards agricultural tile drainage systems is driven by water infiltrating from rainfall or a snow melt. This leaching occurs at times of the year or at points in a field where the amount of rainfall or snow melt exceeds evapotranspiration and the soil is near its saturation capacity. Under such conditions, soil water moving downwards recharges groundwater or contributes to tile drain flow, carrying nitrate with it.

Nitrite Nitrite (NO2-) is produced naturally as part of the process of converting ammonium into nitrate. It seldom accumulates in the soil, since the conversion from nitrite to nitrate is generally much faster than the conversion from ammonium to nitrite. Nitrite moves much like nitrate in the soil and groundwater zones.

Ammonia Ammonium (NH4+) bonds to negatively charged surfaces of soil particles, clay in particular. The concentration of ammonium in the soil is generally quite low (<1 mg/kg) because it is quickly converted to nitrate under conditions that are favourable for mineralization. The exception is where high rates of an ammonium fertilizer (anhydrous ammonia, urea or ammonium sulphate) or high rates of manure are applied. Occasionally, heavy rainfall washes this concentrated ammonium from the field into surface water. A small part of this ammonium can be converted to dissolved un-ionized ammonia (NH3), which can harm fish. The conditions that favour ammonia generation are alkaline pH and warm water temperatures.

Volatilization and Denitrification Natural losses of N, in addition to nitrate leaching, occur through ammonia volatilization and denitrification. Ammonia volatilization occurs when manure or an ammonia-based fertilizer (particularly urea) are applied to the surface of the soil without incorporation into the soil. Over half of the ammonium N from manure can be lost to the air under warm, dry conditions, greatly reducing the fertilizer value of the manure. However, the concentrations of ammonia released are not high enough to cause direct environmental or human health harm outdoors, and most of the ammonia is re-deposited within a few hundred metres of where it was released.

Denitrification is a natural process where microbes in the rooting zone use the oxygen in nitrate where there is not enough air in the soil. This process converts the nitrate into gaseous forms of N, primarily N2, but also into nitrous oxide (N2O) or nitric oxide (NO). Conditions that favour dentrification within the rooting zone are soils with slow internal drainage (fine-textured soils), an ample carbon supply and saturated soils from shallow groundwater or heavy rainfall. Denitrification can also occur in the groundwater and surface water environments. In some aquifers, denitrification can result in the complete conversion of nitrate to dissolved N gas, which is not harmful to aquatic ecosystems or human health. However, denitrification cannot be counted on to eliminate all the N leaching to groundwater or running off to surface water.

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Management Strategies • Match N applications with crop requirements; use the spring or pre-sidedress soil N test where available (e.g. for corn and barley).

• When planning nutrient applications, account for N contributions from other sources, such as: green manure crops, previous crop rotations, manure or biosolid application.

• Apply most of the N just before the time of maximum crop uptake (e.g. sidedress corn).

• Split applications of N through techniques such as fertigation.

• Practice crop rotations to make efficient use of N and maintain healthy soils.

• Establish cover crops as needed to “tie up” any excess N at the end of the season.

• Practice timely tillage to incorporate manure, balancing the risk of soil compaction with the losses of N to the atmosphere if the manure is not incorporated quickly.

• Avoid applying manure near surface water or on steeply sloping land.

• Keep application rates low enough to prevent runoff.

• Mix manure into the soil as soon as possible after applying it.

• On tile-drained land, keep application rates of liquid manure below 40 m3/ha (3,600 gal/ac) or pre-till the field before applying it. This will help prevent the movement of manure directly to tile through cracks or earthworm channels.

•U se buffer strips and erosion control structures to filter runoff before it enters surface water. Buffer strips in riparian zones have proven to reduce nutrient movement off the field into nearby surface water sources. Buffer strips consume excess nutrients before they flow into surface water and enhance opportunities for groundwater denitrification.

Buffers include: riparian buffers, filter strips, grassed waterways, shelterbelts, windbreaks, living snow fences, contour grass strips, cross-wind trap strips, shallow water areas for wildlife, field borders, alley cropping, herbaceous wind barriers, and vegetative barriers. Birdseye view of an agricultural landscape with riparian forest buffers and other types of conservation buffers. Photo source: USDA NRCS.

Performance Objective 25 Compare the differences in the geographic scale, soil, topography, and location of watersheds (e.g. national, regional, local) on the environmental impacts of nitrogen on surface and groundwater resources.

Generally, aquifer vulnerability is represented by soil-drainage characteristics, the ease with which water and nutrients can seep to groundwater, and the extent to which woodlands and riparian areas are interspersed with crop land. Whether nitrates actually enter groundwater, depends on underlying soil and/or bedrock conditions, as well as the depth to groundwater. The risk of N leaching into groundwater occurs particularly where the soil is sandy, gravelly, or shallow over porous limestone bedrock. If depth to groundwater is shallow and the underlying soil is sandy, the potential for nitrates to enter groundwater is relatively high. However, if depth to groundwater is deep and the underlying soil is heavy clay, groundwater contamination from nitrates is not likely.

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Performance Objective 26 Discuss the role of nitrogen in the eutrophication process and the potential consequences of eutrophication.

Environmental concerns arise when N is leached into groundwater or delivered as runoff during rainfall events to streams, rivers, and lakes. Excess nutrients in aquatic systems continue to act as fertilizer and can stimulate the growth of plants and algae leading to oxygen deficient conditions. This is known as eutrophication.

In extreme cases of eutrophication, microscopic algae present in the water grow to densities so high that they reduce the light available to rooted plants living on the bottom. This shading effect may prevent photosynthesis causing the plants to die, resulting in the loss of important habitat for fish and other organisms. Greater production of algae may also lead to an increase in the frequency and duration of periods of low dissolved-oxygen concentration known as hypoxic events, which can cause further damage to the system as conditions do not support enough oxygen to sustain fish and other aquatic creatures.

Nutrient-enriched aquatic systems sometimes become dominated by noxious species of algae that form floating surface scums called blooms. Some of these algal species produce toxic substances that can negatively impact other plants and animals, including humans.

For many years, eutrophic conditions in inland freshwater systems have been attributed to excessive inputs of phosphorus rather than N. With higher concentrations of readily available P in surface waters, N may also contribute to the growth of aquatic plants and algae. In salt water systems, both N and P contribute to eutrophication.

Performance Objective 27 Discuss the role of nitrogen in drinking water standards.

The Ontario Drinking Water Standards (ODWS) set 10 mg/L (10 parts per million) nitrate as N (NO3--N) as the maximum allowable level for drinking water in Ontario. Medical researchers concluded that a concentration of 10 mg/L in drinking water is appropriate to avoid blue-baby syndrome in human infants. Recent research suggests that consistently high levels of nitrate in surface waters can harm some forms of aquatic life, particularly amphibians.

For nitrite as N (NO2-), the ODWS set 1 mg/L (1 part per million) as the maximum level for drinking water in Ontario. Nitrite levels in drinking water should not exceed this value. The Canadian guideline for aquatic water quality has an upper limit for nitrite of 0.06 mg/L (60 Âľg/L or parts per billion).

While nitrite is much more toxic to aquatic life than nitrate, nitrite tends to convert quickly to nitrate.

Unlike nitrate and nitrite, ammonia is not a human health concern in drinking water at the levels typically observed in the environment. However, it is toxic to fish at high concentrations. The Provincial Water Quality Objective (PWQO) for dissolved un-ionized ammonia is 20 Âľg/L.

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PROFICIENCY AREA III

PHOSPHORUS

Competency Area 1 Determining the Right Source of Phosphorus Performance Objective 1 Discuss the most common sources of phosphorus used in Ontario.

Ammonium Polyphosphate The most common ammonium polyphosphate fertilizers have a grade of 10-34-0 or 11-37-0.

Polyphosphate fertilizers offer the advantage of a high nutrient content in a clear, crystal-free fluid that is stable under a wide temperature range and has a long storage life. A variety of other nutrients mix well with polyphosphate fertilizers, making them an excellent base for complete mixed fertilizers. They can also be used as carriers for micronutrients that may be needed by plants, although these may need to be in a chelated form to prevent formation of insoluble sludges.

In polyphosphate fertilizer, 50% to 75% of the P is present in chained polymers. The remaining P (orthophosphate) is immediately available for plant uptake. The polymer phosphate chains are primarily broken down to the simple phosphate molecules by enzymes produced by soil microorganisms.

Commercial fertilizer sources include monoammonium phosphate, diammonium phosphate, fluid ammonium, triple superphosphate, and some registered materials manufactured from biosolids.

Manures from beef, dairy, swine, poultry and other livestock generally supply large quantities of phosphorus when they are land-applied. Advisors need to know how to calculate the available and total amount of phosphorus contained in manures. Biosolids may supply considerable P, and may be applied as non-agricultural source material (NASM) under a NASM plan approved by the Ministry of Agriculture, Food and Rural Affairs, or as fertilizers if the product is registered with the Canadian Food Inspection Agency.

Monoammonium phosphate (MAP) Monoammonium phosphate (MAP) is a widely used source of P and N. It has the highest P2O5 content of any common solid fertilizer (48% to 61%). Its N content is 10% to 12%. Granular MAP is water soluble and dissolves rapidly in soil if adequate moisture is present. Upon dissolution, the two basic components of the fertilizer separate to release NH4+ and H2PO4-. Both of these nutrients are important to sustain healthy plant growth. The pH of the solution surrounding the granule is moderately acidic, making MAP an especially desirable fertilizer in neutral and high pH soils.

Agronomic studies show that there is no significant difference in P nutrition from various commercial P fertilizers under most conditions. Granular MAP is applied in concentrated bands beneath the soil surface in proximity of growing roots or in surface bands. It is also commonly applied by spreading across the field and mixing into the surface soil with tillage. In powdered form, it is an important component of suspension fertilizers.

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There are no special precautions associated with the use of MAP. The slight acidity associated with this fertilizer reduces the potential for NH3 loss to the air. MAP can be placed in close proximity to germinating seeds with minimal concern for NH3 damage. Band placement of MAP protects the P from soil fixation and facilitates a synergism between ammonium and phosphate uptake by roots. When MAP is used as a foliar spray or added to irrigation water, it should not be mixed with calcium or magnesium fertilizers. A high purity source of MAP is used as a feed ingredient for animals.

Diammonium phosphate (DAP) Diammonium phosphate (DAP) is the worldâ&#x20AC;&#x2122;s most widely used P fertilizer. It is popular because of its relatively high nutrient content and its excellent physical, handling and storage properties. The standard grade of DAP is 18-46-0. Fertilizer products with a lower nutrient content may not be labeled as DAP. The high nutrient content of DAP reduces handling, freight, and application costs. DAP fertilizer is an excellent source of P and N for plant nutrition. It is highly soluble and thus dissolves quickly in soil to release plant-available phosphate and ammonium. An alkaline pH develops around the dissolving granule. As ammonium is released from dissolving DAP granules, volatile ammonia can be harmful to seedlings and plant roots in immediate proximity. To prevent the possibility of seedling damage, care should be taken to avoid placing high concentrations of DAP near germinating seeds. The ammonium present in DAP is an excellent N source and will be gradually converted to nitrate by soil bacteria, resulting in a subsequent drop in pH. Therefore, the rise in soil pH surrounding DAP granules is a temporary effect. This initial rise in soil pH neighboring DAP can influence the micro-site reactions of phosphate and soil organic matter. There are differences in the initial chemical reaction between various commercial P fertilizers in soil, but these dissimilarities become minor within weeks or months, and are minimal as far as plant nutrition is concerned. Most field comparisons between DAP and monoammonium phosphate (MAP) show only minor or no differences in plant growth and yield.

Monoammonium Phosphate (MAP) Courtesy Fertilizer Canada

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Some of the polyphosphate will decompose without the enzymes. The enzyme activity is faster in moist, warm soils. Typically, half of the polyphosphate compounds are converted to orthophosphate within a week or two. Under cool and dry conditions, the conversion may take longer. Since polyphosphate fertilizers contain a combination of both orthophosphate and polyphosphate, plants are able to use this fertilizer source very effectively. Most P-containing fluid fertilizers have ammonium polyphosphate in them. For most situations, the decision to use dry or fluid fertilizers is based on the price of nutrients, fertilizer handling preferences, and field practices rather than significant agronomic differences.

Some liquid fertilizers have been formulated to contain 100% orthophosphate, rather than polyphosphate. These are agronomically equal to ammonium polyphosphate.

Triple Superphosphate (TSP) Triple superphosphate (TSP) was one of the first high analysis P fertilizers that became widely used in the 20th century. Technically, it is known as calcium dihydrogen phosphate and as monocalcium phosphate, [Ca(H2PO4)2.H2O]. It is an excellent P source, but its use has declined as other P fertilizers have become more popular.

TSP has several agronomic advantages. It has the highest P content of dry fertilizers that do not contain N. Over 90% of the total P in TSP is water soluble, so it becomes rapidly available for plant uptake.

As soil moisture dissolves the granule, the concentrated soil solution becomes acidic. TSP also contains 15% calcium (Ca), providing an additional plant nutrient. A major use of TSP is in situations where several solid fertilizers are blended together for broadcasting on the soil surface or for application in a concentrated band beneath the surface. It is also desirable for fertilization of leguminous crops, such as alfalfa or soybeans, where no additional N fertilization is needed to supplement biological N fixation.

The popularity of TSP has declined partly because its total nutrient content (N + P2O5) is lower than in ammonium phosphate fertilizers.

Performance Objective 2 Discuss considerations to determine the right source of phosphorus based on: a. crop type and cropping system; b. c limate (temperature, precipitation, leaching, and runoff patterns); c. soil texture and the effect of soil pH; d. e nvironmental concerns in the local area (surface and groundwater); e. crop stage.

Crop Type The primary consideration is ensuring food safety for crops grown for direct human consumption.

Manure and improperly managed compost can be a potential source of pathogen contamination. For fresh market fruits and vegetables, allow at least 120 days between the application of manure and harvest. Proper composting of manure results in sufficient heating to reduce the level of most pathogens (OMAFRA Publication 363).

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Cropping System Consider the phosphorus needs and the application opportunities for the next crop in the rotation as well. For example, corn and cereals consistently show greater response to starter fertilizer than soybeans, so allowing soybeans to utilize the residual fertility from other crops in the rotation has agronomic merit. The source needs to be economical for the amount required. Where risks of runoff are high, the source needs to be one that can be mixed with the soil or placed below the surface in such a manner as not to increase risks of erosion. When applying sources with a large volume of liquid, such as liquid manures, risks of surface runoff and leaching to tile drains through macropores should be controlled.

Soil Texture Soils high in clay have the greatest risk of runoff and of macropore flow to tile drains, and thus require materials that can be mixed into the soil or applied in subsurface bands.

Soil pH Avoid applying diammonium phosphate in bands near seedlings. Monoammonium phosphate or triple superphosphate are much more suitable for band application near the seed row in such soils. Soils with pH below 5.5 or above 7.5 may tend to have high capacity to fix phosphate in unavailable forms.

Applying agricultural lime to raise the pH of acidic soils will improve P availability as well as provide other benefits for crop growth. In such soils, banding should be the first option, if P fixation is the issue, with over-application of organic P a second option. Organic sources of P may be preferred, if available, because large amounts of P can be supplied at relatively lower cost, and the organic matter may block fixation sites, increasing the availability of the applied P. Local Environmental Concerns In watersheds where phosphorus loading reduction is a high priority, soil test levels are high, and manure P is in surplus to crop removal, manure P either needs to be exported out of the watershed, or its production needs to be reduced through livestock feeding strategies or herd reductions. In watersheds where P loading reduction is a high priority, and soils have high runoff potential, it is particularly important to use P sources that can be injected, subsurface applied, or incorporated immediately following broadcast application.

Crop Stage As a nutrient, phosphorus is most often limiting the early growth of crop seedlings, and moves only slowly through the soil matrix. Therefore, it is best applied before planting, mixed into the soil, or at planting, banded near the seed row. For crops with high P requirements, like potatoes, some benefit can be obtained by applying part of the P application just prior to hilling, allowing the hilling operation to mix it with soil that is placed near the growing plants. Liquid manure application rates need to avoid saturating the soil with water from just before planting through the growing season.

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Competency Area 2 Determining the Right Rate of Phosphorus Performance Objective 3 Interpret how soil test phosphorus levels relate to crop yield response and potential environmental impacts.

P loss in runoff

Crop Yield

The general relationship of soil test P to crop yield and P loss in runoff is shown in the figure to the left.

Information more specific to Ontario soils is shown on the right. The critical value of soil test, beyond which response to phosphorus is less frequent, is commonly accepted as 20 ppm for corn in Ontario soil test recommendations.

Critical value for crop yield

Low

Medium

Optimum

High

As soil P increases so does crop yield and the potential for P loss in runoff. The interval between the critical soil P value for yield and runoff P will be important for P management.

Relative yield of corn versus soil test phosphorus from 18 site-years in an Ontario study conducted by Philom Bios and Dow Elanco (1993-1994). Adapted from Publication 611, OMAFRA.

As soil test levels increase, the concentration of dissolved phosphorus in runoff and drainage water increases. A study of Ontario soils (Wang et al., 2010) found that phosphate concentrations in runoff water (arising from artificial rainfall applied at 75 mm per hour) rose linearly with soil test phosphorus, whether by Olsen or Mehlich-3 methods, and that the best predictor of dissolved P concentrations in runoff was the ratio of phosphorus to aluminum in a Mehlich-3 extract. The linear relation predicted that dissolved P in runoff would increase by 0.00275 mg/L for each 1 ppm increase in Olsen soil test P. Another study of the same Ontario soils (Wang et al., 2012) found that dissolved phosphorus in drainage water leached through the soil (by adding 10 mm of artificial rain to soil cores previously wetted to field capacity) began to increase sharply at soil test levels higher than 48 ppm Olsen or 112 ppm by Mehlich-3.

The potential for phosphorus loss is related to other factors as well. Proper interpretation of the soil test as an indicator of risk of environmental impact requires the context of a phosphorus index accounting for all sources of phosphorus, and transport factors governed by landscape, soil hydrology and connectivity to water bodies.

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Performance Objective 4 Evaluate how different soil test phosphorus extraction methods affect the interpretation of crop yield response and potential environmental impacts.

Laboratories may report values for soil test phosphorus other than Olsen-P, the extractant recommended for Ontario soils. These values may include Bray P1, Mehlich-3, and others. Recommendations for crop nutrient need in Ontario are based on a calibration of crop response to the Olsen P level. The general trend is that results from all of the extractants increase as soil fertility improves, but each extractant has a unique relationship to crop response, and there is less or no public data relating values from other extractants to crop response.

Regarding potential environmental impacts, the two references given above for Performance Objective 3 (Wang et al., 2010 and 2012) provide information relating values from several different extractants, including Olsen-P, Bray P1 and Mehlich-3, to phosphorus concentrations in runoff and leaching water.

Again, each extractant has a unique relationship to impact, in this case, one component of risk of phosphorus loss.

The important point for both crop response and environmental impact is that interpretation must be based on published evidence, and is specific to each extractant. The accuracy of each extractant will vary with soil conditions, and their interaction with the extractants. This is particularly true in alkaline soils, where the acidic extractants (Mehlich-3 and Bray) can be neutralized by free carbonates and produce erroneous results.

Performance Objective 5 Estimate the environmental risk of applying phosphorus above crop response optimums.

Application of phosphorus at rates higher than needed for crop response can lead to increases, or buildup, of soil test P. Higher soil test P levels are one factor considered in the Phosphorus Index (OMAFRA, 2005), and generally will increase the risk rating, depending on the current soil test level and the level of transport factors. Higher rates of phosphorus application also directly increase risk of loss, particularly when the source is surface applied without incorporation.

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Performance Objective 6 Justify the considerations for phosphorus application rate based on: a. soil characteristics including leaching; b. topography and runoff; c. crop conditions, crop type, and growth stage.

Soil Characteristics Recommended phosphorus application rates generally do not adjust for soil characteristics other than soil test level.

Soils more prone to leaching (sandy soils) do not necessarily lose much phosphorus by leaching, since phosphorus is adsorbed to soil particle surfaces or precipitated as calcium or magnesium phosphates in soils with reasonable pH levels. Leaching of phosphorus can be an environmental impact of concern in soils that have been built up in soil test P such that P sorption has been saturated.

Vertical movement of P to tile drains (sometimes referred to as leaching) has been documented in medium to fine-textured soils where macropores (either cracks from soil drying or biopores such as earthworm burrows) provide pathways for runoff diverted from the surface to the tile drains.

Topography and Runoff In soils highly prone to surface runoff or to macropore flow to tile drains, loss of dissolved phosphorus can be a concern when high rates of soluble forms of phosphorus are surface applied without mixing into the soil. Topography and soil texture influence the potential for surface runoff. While losses tend to decrease when rates are lowered, the influence of placement and timing of application can be even more influential.

Steeply sloping fields can also be susceptible to soil erosion, leading to high losses of particulate phosphorus if suitable practices are not put in place (reduced tillage, no-till, cover crops, soil erosion structures).

A young windbreak that will one day offer protection to the sandy soils of the Town of Erin, Wellington County.

Courtesy Credit Valley Conservation

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Crop Conditions, Crop Type, and Growth Stage Phosphorus application rates may be based on crop removal of phosphorus in order to maintain soil test P at optimum levels. If so, recommendations for rate should consider a reasonable estimate of crop yield potential, and use its estimated nutrient content to calculate anticipated crop removal of phosphorus with the products harvested from the field. Phosphorus is normally applied at or before planting, and thus growth stage is not a consideration for most crops. A few exceptions include potatoes, which can benefit from a broadcast phosphorus application just before hilling, and perennial forages, which often receive a maintenance application after each cut. Research at the University of Guelph showed that there was no difference in crop response between multiple applications or annual applications of P and K. From a risk of loss perspective, P should be applied to forages after first or second cut to match the season with lowest risk of surface runoff and provide adequate time for applied P to bind with the soil before runoff occurs.

Source: International Plant Nutrition Institute

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Performance Objective 7 Calculate phosphorus credits from: a. previous phosphorus application; b. manure; c. biosolids and other organic amendments; d. wastewater.

Previous Phosphorus Application Previous phosphorus applications are an important consideration when they have not matched crop removal. Applications at rates in surplus of crop removal tend to increase soil test levels, while rates in deficit of crop removal do the opposite. Soil testing is the recommended method for accurately assessing change in soil test values. To calculate an estimate of current soil test level from one previous (preferably from less than four years past), increase it by 1 ppm for each 25 to 37 kg/ha of phosphate surplus or decrease it by the same amount in the case of phosphorus deficit. This calculation does not impact the phosphorus rate recommended substantially unless the surplus or deficit of the phosphorus balance is large.

Manure Manure credits for phosphorus are determined from an analysis of the manure to be applied, or from tables for the specific type of manure (OMAFRA Publication 811). Values reported as “P” (the elemental form) can be converted to P2O5 (the oxide form) by multiplying by 2.29. In tables or laboratory reports, “available phosphorus” may be reported, and is calculated as 40% of total phosphorus. In the long term, 80% to 100% of the total P in manure contributes to soil test P. Biosolids and Other Organic Amendments Biosolids and other organic amendments are often applied at rates providing more phosphorus than needed for either optimum crop yields, or to replace crop removal. Rates of application may be governed by a NASM plan, based on current soil test P levels (OMAFRA Sewage Biosolids).

Wastewater Wastewater from sources on or off the farm applied to cropland (most often by irrigation) should be analyzed for phosphorus to determine its contribution to crop nutrition and to ensure that excessive amounts are not applied. Several application options exist for greenhouse nutrient feedwater, covered by Ontario Regulation 300/14 (OMAFRA, 2016). See P.O. 1, Proficiency Area 1, Nutrient Management Planning.

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Performance Objective 8 Justify the potential need to adjust the phosphorus application rate based on legacy phosphorus and application method.

The term “legacy phosphorus” refers to that which has accumulated as a result of past human activity.

In cropland, the main source of legacy phosphorus is that which has been applied in the past from fertilizers, manures, biosolids, or other sources, net of crop removal. Soil test phosphorus adequately reflects historical phosphorus accumulation or depletion, so there is no need for separate consideration of legacy phosphorus in the soil. Legacy phosphorus also includes that which has accumulated in stream and river sediments. Managing its impact on water quality may involve protection of stream banks from erosion, but is not affected by the choice of phosphorus application rate.

Application method or “right place” may in some cases influence the amount applied. When phosphorus sources are band-placed in or near the seed row, maximum safe rates should not be exceeded (OMAFRA Publication 611 Table 7-4, or Publication 811, Table 9-21). The maximum safe rate for application of diammonium phosphate is lower than that for other fertilizer sources. For replenishment of crop removal, however, application method requires no adjustment to phosphorus application rate.

Competency Area 3 Determining the Right Timing of Phosphorus Application Performance Objective 9 Discuss the importance of the following on phosphorus application timing: a. intensity of precipitation; b. type of precipitation; c. duration of precipitation; d. runoff.

Precipitation and runoff are risk factors for phosphorus loss in runoff and drainage water mainly when phosphorus sources are broadcast applied and left on the soil surface. Broadcast applications of phosphorus sources should be avoided when substantial rainfall is imminent or forecast to occur before the material can be incorporated into the soil.

Broadcast applications in late summer or early fall (i.e. after wheat or small grain harvest) are less likely to contribute to runoff phosphorus loss than applications in late fall or early spring, because soils are drier and can absorb more rain before generating runoff, and the ratio of precipitation to potential evaporation is smaller. Broadcast application of P on frozen or snow-covered soil in the winter is never the right time, no matter what the source, because runoff risks are very high when rain falls on frozen soil. For band-applied phosphorus, application timing is a consideration only if rain is likely to create channel erosion of the bands.

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Performance Objective 10 Discuss the mechanisms of phosphorus loss to surface water.

Phosphorus is lost in two forms, either particulate or dissolved. Particulate losses occur as a result of soil erosion. In the particulate form, phosphorus is attached to suspended particles of sediment. These particles are usually clay or silt. In cultivated fields, most of the P lost (70% or more) is in the particulate form. Surface runoff from grass, forest, or noncultivated soils, however, carries little sediment and is generally dominated by dissolved P (about 80% of total P loss).

Losses of dissolved phosphorus also occur when sources containing soluble phosphorus are left on the soil surface without mixing with the soil. These sources include commercial fertilizer, manures, biosolids and fresh plant residues.

Performance Objective 11 Discuss reduction strategies and management for particulate phosphorus loss.

The loss of particulate forms is managed by controlling soil erosion, and preventing buildup of soil test P to unreasonably high levels. Soil erosion and soil test P are both accounted for in the Ontario Phosphorus Index (OMAFRA, 2005). An implementation for RUSLE 2.0 has also been made available (OMAFRA, 2014).

Control of soil erosion is managed by choice of crop rotation, cover crops, and tillage strategies. In general, minimal or zero tillage helps reduce soil erosion by increasing soil cover by crop residue.

Contour tillage or tillage across rather than along the slope helps to minimize soil erosion. Timeliness of tillage and other field operations to minimize soil compaction is also important. Maintaining soils in a well-drained condition through use of grassed waterways and tile drains also helps prevent erosion.

Buffers help stabilize stream banks, protecting them from erosion and particulate P loss as well. Control of wind erosion through use of windbreaks can also help prevent transfer of particulate P to rivers and lakes.

Preventing buildup of soil test P is accomplished by applying at rates in accordance with recommendations based on soil testing, ensuring that application rates do not exceed removals when soil test P is at optimum levels, and applying less P than crop removal, or none, on soils with higher soil test P than necessary. Buildup of soil P stratification should also be managed by ensuring sufficient depth of P placement, by either injecting or incorporation.

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Performance Objective 12 Discuss reduction strategies and management for dissolved phosphorus loss.

Losses of dissolved phosphorus are managed by ensuring that any applied nutrient forms containing soluble phosphorus are mixed into the soil before any runoff-generating rainfall, or placed below the soil surface. Both manures and fertilizers contain soluble P, and thus when left on the soil surface, may dissolve into runoff water.

Runoff risks vary seasonally. Generally surface runoff occurs more frequently in late fall and early spring. Any soluble nutrients applied in winter are therefore susceptible to loss in runoff water during spring rains and snowmelt. Surface runoff is much less likely in late summer and early fall (e.g. following harvest of wheat and small grains). Surface broadcast applications are much less likely to increase losses of dissolved P when made in late summer or early fall. For situations where incorporation is not practical, such as perennial forages, P applications that follow first or summer cuts risk less harm to water quality than those made in early spring or late fall.

Cover crops, and careful management of tillage and field operations to prevent soil compaction can help increase infiltration and soil water holding capacity, and reduce the proportion of rainfall received that runs off.

The overall management strategy may include drawdown of soil test P, if soil test P levels are much higher than the agronomic optimum, and field structures to control runoff. These practices are outlined in greater detail in OMAFRA (2011). It may also include drainage water management if it is suited to the farm landscape (see Performance Objective 19 for further detail).

Performance Objective 13 Discuss how phosphorus contamination of surface water can occur from tile drainage due to timing of application.

In many tile-drained fields, macropores created by cracking in clay soils, or by earthworm channels in any soil, cause preferential flow of surface water directly to the tile, with little time for interaction of this water with the soil matrix. Because of the rapid nature of preferential flow, sorption of phosphorus to the surfaces of soil particles is minimal. If phosphorus fertilizer or manure is broadcast on the surface within a few days of a rainstorm large enough to generate macropore flow, this flow path can allow water, highly enriched in dissolved phosphorus, to reach the tile drain. This is an important pathway of loss for the western basin of Lake Erie (Fisher, 2014). Producers are advised to pay close attention to the weather forecast, and avoid broadcasting P fertilizer when there is more than 50% chance of intense rain within the next few days. Levels of dissolved P in runoff decline considerably if a runoff event occurs more than three to five days after application.

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Competency Area 4 Determining the Right Placement/Method of Application for Phosphorus Performance Objective 14 Discuss the importance of the following in determining the optimal placement or method of application of phosphorus: a. intensity of precipitation; b. type of precipitation; c. duration of precipitation; d. runoff.

Precipitation and runoff are risk factors for phosphorus loss in runoff and drainage water mainly when phosphorus sources are broadcast applied and left on the soil surface. When applied phosphorus is placed below the soil surface, or mixed with the bulk soil, risks of dissolved phosphorus loss are minimized (IPNI, 2013). The process of application or soil mixing, however, may disturb the residue cover of the soil and make it more prone to soil erosion. For this reason, on soils prone to soil erosion, risks of intense rainstorms and runoff need to be considered when choosing the combination of placement and timing for phosphorus application.

Performance Objective 15 Discuss the relationship between tillage practices/system on phosphorus management.

In cropping systems where the soils are moldboard plowed every few years, soil test phosphorus levels are fairly uniform within the plow depth. In no-till cropping systems, particularly where phosphorus sources are surface applied, soil test phosphorus levels are stratified, with the top two to three cm of soil around three times as high as the top 15 to 20 cm. When conservation tillage tools are used, soil test P stratification is intermediate between these two extremes (Bruulsema, et al., 2012).

In no-till systems, the soil mycorrhizal network flourishes, providing more phosphorus to the crop for a given soil condition. Soil conditions in no-till, however, are often colder and wetter in the spring than in tilled soils, often resulting in higher crop phosphorus need for early season growth and greater crop response to applied phosphorus. The two considerations often balance each other, so the recommended amounts to apply do not change depending on tillage system.

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Performance Objective 16 Discuss the considerations for phosphorus placement and method of application based on the risk of phosphorus runoff.

Consideration of risks of phosphorus runoff may lead to different choices for placement than when crop response is the only consideration.

In many soils, little difference in crop response is expected between broadcasting on the soil surface as compared to broadcast and incorporated, or band application. Placing phosphorus below the soil surface can dramatically reduce risks of loss in the dissolved form in surface runoff or in tile drainage water (Bruulsema et al., 2012; Culman et al., 2014).

Spatial variability within fields should be managed to prevent accumulation of extremely high soil test levels in parts of the field where either nutrient removals are low, or where historical buildup has occurred from large manure applications or depositions.

Monoammonium Phosphate (MAP). Courtesy Fertilizer Canada

Performance Objective 17 Plan the best placement or application method for phosphorus to minimize the transport of phosphorus offsite.

Selection of the â&#x20AC;&#x153;right placeâ&#x20AC;? requires consideration of the following principles: 1. The choice of right place depends on source, rate and time of application.

2. Phosphorus needs to be available where plant roots are growing.

3. Concentrating phosphorus into enriched zones can improve availability in soils with high phosphorus sorption capacity.

4. Crop residue cover on the soil surface should be managed to control soil erosion.

5. Spatial variability in phosphorus needs should be addressed.

The steps to determining any 4R nutrient stewardship plan are designed to be consistent with the principles of adaptive management. These are described in IPNIâ&#x20AC;&#x2122;s 4R Plant Nutrition Manual, Chapters 7 and 9. The five steps include setting sustainability goals, gathering production information, formulating the plan, implementing the practices, and monitoring the effectiveness of those practices.

1. Setting sustainability goals.

For the whole farm or enterprise, these goals need to consider the interests of stakeholders who may include neighbors, customers, local public interest groups, farm or business associations, or other organizations active in voluntary promotion of sustainability improvement. When farmland is leased, discussions should occur between the land owner and the farmer operator to determine who is responsible for implementing sustainability practices and monitoring their effectiveness. Set PROFICIENCY AREA III - Phosphorus

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economic, environmental and social goals for the enterprise, with performance indicators chosen with consideration of the concerns of the people listed above. For phosphorus, and its placement, important concerns are likely to include cropland productivity, soil fertility, and water quality.

2. Gather needed production information – for each field: a. Crop to be grown, and its target yield and quality (P influences crop maturity as well as yield). b. Soil characteristics including texture, organic matter, pH, levels of available nutrients. c. For decisions on application timing and placement, expected number of days of suitable soil conditions for field operations based on soils and typical weather. d. Water drainage, infiltration rates, potential for macropore flow to tile drains, pathways to surface water, opportunity for buffers and biofilters to reduce loss of particulate P. e. Location, dimensions and surface area (e.g., legal description, GPS coordinates, map). f. Equipment available for applying nutrients; opportunity and potential for applying variable rates of nutrients at a sub-field scale. g. Reliable recommendations and decision support tools.

3. Formulate the Plan - for each field: a. Review soil test P levels, and decide whether to build, maintain or draw down. b. Estimate crop P removal based on target yield. c. Consider the supply of all available nutrients and choose the most feasible nutrient source and the appropriate rate, time and place for its application.

4. Implement the chosen practices.

This can be done by the farm manager or in combination with advisors, fertilizer retailers or custom applicators, buyers, and regulatory staff. Recording and tracking precisely what was done, and how well it fit in with the logistics of field operations and timely crop planting, is an important part of the adaptive management cycle.

5. Monitor the effectiveness of the practices employed.

The final step in the cycle of adaptive management assesses performance through the chosen indicators to determine whether the practices selected achieved the intended results. This assessment then influences the next cycle of planning decisions (i.e., from step 2). The impact of many practices cannot easily be measured within a single growing season and will need to be assessed over multiple years to document improvements.

Monitoring can include: a. timeliness of field operations, particularly crop planting. b. in-season and at-harvest crop nutrient concentrations; c. yields achieved in relation to target; d. calculation of P nutrient balances; e. monitoring of water quantity and quality leaving the farm at drainage outlets (not economically feasible for P losses for most farms); f. measuring or assessing soil P fertility and soil health using appropriate indicators.

Establishing buffers, grassed waterways and biofilters can be effective practices for keeping particulate P in the “right place” (out of drainage water leaving the field). Excluding livestock from streams can also be considered a “right place” practice, since it keeps the manure from grazing cattle from being directly deposited in the stream (OMAFRA, 2011; Zeckoski et al., 2012).

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Performance Objective 18 Discuss how phosphorus contamination of surface water can occur from tile drainage due to placement and method of application.

Phosphorus sources left on the soil surface have the first interaction with water from any rainstorm. If the rainstorm is large enough to generate flow through macropores to the tile drains, this interaction results in water with relatively high concentration of dissolved phosphorus moving out of the fields through tile drains to contaminate surface water in ditches, streams and rivers. Placing phosphorus on the surface of tile drained soils with macropores constitutes an acute risk for delivery of dissolved phosphorus to drainage water, elevating concentrations of phosphorus in stream water and harming water quality in streams, rivers, and lakes. For phosphorus sources applied with a large volume of water, e.g. liquid manure, the risk is particularly acute, and can be managed by tilling the soil directly over the tile drains prior to liquid manure application.

Conservation tillage seeks to maintain residue cover and control soil erosion, limiting loss of particulate forms of phosphorus. When tillage is reduced or eliminated, available forms of phosphorus tend to accumulate in the uppermost few centimeters of soil, particularly if the main phosphorus application method is broadcasting without incorporation. Such stratification of available soil phosphorus is a chronic risk to water quality, and can be measured by soil testing and comparing the top few centimeters to the typical 15 to 20 centimeter sampling depth.

To manage both the acute and chronic risks in soils with tile drainage and macropore flow, it is necessary to get the phosphorus incorporated into the soil in some way (Fisher, 2014). Injection without tillage may be possible, particularly for fluid forms of fertilizer. Other possibilities include strip tillage with injection of fertilizer or manure, or light tillage after broadcasting that leaves sufficient crop residue cover to control soil erosion. In cases of high soil phosphorus stratification, where soil erosion risks are low, occasional (e.g., once in 10 or more years) inversion tillage with a moldboard plow may reduce phosphorus losses to water.

Performance Objective 19 Discuss how to use drainage water management to reduce phosphorus nutrient losses to surface water.

Drainage water management involves controlling the level of the soil water table at specific times of year, as opposed to allowing free drainage through the tiles. Since the total flow of water is reduced, the total phosphorus load from the field may be decreased. The concentration of phosphorus in the water, however, may also be influenced. It may either increase or decrease as a result of changes in the oxidation state of the soil. Release of phosphate from iron phosphate complexes often occurs in more reduced conditions. There is also more time for the water to interact with subsoil, which can in some instances reduce the concentration of dissolved phosphorus.

When drainage water management is combined with subirrigation, by capturing drainage water in a retention pond for use later in the summer by pumping it back, phosphorus losses can be reduced dramatically. Adequate space for a retention pond is a major limitation for subirrigation, however.

Research in controlled drainage with subirrigation was shown to reduce particulate phosphorus loss by 10% (Frey, Hwang, Park et. al, 2016) to 15% (Tan and Zhang, 2011) in Ontario, relative to regular free drainage. Drainage water management generally works best on flat fields with minimal slopes.

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Competency Area 5 Environmental Risk Analysis for Phosphorus Performance Objective 20 Discuss how to use water quality vulnerability assessment tools (e.g. Source Water Protection Plans) on a site specific basis for phosphorus nutrient planning.

The Ontario Ministry of the Environment and Climate Change has approved 22 source water protection plans within the province (MOECC, 2016). Any field falling within a risk management zone of a source water protection plan must follow the specifications of that plan. Most plans do not address phosphorus specifically, but in certain zones deemed vulnerable there may be restrictions affecting animal penning, manure storage or fertilizer use. In addition, the use of nutrient management plans may be required or encouraged (Conservation Ontario, 2013).

Performance Objective 21 Evaluate phosphorus management decisions using a water quality vulnerability assessment (e.g. Phosphorus Index).

The Ontario Phosphorus Index requires input data for the following: 1. Universal Soil Loss Equation (USLE) rating for the field. A = R x K x LS x C x P (OMAFRA, 2012) • A represents the potential long-term average annual soil loss in tonnes per hectare (tons per acre) per year.

• R is the rainfall and runoff factor by geographic location. The greater the intensity and duration of the rain storm, the higher the erosion potential.

• K is the soil erodibility factor. It is a measure of the susceptibility of soil particles to detachment and transport by rainfall and runoff. Texture is the principal factor affecting K, but structure, organic matter and permeability also contribute.

• LS is the slope length-gradient factor. The steeper and longer the slope, the higher the risk for erosion.

• C is the crop/vegetation and management factor. It is used to determine the relative effectiveness of soil and crop management systems in terms of preventing soil loss.

• P is the support practice factor. It reflects the effects of practices that will reduce the amount and rate of the water runoff and thus reduce the amount of erosion. The most commonly used supporting cropland practices are cross-slope cultivation, contour farming and strip cropping.

2. Water Runoff Class a. Soil hydrological group b. Maximum field slope within 150 m of top of bank of surface water 3. Soil test phosphorus.

4. Commercial fertilizer application rate and method.

5. Manure/biosolid application rate and method.

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The P Index can impact a nutrient management plan in two separate ways: â&#x20AC;˘ sets minimum separation distances for nutrient application close to surface water, and â&#x20AC;˘ determines maximum phosphorus application rates in vicinity of surface water.

The following table recommends management actions according to the P Index value.

Table 3.1. Phosphorus Application Rates and Setback Distances for P Index Ranges Phosphorus Index for Site

Generalized Interpretation of Phosphorus Index for Site

Minimum Setback1 from Surface Water if P2O5 is applied up to crop removal2 [ft (m)]

Minimum Setback from Surface Water if P2O5 is applied over crop removal [ft (m)]

< 15

Very low potential for P movement from the site. If farming practices are maintained at the current level there is a small chance that P losses from this site will have an adverse impact on surface waters.

10 (3)

100 (30)

15 - 29

Low potential for P movement from the site.

The chance for an adverse impact to surface water exists. Some remedial action should be taken to lessen the potential for P loss if application is close to surface water.

10 (3)

100 (30)

30 - 50

Moderate potential for P movement from the site and for an adverse impact on surface waters to occur unless remedial action is taken. In areas close to surface water, soil and water conservation along with P management practices are needed in order to reduce the risk of P movement and water quality degradation.

10 (3)

200 (60)

> 50

High potential for P movement from site and for an adverse impact on surface waters.

Remedial action is required to reduce the risk of P movement. All necessary soil and water conservation practices plus a P management plan must be put in place to avoid the potential for water quality degradation.

100 (30)

Do not apply over crop removal

1. With manure application, it is recommended that the minimum separation distance be met in order to address direct surface runoff concerns. See Section Q, Table 15: Minimum Separation Distance (with established buffer zone) in OMAFRA Publication 818, Nutrient Management Workbook, for more details.

2. The maximum allowable application rate is recommended to be the lowest rate calculated in the Table in Section S - Maximum Rates, OMAFRA Publication 818, Nutrient Management Workbook.

Chart source: OMAFRA 2005, Determining the Phosphorus Index for a Field Factsheet, Agdex #531/743.

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Performance Objective 22 Be able to evaluate how changing a specific phosphorus management strategy will affect the outcome of a risk assessment.

A phosphorus management strategy includes source, rate, time and place of phosphorus application, interacting with tillage and crop rotation choices and conservation practices and structures deployed at edge of field to intercept runoff water. All of these strategy components are reflected in risk assessment tools that are generally available from state or provincial agricultural extension and soil conservation agencies. In Ontario, the recognized risk assessment tool is the Ontario Phosphorus Index (OMAFRA, 2011).

As described in Performance Objective 21, there are numerous management practices that affect the outcome of the assessment conducted with the Ontario Phosphorus Index.

Table 3.2. Effect of Best Management Practices (BMPs) on P Index (adapted from OMAFRA, 2005).

Site Characteristic Soil Erosion

Water Runoff Class

Management Practices that will Lower P Index Any practice to reduce soil erosion.

Example of BMPs Reduce slope length; tillage to increase surface residue; plant cover crops; crop rotation, strip cropping, contour tillage.

Tile drains may reduce runoff water volumes and thus lower risk of P loss in surface runoff. They also In some instances, tile drainage installation may increase risk of P loss through tile drains by increasing change the effective soil hydrologic group rating. connectivity. A new version of the P Index, in preparation, may address these factors more explicitly.

The management of fertilizer and manure Phosphorus Soil Test application methods/rates will control the rate at which the phosphorus level in the soil changes.

The phosphorus level of a field can be lowered on a long-term basis by reducing or eliminating application rates of manure/fertilizer and/or using crops with higher P removal capabilities.

Commercial Fertilizer Applying less fertilizer to a field will lower the Application Rate level of phosphorus accordingly.

A reduction in the commercial fertilizer application rate from 60 lbs P2O5/acre to 30 lbs P2O5/acre will reduce the P Index by 1 point.

The use of an application method that Commercial Fertilizer incorporates the fertilizer quickly and efficiently Application Method will result in a lower rating factor.

By changing the application method from non-incorporated to placed with planter, the P Index is reduced by 10.5 points.

Manure /Biosolid Application Rate Manure /Biosolid Application Method

96

Applying less manure to a field will lower the level of phosphorus accordingly.

A reduction in the manure/biosolid application rate from 60 lbs P2O5/acre to 30 lbs P2O5/acre will reduce the P Index by 3 points.

The use of an application method that incorporates the manure quickly and efficiently will result in a lower rating factor.

Changing the application method from non-incorporated on bare soil to injected will cause the P Index to be reduced by 10.5 points.

PROFICIENCY AREA III - Phosphorus

Performance Objective 23 Evaluate management strategies, including modifying phosphorus transport processes, which will reduce phosphorus loss to surface water and groundwater.

Tile drainage can increase or decrease phosphorus loss from farm fields. It can reduce soil erosion, because drained soils are less frequently saturated with water, and saturated soils generate more runoff from a rainfall of a given size. Since tile drains provide a quicker connection for transport of water, however, it can increase the transport of phosphorus from the soil surface to the edge of field.

Management strategies to control phosphorus loss need to account for the transport pathways.

Grassed field borders and grassed waterways can slow down runoff and remove some of the sediment and soil-attached phosphorus at the edges of fields. They also help stabilize stream banks, preventing transport of particulate P from bank scour. They are less effective, however, in controlling the transport of dissolved phosphorus.

Diversion terraces, constructed across slopes, reduce erosion and runoff by intercepting, detaining and safely conveying runoff to an outlet.

Water and sediment control basins (WASCoBs) are commonly installed to prevent bank and gully erosion on farmland. Ponded water is slowly released to an underground drainpipe, either through a riser pipe or a blind inlet constructed by filling in the bottom of the ponded area with sand and gravel.

Buffer strips planted to permanent vegetation such as grass, shrubs, trees or some combination of these can help stabilize stream banks, prevent gullies from forming, and filter out some sediment-bound phosphorus. They also help absorb nitrate, and provide wildlife habitat.

Cover crops can protect the soil surface from erosion. They are effective in reducing loss of sediment bound P, but not very effective in reducing loss of dissolved P. Furrow management and contour cultivation can help minimize soil erosion and surface runoff.

Wetlands can trap particulate P until they fill with sediment. They have low efficacy in removing dissolved P.

Performance Objective 24 Discuss how tillage system (including no-till) affects environmental losses of phosphorus.

Tillage influences soil erosion and is accounted for in the Universal Soil Loss Equation component of the Ontario Phosphorus Index. Avoidance of tillage or conservation tillage, however, results in some degree of soil phosphorus stratification, with higher levels accumulating in the top few centimeters of soil. This stratification effect is not accounted for in the Phosphorus Index. The concentration of soluble phosphorus in runoff water, or in water moving to tile drains by macropore flow, is influenced by the soil test phosphorus level in the top few centimeters of soil. For this reason, conservation tillage combined with surface applications of phosphorus may increase losses of soluble phosphorus while decreasing losses of the particulate form.

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Performance Objective 25 Compare the differences in the geographic scale, soil, topography, and location of watersheds (e.g. national, regional, local) on the environmental impacts of phosphorus on surface and groundwater resources.

Scale Phosphorus losses may affect water quality in local streams, ponds, and reservoirs as well as in larger rivers and lakes. Abundant algal growth can make the water in some of these water bodies unpleasing or unsuitable for drinking or swimming, and the deposition of dead algal biomass can deplete bottom waters of oxygen, limiting growth of fish and other aquatic animals.

Soil Soils of finer texture are generally more prone to runoff and thus losses of phosphorus. Sandier soils tend to lose less phosphorus, even when tile drained, since water flow to tiles is primarily by matrix flow. One exception would be sandy soils with soil test P built up to extremely high levels; such soils may transfer dissolved phosphorus to streams either through tile drains or by lateral flow of the groundwater, where water tables are found at a shallow soil depth.

Topography Soils with steeper and longer slopes are more prone to both surface runoff and soil erosion. Control of soil erosion on such soils may be more important than control of losses of dissolved phosphorus.

Location of Watershed Climate is an important controller of runoff. Seasonal charts comparing precipitation to potential evapotranspiration can help guide decisions on application timing for fertilizers, manures and other materials containing phosphorus. In Ontario, runoff risks in fall versus spring do not differ as much as in the Western Corn Belt (e.g. Iowa) where runoff risks are generally lower in the fall than in the spring.

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Performance Objective 26 Discuss the role of phosphorus, including legacy phosphorus, in the eutrophication process and the potential consequences of eutrophication.

Phosphorus in aquatic systems can accelerate freshwater eutrophication. Eutrophication is one of the most common impairments of water quality in North America. Eutrophication restricts water use for fisheries, recreation, and industry due to the increased growth of undesirable algae and aquatic weeds, and oxygen shortages caused by their death and decomposition. Also, an increasing number of surface waters have experienced periodic and massive harmful algal blooms (for example, cyanobacteria), which contribute to summer fish kills, and may restrict water use for public drinking water supplies (Sharpley et al., 2006).

Legacy phosphorus refers to the accumulation of phosphorus in land or in aquatic systems that is the result of past human activities, including management of both nutrients and land. It includes the buildup of phosphorus in agricultural soils, to levels either optimal for or in excess of crop requirements, and modifications of the transport pathways from land into streams, rivers and lakes. High levels of phosphorus built up in the soil from past nutrient applications can result in elevated P losses from these fields for many decades after P applications cease, delaying improvements in water quality.

Within rivers and lakes, a range of processes control the retention and release of phosphorus from accumulated sediment, with resulting influences on eutrophication (Sharpley et al., 2013).

Permanently vegetated buffer protecting the banks of the Credit River.

Courtesy Credit Valley Conservation

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PROFICIENCY AREA IV

POTASSIUM, SECONDARY MACRONUTRIENTS AND MICRONUTRIENTS Competency Area 1 Determining the Right Source of Potassium, Secondary Macronutrients and Micronutrients Performance Objective 1 Discuss the most common sources of potassium, secondary macronutrients and micronutrients used in Ontario.

There are numerous products that contain potassium. The predominant products available for purchase in Ontario are muriate of potash, sulphate of potash, sulphate of potash magnesia and potassium nitrate. There are many more liquid mixed products that are commercially available as blends that contain potash. These are mainly used as starter or pop-up fertilizers on the seed or as prescribed by the manufacturer. Most livestock manure contains significant concentrations of potassium, and can provide most or all of the potassium requirements for crops on land receiving manure.

Table 4.1. Granular Fertilizer Ingredients Grade1 (%)

Other nutrients2

Salt index3

CaCO3 equivalent4

Bulk density5

Relative cost/ unit nutrient6

lb/lb

lb/cu ft

kg/L

70

-1.9 (B)

75

1.20

2.54

Potassium nitrate

12-0-44

Muriate of potash (red)

0-0-60

45% Cl

115

neutral

70

1.10

1.00

Muriate of potash (white)

0-0-62

46% Cl

116

neutral

75

1.20

1.00

Potassium sulphate

0-0-50

18% S

42.6

neutral

75

1.20

2.34

Sulphate of potash-magnesia

0-0-22

20% S 11% Mg

43.4

neutral

94

1.50

3.71

1. Grade: guaranteed minimum percentage by weight of total N, available phosphoric acid (P2O5) and soluble potash (K2O) in each fertilizer material.

2. Other nutrients nutrients other than N, P or K. 3. S alt index: comparison of relative solubilities of fertilizer compounds with sodium nitrate (100) per weight of material. When applied too close to the seed or on the foliage the higher salt index materials are more likely to cause injury.

4. CaCO3 equivalent: pounds of lime required to neutralize the acid formed by one pound of the N supplied by the fertilizer material. â&#x20AC;&#x153;Bâ&#x20AC;? following the lime index indicates a basic (acid-neutralizing or alkaline) ingredient. Note: acid-forming effects can be up to twice as great as indicated, depending on plant uptake processes.

5. Bulk density: expressed as pounds per cubic foot or kg/L, important since fertilizers are metered by volume rather than weight in spreaders or planting equipment.

6. Relative cost/unit: based on 1998 prices of urea for N, triple superphosphate for P and muriate of potash for K. Source: Soil Fertility Handbook, Publication 611, OMAFRA, 2006, p. 152.

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Table 4.2. Liquid Fertilizers Analyses

Weight/ US gal (lb)

Weight/ Imp. gal (lb)

Weight/ litre (lb)

Imp. gal/ tonne

US gal/ tonne

Litre/ tonne

8-25-3

11.11

13.35

2.94

165.1

198.4

749.9

6-18-6

10.69

12.85

2.83

171.6

206.2

779.0

3-11-11

10.45

12.55

2.76

175.7

211.0

798.8

9-9-9

10.49

12.60

2.77

175.0

210.2

795.9

7-7-7

10.41

12.5

2.75

176.4

211.8

801.7

6-24-6

11.07

13.30

2.93

165.8

199.2

752.4

9-18-9

11.07

13.30

2.92

165.8

199.2

755

5-10-15

10.7

12.85

2.83

171.6

206.0

799

2-10-15

10.62

12.75

2.81

172.9

207.6

784.6

10-34-0

11.6

14.0

3.09

157.0

188.5

715.8

UAN (28% to 32%)

10.65

12.8

2.82

172.2

207.0

781.8

Aqua ammonia 20-0-0

7.49

9

1.98

245

294.3

1113.4

54% phos. acid

13.15

15.8

3.48

139.5

167.7

633.5

1 Imperial gallon = 1.201 US gallons 1 US gallon = 3.785 litres

1 US gallon = 0.8326 Imperial gallons 1 Imperial gallon = 4.546 litres

Source: Adapted from Table 7-2 Blended liquid fertilizers, Soil Fertility Handbook, Publication 611, OMAFRA, 2006, p. 156.

Potassium (K) sources Muriate of potash (0-0-60 or 0-0-62) • KCl potassium chloride • most common and least expensive source of K • contains chlorine (47%), an essential plant nutrient needed for cell division, photosynthesis and disease suppression, in the chloride form • a small amount (less than 100 grams per tonne) Muriate of Potash (red). Courtesy Fertilizer Canada of an amine/oil anti-caking agent is often included in the shipped product • the availability of the K to plants is equal from red and white forms.

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Red muriate of potash (0-0-60) • mined primarily in Saskatchewan and some in New Brunswick • contains about 97% potassium chloride (KCl), balance is mostly iron impurities which are responsible for the colour

White muriate of potash (0-0-62) • obtained by crystallizing potassium chloride out of the mining liquor solution • almost pure potassium chloride Potassium sulphate (0-0-50) • K2SO4 • extracted from the brines of Great Salt Lake in Utah • also contains 17% sulphur in the water soluble form Potassium sulphate, or sulphate of potash, has a lower salt index and is more expensive than muriate of potash. It is used mainly on crops sensitive to chloride, such as tobacco, potatoes, tree fruits and some vegetables, or where sulphur is required for the crop.

Sulphate of potash-magnesia (0-0-22) • potassium-magnesium sulphate K2SO4•2MgSO4 • mined from deposits in New Mexico • commonly referred to as K-Mag (brand name of Mosiac Fertilizers’ product) and Sul-Po-Mag Potassium-magnesium sulphate, or sulphate of potash-magnesia, has a higher cost per unit of K than the muriate form. It also contains 11% magnesium and 22% sulphur in water soluble form and therefore readily available to plants. It is useful as a source of soluble magnesium in fields where lime is not required.

Potassium nitrate (12-0-44) • KNO3 • produced commercially by reacting sodium nitrate with potassium chloride • higher cost per unit of K than other sources, so generally used only for specialty fertilizers where soluble forms of both K and N are required Livestock manure • K concentration in manure varies widely, typically ranges from 2.5% to 4.5% of dry matter, depending on livestock species and storage system • Most of the K in manure is soluble and plant available

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Secondary Macronutrients Secondary nutrients are needed occasionally in Ontario soils. If required, they may be applied as part of a fertilizer blend or added as part of a lime application to correct soil acidity.

The secondary macronutrients include: magnesium, calcium, and sulphur. As indicated in Table 4.3, these nutrients can also be supplied in some of the commonly available fertilizer materials. For example, sulphate of potash magnesia contains both magnesium and sulphur. Sulphate of potash contains sulphur as well. Calcium ammonium nitrate can contain small amounts of magnesium along with calcium. Calcium nitrate is an excellent source of N for speciality crops and contains soluble calcium. Gypsum (calcium sulphate) provides both calcium and sulphur.

The requirements for calcium and magnesium are most often associated with acidic soil conditions and the need to correct for proper pH. The two main products used are calcitic or dolomitic limestone.

Calcium Limestone (either calcitic or dolomitic) is the most common source of calcium. It also increases the pH of acidic soils. To be effective, it must be finely ground and thoroughly incorporated into the root zone.

Limestone is available in powder form or in pellets made from finely ground limestone. The solubility of limestone drops quickly as soil pH increases.

In soils with neutral or alkaline pH, gypsum (calcium sulfate) is the preferred form of calcium because it is more soluble than lime. Gypsum has no effect on soil pH. Calcium chloride and calcium nitrate are occasionally used as foliar or soil applied sources of calcium.

However, Ca is not translocated within the plant, so foliar application is only effective for deficiencies in parts of the plant the spray can reach.

Magnesium Magnesium deficiency is most common in acidic soils. If dolomitic limestone is added to correct the acidity, it will also supply enough magnesium to correct the deficiency. The solubility of dolomitic limestone decreases as the soil pH increases, thus it is not effective when applied to alkaline soils. In neutral or alkaline soils, Epsom salts (magnesium sulphate) or sulphate of potash magnesia can be used for supplemental magnesium.

Sulphur Sulphate sulphur is present in a number of common fertilizer materials and can be included in a fertilizer blend. Most common are ammonium sulphate, potassium sulphate, and sulphate of potash magnesia. Gypsum (calcium sulphate) can also be used as a sulphur source. Product availability, transportation costs and crop requirements for other nutrients will dictate which source of sulphur is most economical.

Granular elemental sulphur (90% S) can be another source. It will also acidify the soil. The sulphur must be oxidized to sulphate before it is available to the crop, which can take several months. Some of the intermediate products in the oxidation process can be toxic to crops; therefore, high rates should be broadcast rather than banded. Broadcasting increases soil contact and hastens conversion to the sulphate form. After the initial year of application, the pool of plant available sulphate S will most likely increase.

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Micronutrients The main micronutrients of concern to Ontario agriculture are zinc, manganese and boron. On occasion, copper and molybdenum may be required. There are many forms of commercially available micronutrient products (almost too many to mention), so the choice of product will depend on price, solubility of the nutrient, and suitability of the product for available application systems. Table 4.3 lists some of the common materials available.

Table 4.3. Common Secondary and Micronutrient Sources Nutrient

Calcium (Ca)

Magnesium (Mg)

Sulphur (S)

Source

%

Other

Nutrient

Nutrients

calcitic limestone dolomitic limestone gypsum (CaSO4) calcium chloride (CaCl2) calcium nitrate (Ca(NO3)2) pelletized lime cement kiln dust

22%–40% 16%–22% 29% 36% 19%

6%–13% Mg 23% S 64% Cl 15.5% N

26%–32%

2%–9% K2O

* * * * * * *

dolomitic limestone Epsom salts (MgSO4) sulphate of potash magnesia

6%–13% 9% 11%

16%–22% Ca 13% S 22% K2O; 20% S

* * *

24% 18% 22% 23% 90%

34% N 50% K2O 22% K2O; 11% Mg 29% Ca

* * * * *

ammonium sulphate potassium sulphate sulphate of potash magnesia calcium sulphate granular sulphur

Application Soil

Foliar

* *

*

various granular materials Solubor™

12%–15% 20%

*

copper sulphate copper chelates

25% 5%–13%

*

Manganese (Mn)

manganese sulphate manganese chelates

28%–32% 5%–12%

* *

Molybdenum (Mo)

sodium molybdate

39%

*

Boron (B) Copper (Cu)

Zinc (Zn)

zinc sulphate zinc oxysulphate zinc chelates

36% 8%–36% 9%–14%

*

* *

* *

Source: Soil Fertility Handbook, Publication 611, OMAFRA, 2006, p. 158.

Granular micronutrients These products are blended with other fertilizer ingredients for broadcast application or used as a starter fertilizer. Compatibility with the other ingredients is important, both chemically and in granule size. Since certain micronutrients are toxic to plants if over-applied, segregation of the fertilizer blends must be avoided.

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Oxy-sulphates • combinations of the oxide and sulphate forms of the micronutrient • sulphates much more soluble and available than the oxides • oxides much more stable in a blended product • oxides only slowly available to the crop These products have been declining in popularity because of the inconsistency in plant availability and crop response.

DDP- Dry Dispersible Powders These are finely ground oxy-sulphate materials that are intended to be added to dry blended fertilizer.

The static charge causes these nutrients to cling to each and every granule in the blend with the idea that micronutrients are better distributed throughout the blend and subsequent application enhancing nutrient uptake.

Sulphates • more soluble than oxides • tend to be hygroscopic and can cause problems with caking or clumping when mixed with other fertilizer ingredients. This can be managed by applying the fertilizer soon after blending.

Despite these concerns, their consistent plant availability has made them popular in fertilizer blends.

Liquid and soluble micronutrients These materials may be mixed with water and sprayed on crop foliage or mixed with liquid fertilizers.

Chelates • complex organic molecules that bind metallic ions, protecting them from reactions with other minerals to form insoluble compounds • allows many of these nutrients to be mixed with liquid fertilizers without forming insoluble precipitates • may increase the availability of the nutrients in soil • most commonly used chelating agents are EDTA and DTPA • other organic materials (humic acids, lignosulphonates, glucoheptonates) will form complexes with metallic ions but do not hold them as tightly as a true chelate Chelates are considerably more expensive than other soluble forms of micronutrients. They should be used with care, since they can complex minerals already in the soil and make the deficiency worse.

Soluble powders • least expensive form of micronutrients for foliar application and the most consistently reliable • most require a sprayer with good agitation to keep material in solution • sticker-spreader needed to get the nutrient through the cuticle and into the leaf.

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Performance Objective 2 Discuss considerations that may be used to determine the right source of potassium, secondary macronutrients, and micronutrients based on: a. crop type; b. cropping system; c. crop growth stage; d. soil test or tissue test; e. timing of application.

Choosing the Right Source of Potassium based on Crop Type The four main product choices are muriate of potash, sulphate of potash, sulphate of potash magnesia, and potassium nitrate. All the potassium sources are essentially equal in K availability, so the choices come down to crop safety for particular application methods (that may vary with crop species), other nutrients in the fertilizer with the K, and absence of Cl for specific sensitive crops (e.g. tobacco, raspberries).

Muriate of Potash (MOP) Muriate of potash is used on a broad range of crops and is by far the most common choice. It is readily soluble and plant available. It does contain chloride which can add to the salt index and cause crop damage early in the season if placed too close to the seed and at high rates. Similar considerations apply when contemplating its use on soybeans and wheat and during the establishment year of forages.

Sulphate of Potash Magnesia (SPM) This may be a good choice if the soil pH is in the proper range and there is a clear need for both supplemental sulphur and magnesium.

Red Muriate of Potash. Courtesy Fertilizer Canada

Sulphate of Potash (SOP) This product is considered a low salt index product. If there is a need for sulphur and no other sources of sulphur are coming from other materials then this may be a good choice. However, it is the most expensive form of potassium. Another consideration is for crops sensitive to chloride such as tobacco.

Then, muriate of potash has limited application and SOP is substituted for part of the potassium requirement.

Potassium Nitrate This product is soluble enough to be fertigated throughout the season and provide supplement N and K at critical crop developmental stages. It may be an appropriate choice in vegetable production or where drip irrigation is implemented.

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Livestock Manure Manure is an excellent source of potassium. Potassium content varies by livestock class. A manure lab test or use of book values will be necessary to assess nutrient content and determine rates of application. The K content of manure is highly available in the year of application, it is estimated to be 90%. Manure also contains other nutrients and therefore consideration of other nutrients contained in the manure such as nitrogen and phosphorus may limit the application rate. Various crops in the rotation may have a high demand for K but a low demand for nitrogen thereby limiting application rates. Soils test may be high in P and require no further supplementation of P which may limit manure as a viable source to supply all the required K. Manure is also a good source of micronutrients. Soils that receive regular manure applications are seldom deficient in micronutrients.

Choosing the Right Source of Potassium based on the Cropping System The cropping systems in Ontario are varied. Corn, soybean and wheat rotations both in conventional till and no-till are common cash crop scenarios. Forages, small grains, silage corn and pastures are common amongst livestock producers. Vegetable and specialty crops is another distinct system.

The choice of product depends on the need for supplemental potassium. Muriate of potash is the most flexible and economical in a number of cropping rotations. It can be fall or spring applied, banded (within limits), broadcast or blended with other fertilizers.

Manures may be a viable option if soil tests for P and K indicate that they are required and nitrogen recommendations are not exceeded by the determined application rate.

Crop rotations that include forages and corn silage with high crop nutrient removal are likely the acres to benefit the most from manure applications.

If tobacco is in the rotation, reducing the use of MOP and increasing the use of SOP or SPM will improve quality.

Choosing the Right Source of Potassium based on the Crop Growth Stage In most crop rotations, it is the vegetative growth stage that requires the most potassium. Applying the potassium ahead of time to the soil will insure adequate supply for root uptake. Depending on a foliar application to provide sufficient K is not a good strategy. None of the potassium products can be applied safely and with sufficient quantity to meet the crop demands without causing crop damage.

On soils testing low in K, placing a small amount of K in a starter band on corn has shown significant yield advantage over broadcast K only.

Applying manure in crop has drawbacks both in terms of specialized equipment and practicality of performing the task. Therefore, early pre-plant spring applications that capture most of the available N can be a significant source to supply nitrogen, phosphorus and potassium. Fall applied manure results in lower N availability for the following year but can be a significant source of K to the following crops along with P and micronutrients.

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Choosing the Right Source of Potassium based on the Soil Test or Tissue K Soil testing should always be used to determine the need for supplemental potassium. However, the soil test does not specify the source of K to use. The source should be based on availability of supply, crop quality needs and economics. In most cases, MOP can be used. With some speciality crops such as tobacco a mix of MOP, SOP and sulphate of potash magnesia may be required to reduce the chloride content and/or supply magnesium or sulphur. If high rates of K (>200 kg K2O/ha, or >250 kg N + K2O/ha) are required for spring application on sand soils, SOP may provide greater crop safety, either on its own or as a replacement for part of the MOP. Manure that is either fall or spring applied can offer significant amounts of N, P and K. Manure is a bundle of nutrients therefore the application rate should be considered relative to the particular nutrient needs of the crop and the nutrient content of the manure. This approach will avoid over application of nutrients and offer greater insight in perhaps using manure more effectively in lower testing soils that require more P and K. Plant tissue K will indicate whether the plant K content is above or below a critical level. If the test is below the critical level, then crop growth and yield may be reduced by the lower K concentration.

Seldom is it economical to apply foliar K. There may be an opportunity, if caught early enough, to supply supplemental K to the soil, however, this is rarely practical. Usually, low K is symptomatic of something else limiting K uptake such as dry soil or soil compaction limiting root growth and diffusion rates or surface stratification of K due to shallow incorporation.

Choosing the Right Source of Potassium based on the Timing of Application The timing of K application takes into account crop needs, application equipment options and tillage practices. In the 4R stewardship approach, all the Rs are interconnected. It is difficult to talk about source without including timing, rate and place.

MOP is flexible in so far as it can be banded, broadcast and incorporated in fall or spring. The most important part is to soil test to determine the need, crop quality considerations and apply the appropriate amount to optimize crop performance. K has limited mobility and therefore requires the K to be applied ahead of crop needs and incorporated into the root zone by tillage or equipment that can place it in the root zone.

Small amounts placed in a band as a starter in low K test soils has proven to be a viable option for applying some of the K at planting time. The balance can be broadcast and incorporated in either the fall or spring on the appropriate soil texture.

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Choosing Sources of Secondary and Micronutrients Magnesium The first consideration is to determine the soil pH. If lime is required, the choice of dolomitic limestone will provide a source of magnesium. If pH adjustments are not needed, then a product such as sulphate of potash magnesia would be a choice especially if sulphur and potash are also required. If it is determined that only magnesium is required, there are numerous sources of magnesium sulphate or magnesium oxy sulphate from which to choose.

Calcium The choice of calcium follows the same logic as dolomitic limestone. If pH adjustments are needed and magnesium levels are greater than 100 ppm, then choose either calcitic or dolomitic limestone. It is rare for a soil to have inadequate calcium if the pH is in the agronomic range. If supplemental calcium is needed, choose products such as gypsum if sulphur is also required or calcium nitrate if it is also appropriate to add nitrogen.

Sulphur The plant available form of sulphur is sulphate. For in-season applications, it is important to choose products that contain sulphate sulphur. There are numerous products as previously mentioned. If nitrogen is also required, ammonium sulphate is a good source. Use of elemental sulphur requires it to be converted to sulphate forms by soil bacteria. As such, it is not considered a readily available form of sulphur for plants until it converts to sulphate form which could take weeks to several months to convert.

Farms with a history of manure applications may have sufficient levels of plant available sulphate sulphur.

Zinc The most plant available forms of dry zinc are those that contain a significant portion of sulphate.

The least available are zinc oxides. Farms with a history of manure may also have elevated levels of micronutrients, the organic chelates in manure as well as significant levels of zinc contained in most manure will maintain soil test levels.

Manganese As with zinc, the most plant available forms of dry manganese are those that contain a significant portion of sulphate. The least available are manganese oxides. Soil applications are best done in banded starter fertilizers rather than broadcast. However, soil applied manganese is the least effective way to supply manganese. Foliar applications will give more consistent responses for correcting Mn deficiency because they avoid soil reactions that reduce availability.

Boron Numerous boron formulations in both dry and liquid are commercially available. Boron can be toxic to plants if over applied, care is required not to exceed recommended rates.

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Choosing the Right Source of Calcium, Magnesium and Sulphur based on the Crop Type With few exceptions, the choice of products for calcium and magnesium is done by determining the need for limestone applications using pH and BpH determinations. Most of our agronomically important crops require soil pH near neutral or slightly below for optimum performance. An exception is potatoes which, due to disease control reasons, prefer lower pH for scab control but may require higher calcium levels for quality. Gypsum is an option here to supply calcium but not influence soil pH. Sulphur needs are increasing because environmental regulations have reduced industrial sulphur emissions, and therefore reduced wet deposition on agricultural areas. Winter wheat, canola and alfalfa are three crops that are most likely to respond to supplemental sulphur, although responses have not been consistent. The most appropriate sources of sulphur, for the current yearâ&#x20AC;&#x2122;s growth, are those that provide sulphate sulphur. Elemental S may be utilized for longer-term applications. After the initial year of elemental S application the pool of plant available sulphate in the soil will most likely increase.

Choosing the Right Source of Calcium, Magnesium and Sulphur based on the Cropping System In a crop rotation, the choice of calcium and magnesium is often dependent upon the soil pH. It is the most sensitive crop in the rotation that determines the pH required for optimum growth and therefore the need for limestone. The choice of calcitic or dolomitic is based on the need for magnesium.

If the pH is in the correct range, then the need for supplemental magnesium, calcium or sulphur would require the use of products other than limestone. Products such as sulphate of potash magnesia would be a choice especially if sulphur and potassium are also required. If it is determined that only magnesium is required, there are numerous sources of magnesium sulphate or magnesium oxy-sulphate materials to choose from. If calcium is required, then gypsum is an obvious choice.

Crops in the rotation, mainly wheat or alfalfa, will dictate the need for plant available sulphate sulphur.

Choosing products that only supply sulphate is difficult. Choose products that supply other nutrients that are also required. For example, ammonium sulphate supplies both plant available sulphur and nitrogen, and so is appropriate for application on wheat, but potassium sulphate may be more appropriate for application on alfalfa. Blending products (e.g. ammonium sulphate and urea) can provide the needed nutrients at appropriate rates for the lowest cost.

Choosing the Right Source of Calcium Magnesium and Sulphur based on the Crop Growth Stage Calcium, magnesium and sulphur are taken up all season long by most crops. An adequate soil supply is required. To assure an adequate supply requires adjusting soil pH with either calcitic or dolomitic limestone the year ahead to give time for reactions to occur. If pH is adequate and soil tests indicate need for supplemental sulphur magnesium or calcium, then applying the most soluble sources ahead of planting and incorporating into the root zone is a good option. Applying these elements as foliar fertilizers generally is ineffective. The main exception is sulphur on canola. A foliar application of sulphur and boron prior to flowering has resulted in improved canola yields.

Sulphate sulphur sources can be band applied in corn starter fertilizers or in sidedressed UAN nitrogen.

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Choosing the Right Source of Calcium, Magnesium and Sulphur based on the Soil Test or Tissue Tests Soil test results will measure calcium and magnesium as part of the analysis with potassium. Once again, calcium and magnesium are closely related to soil pH. If soil pH is in range, the soil report will indicate a requirement for magnesium if the test is below 20 ppm. These results will dictate if limestone or other soluble fertilizer sources are required. There is currently no accredited test for soil sulphur. As such, the recommendation is based on unique crop requirements. Currently wheat, canola and alfalfa are indicated as crops with greater need for supplemental sulphur.

Tissue tests can measure plant nutrient tissue levels and compare them to a critical value. This value is relevant if the timing and specific plant part(s) were collected and subsequently analyzed in an accredited lab. Nutrient deficiencies will be indicated on a report.

Applying foliar calcium on field crops is not practical. Magnesium can be applied foliar as well as sulphur. However, applying secondary elements as a foliar may provide short term alleviation of a deficiency. Generally, it is impractical to spray these as a foliar application due to limitations in applying sufficient quantities, and because these elements do not translocate within the plant from the leaves to the area where the mineral is deficient. Foliar calcium is a standard practice in some horticultural crops. It is only effective if calcium comes in contact with the plant part requiring the calcium.

Choosing the Right Source of Calcium, Magnesium and Sulphur based on the Timing of Application Choosing the correct source of these materials depends on soil tests, crop, cropping system and equipment systems available to apply them Calcium, magnesium and sulphur are best soil applied ahead of cropping needs. Calcium and magnesium can be adjusted at the beginning of a cropping rotation cycle and move very little in the soil. Liming practices often adjust calcium and or magnesium to desired levels. Sulphur, in particular sulphate sources, is mobile in the soil and is best applied annually ahead of planting. Any number of sulphate sources can be included in a crop plan depending on the crop needs for other nutrients.

Choosing the Right Source of Micronutrients based on Crop Type Corn has a high requirement for zinc and responds best to soil applied zinc placed in starter bands at planting time. Zinc sulphate is often the best choice followed by zinc oxy-sulphate blends that contain at least 35% sulphate sources. Liquid sources that are compatible in liquid starter fertilizers are also an option. Foliar products can be used but often times the application is too late to be of benefit.

Soybeans and cereals have a higher requirement for manganese. It is most effective to apply soluble products as a foliar application to avoid soil reactions that reduce availability. Foliar applications that are made within a few days after visual symptoms appear will prevent yield loss.

Forages, mainly alfalfa and vegetable root crops, often have a high requirement for boron. Soil applications can be effective but there is also a need to apply boron foliar to some of the root crops to maintain crop quality and enhance storage life.

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Choosing the Right Source of Micronutrients based on the Cropping System Crops in a crop rotation can have similar or differing micronutrient requirements. Corn and white beans can have similar needs for zinc. It may be possible to build up zinc soil levels to handle the needs of the second crop. Zinc sulphate or zinc oxy-sulphates could be used. Applying liquid products or chelates may not provide sufficient quantities.

Applying boron for two crops may lead to toxicity regardless of the source used. Utilizing mixed products that contain more than one element may not be beneficial to rotational crops.

Soil applying dry or liquid manganese sources is usually ineffective in reducing nutrient deficiencies.

Choosing the Right Source of Micronutrients based on the Crop Growth Stage Micronutrient deficiencies are best addressed in the early growth stages on most crops. Some micronutrients such as boron may require multiple applications at critical growth stages for crop quality reasons.

Manganese on soybeans may require repeated applications based on severity and persistency of the deficiency Foliar applications require liquid formulations or water soluble powders dissolved in sufficient carrier to make a spray solution. Using multi-element products may result in an application of a nutrient not required for optimum yield.

Choosing the Right Source of Micronutrient based on the Soil Test or Tissue Test Soil testing for micronutrients can be done. The accredited tests cover zinc and manganese but not for boron in Ontario. Zinc index values below 15 indicate a greater chance for an economic response.

Soil applied products for zinc include sulphate and oxy-sulphate sources. Liquid chelated products are not as effective in building soil test levels and are more expensive choices. Liquid sources are good for foliar applications although waiting to treat zinc deficiencies may result in reduced ability to capture yield responses.

Manganese, due to its highly reactive nature, is best applied as a foliar spray of a soluble product.

Plant tissue samples taken at the appropriate time and the correct plant part can confirm visual symptoms or detect deficiencies that are not visible to the naked eye.

Foliar manganese applications of liquid or dry water soluble powdered products mixed in water carrier and applied to sufficient leaf canopy will bypass soil reactions and provide a more rapid relief of deficiencies.

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Choosing the Right Source of micronutrients based on the Timing of Application In a well-designed, field nutrient plan based on soil tests, the micronutrient needs can be addressed ahead of time. Soil application may be best for zinc and boron whereas a foliar program may be best for manganese. Micronutrients are non-mobile in plants, therefore having an adequate supply in the soil ahead of time is one of the better strategies for managing micronutrients. Any number of sulphates or oxy-sulphates is an appropriate choice for soil application. If indeed deficiencies do occur, then foliar applications are an option. For manganese, a foliar program is considered to be most effective using liquid and soluble dry formulations. The earlier the deficiency is relieved, the higher the potential yield capture.

Foliar boron, using water soluble sources, may be necessary for some speciality crops to improve both yield and quality. Often times, an application just prior to reproductive stages improves storage quality on root crops.

A soil applied spring application after first cut of alfalfa on coarse soils often is sufficient to reduce deficiencies and improve crop growth and yields. A fall application may result in leaching losses.

Applying boron to crops that do not demonstrate a clear need may in fact actually cause a yield loss due to toxicity.

Performance Objective 3 Discuss how managing the 4Rs for potassium, secondary macronutrients, and micronutrients influences nitrogen and phosphorus losses to surface water and groundwater.

One of the underlying principles of nutrient utilization and interactions in the 4R approach is best described by Von Liebeg’s barrel. Also known as “The law of the minimum “. It is not how much nutrient is in the soil of any one element but rather it is the element in the least amount of supply that determines crop growth and subsequent nutrient utilization.

Von Liebeg’s Barrel - “The law of the minimum”

Source: Yara Crop Nutrition, http://yara.co.uk/crop-nutrition/ three-steps/step-1/, accessed March 31, 2016

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Potassium Influence on Nitrogen and Phosphorus Losses to Surface or Groundwater Potassium and Nitrogen Nitrogen can be absorbed both as an anion and a cation. This presents a potential cation-anion interaction with K or a cation-cation interaction. As nitrogen increases in the soil solution, the uptake of phosphorus increases. This effect could be caused by a decrease in pH when there is a greater amount of ammonium ions in the soil solution. Also, increased nitrogen uptake increases the rate of translocation of phosphorus from the root to the plant shoot.

Plants supplied with predominately ammonium N (NH4+) require an adequate supply of K to increase crop growth and reduce any potential toxicity caused by excess ammonium accumulation in the early growth stages. No such issues are observed with nitrate sources. Numerous studies show the need for increased K supply as N rates increase. Therefore, if N application rates are increased in a low K environment then crop growth will be limited and N may be underutilized reducing nutrient use efficiency and leaving unused N subject to environmental losses.

Potassium and Phosphorous Potassium and phosphorus interactions are less evident in research literature. P uptake is independent of K uptake. However, since both P and K are essential nutrients, normal plant metabolism requires both to be present to build the necessary cation anion balance in plant cells and produce the desired compounds for growth. One notable exception is the impact of K on the well-known P-Zn interaction.

Increasing levels of K reduce the influence of excessive P on zinc uptake (Stukenholtz et al, 1966). It appears that K increases the exchange of Zn and Mn, increasing the supply of both and reducing the negative effect of higher P availability.

With adequate K nutrition, overall plant metabolism is increased and all essential nutrients including N and P are better utilized.

Influence of Calcium and Magnesium on N and P losses Potassium (K), Calcium (Ca) and Magnesium (Mg) These three cations are dominant in soil and soil solution. They are competitive at the root sites for uptake. Excessive potassium can interfere with magnesium and to some degree Ca uptake. Conversely, excess magnesium can depress K uptake. While no ratios are prescribed as being ideal, the effects are known. A soil test and tissue test will offer insight into nutrient relationships. As stated earlier, Ca and Mg are associated with the need for liming due to low soil pH. With proper pH, both N and P are better utilized by the crop.

Documentation can be found on high K rates lowering Ca and Mg in plant tissues. It is often due to dilution because of the stimulatory growth effects of K increasing crop growth and yield and demand for N and P.

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Influence of Sulphur on N and P losses Nitrogen and sulphur are both involved in protein synthesis. If the sulphate sulphur supply is low in the soil then the nitrogen utilization may be limited as the sulphur supply becomes the first limiting factor on crop growth. Increasing N rates without due consideration for S supply will reduce growth and utilization of both N and P. The ratio of N:S in plant tissues ranges from 7:1 to 15:1 depending on the species and the stage of growth. Crops that receive high rates of nitrogen when sulphur supply from the soil is low can suffer from induced sulphur deficiency. This has led to a common practice in western Canada of applying one pound of sulphate sulphur to canola for every six to eight pounds of nitrogen. Ontario growers may have to consider a similar practice for intensively managed canola, alfalfa, and wheat crops, particularly if atmospheric deposition of sulphur continues to decline.

Influence of Zinc (Zn), Manganese (Mn) and Boron (B) on N and P losses Zinc is important in early plant growth and in grain and seed formation. It plays a role in chlorophyll and carbohydrate production. Plants that grow efficiently will use more N and P when adequate zinc supply keeps plants growing and allowing them to metabolize normally.

Manganese is involved in photosynthesis and chlorophyll production. It helps to activate enzymes and is involved in the distribution of growth regulators within the plant. Nitrogen and magnesium are key elements in chlorophyll, therefore both adequate Zn and Mn keep plants metabolizing normally and taking up N and P to meet desired production levels.

Boron plays an important role in the structural integrity of cell walls, fruit set, seed development, and carbohydrate and protein metabolism. Plants that are adequately supplied with B will continue to use N, P and other essential nutrients more effectively to make sugar and develop seeds which, in turn depending on the crop, can be high in both N and P. Plants that have access to all essential nutrients will metabolize more efficiently. Any essential nutrient that is missing in a field nutrient program runs the risk of causing other nutrients that have been applied for a specified yield goal to be underutilized and increase the risk of environmental loss if those nutrients are N and P. Refer to Von Liebegâ&#x20AC;&#x2122;s Barrel.

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Competency Area 2 Determining the Right Rate of Potassium Performance Objective 4 Interpret how soil test potassium levels relate to crop yield response and potential environmental impacts.

The following table relates the soil test K level to a relative response rating and a recommended rate of K2O available to the crop. In this case corn. Each crop type has its own recommendations.

Soil test rating

Interpretation

Possible Economic Response

HR

Highly responsive

High economic response to the application

MR

Moderately responsive

Medium response to the application

LR

Low response

Low economic response to the application

RR

Rarely responsive

Rarely pays to apply nutrients

NR

Not responsive

Applying nutrients almost always results in economic loss

A soil test level of 50 ppm results in a rating of HR - highly responsive to the recommended rate of 110 kg/ha.

Table 4.4. Phosphate and Potash Recommendations for Corn Based on OMAFRA-Accredited Soil Tests Ammonium Acetate Potassium Soil Test (ppm)

Rating1

Potash (K2O)2 Required kg/ha

0-15

HR

170

16-30

HR

160

31-45

HR

140

46-60

HR

110

61-80

MR

80

81-100

MR

50

101-120

MR

30

121-150

LR

0

151-250

RR

0

251+

NR

0

3

Source: Agronomy Guide for Field Crops, Publication 811, OMAFRA, 2009, p. 22.

Applying potassium fertilizer in excess of the recommended rate mostly results in an economic loss in the year of application. The choice of the fertilizer product and its accompanying ion may pose a risk such as using potassium nitrate when nitrogen is supplied by another source.

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Performance Objective 5 Evaluate how soil moisture content and sampling time may affect soil test potassium levels.

Field conditions at time of taking the soil sample may impact on the results. Field conditions that are excessively dry may make it difficult to maintain a proper, consistent sampling depth which could cause elevated K tests in no till or minimum till cropping systems. Drying and wetting of soil may also influence soil test K results. Illitic and vermiculite clays can influence the amounts of exchangeable K based upon their ability to fix K ions in the inner layers of the structure especially under dry conditions.

Exchangeable K can either increase or decrease upon drying and is dependent upon the clay minerals present. Potassium fixation (K becomes non-exchangeable) can occur from drying soils with high exchangeable K or recent K fertilizer applications. Fixation is a result of K becoming trapped within clay sheets as they dry and collapse. This may result in a lower soil test value.

More K could be released in soils low in exchangeable K as they dry because the clay sheets roll back and release K (McLean and Watson, 1985).

Thus, the time of soil sampling in relation to field wetting and drying cycles may influence soil test levels. It becomes important to pay attention to these conditions and make an effort to sample at the same time each year or if possible under similar conditions and be aware of current fertility practices that may alter results due to recent fertilizer applications.

Performance Objective 6 Estimate how potassium rates may be affected by soil characteristics, which may include: a. cation exchange capacity (CEC); b. organic matter; c. texture; d. clay type.

Cation Exchange Capacity (CEC) Finer textured soils will have a higher CEC and hold and release more exchangeable K. As such, clay soils tend to be higher in K and need less supplemental K added to meet production levels. In contrast, low CEC sandy soils have a lower ability to hold sufficient K and may test lower in available K resulting in the possible need for higher amounts and more frequent applications.

Organic Matter Soil organic matter can act as a storehouse of some available K. However, organic matter increases the CEC and nutrient holding power of a given soil imparting some of the same actions on exchangeable K as the CEC.

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Texture Soil texture is influenced by the relative amounts of sand silt and clay. Higher clay soils will have higher CEC (see CEC). Rates of application will be dependent upon soil test levels which are directly influenced by texture and accompanying CECs. Clay Type Various clays exhibit differences in their ability to bind and release K which is also influenced by soil moisture. Refer to Performance Objective 5 above.

Source: International Plant Nutrition Institute

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Performance Objective 7 Calculate potassium credits from: a. previous potassium application; b. manure; c. biosolids; d. irrigation water; e. wastewater.

Previous Potassium Application It is expected that applications were made based on a soil test, as such, the rate applied was based on need. If for an unforeseen situation, such as drought, yields were lower than expected, the need to calculate carryover or a credit is really of little consequence. Always base fertility needs on a soil test. If fertility was not removed then the soil test values should be higher reflecting the need for lower rates of application going forward.

Manure Use the NMan calculator or manual worksheets. You will need to know the type of manure, either book values or a manure test, and rates of application to determine the K credits applied per hectare or acre.

The formula below shows how to calculate the available K20. Some labs may already have done these calculations. If a manure analysis is not available, use the typical manure analysis by livestock type.

Refer to the chart contained in Performance Objective 9, Proficiency Area 5, Manure Management.

Convert to Metric %

kg/1,000 L

%

kg/tonne

mg/L %

multiply by multiply by divide by

Convert to Imperial

10 10 10,000

Available K2O: Percent K ___ x 1.08 = _____ % available K2O

%

lb per 1,000 gallons

multiply by

100

%

lb per ton

multiply by

20

ppm

%

divide by

10,000

X 10 = _____kg/1,000 L/tonne X 100 =_____ lb/1,000 gal X 20 = _____lb/ton

As an example, if the K content of manure was 0.17% and it was liquid manure

K credit in kg/ te = % Total K x 1.21 x 10 x 0.9

K credit as Kg/te = 0.17 x 1.21 x 10 x .90 = 1.85 Assume an application of 5000 lt/ha (1 lt = 1kg). Therefore 5 te applied.

Total applied K2O = 5 X 1.85 = 9.25 kg / ha Biosolids â&#x20AC;&#x201C; same as for manure above

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Irrigation Water This will require a water test to determine the level of K and application rates over the season in terms of acre inches (cubic meters) of water applied. The kg of K applied per ha is determined by ppm K * 0.00113 * cubic meters of water applied/ha Example: A water test reveals 5 ppm K and 1020 cubic meters are applied per/ha/season 5 ppm *0.00113 * 1020 = 5.76 kg/ha of K (multiply by 1.2 to equate to K2O) which is 6.91 kg/ ha of K2O Waste Water â&#x20AC;&#x201C; refer to manure and irrigation water.

Performance Objective 8 Justify the rate of potassium applied based on potassium placement.

Potassium is a relatively non-mobile nutrient and, as such, it should be placed into the root zone for optimum uptake by plant roots. The recommended rate of potassium is based on soil tests. Efficiencies from placement are not considered for K as there is a need to apply at appropriate rates due to relatively large quantities taken up by plants.

Often times, the safe rate of banded K fertilizer with nitrogen determines the optimum rates for banding versus broadcasting.

There is Ontario research supporting the inclusion of small amounts of K in a starter fertilizer on corn in low K testing soils. However, yields were maximized with additional broadcast K. On forages, the only option is to surface broadcast to meet crop requirements. K is sufficiently mobile to reach near surface feeder roots. However, prior to the year of establishment, it is advised to apply and incorporate K into the root zone. Often early spring or fall applications just prior to fall rest period are good times to apply due to the likelihood of higher rainfall events to move K into the soil for established stands.

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Competency Area 3 Determining the Right Timing of Potassium Application Performance Objective 9 Discuss how the timing and method of potassium application can impact crop response.

Two guiding principles of potassium placement and timing relate to K mobility in the soil and relative large amounts of K needed by crops.

Potassium moves only short distances by the process of diffusion. This necessitates the need to place K where the roots are actively growing to be in a position for optimizing uptake. Placing small amounts of K in starter bands assures early season uptake. Placing the bulk required into the soil root zone, either by broadcasting and incorporating or utilizing placement technology such as strip tillers to place K in concentrated bands to produce a nutrient rich zone, will facilitate K uptake.

Surface applying and not incorporating K may not place sufficient quantities into the root zone for optimal uptake. Potassium ions only travel short distances at a relatively slow speed of approximately 0.1 cm/day (Tinker G.S. Sekhon, Potash Research Institute, India, 1978).

Table 4.5 contains data from Ontario research trials that evaluated corn grain yield response to various starter fertilizers. When soil-test K levels were less than 90 ppm and no broadcast K was applied, applying a MAP/potash blend in a 5 cm x 5 cm (2 in. x 2 in.) starter band increased corn yields significantly. In these same circumstances, seed placed liquid fertilizers that also contain a small amount of K can be expected to produce higher corn yields than where no starter fertilizer is used or where starter fertilizers contain P only. On these lower testing soils, when K is broadcast prior to planting (fall or spring) yields, are improved significantly by the broadcast K and the magnitude of the yield response due to the starters is reduced (Refer to Table 4.5).

The data generally indicates that broadcasting K on the lower testing soils is advised, but in situations where land tenure is in question and broadcasting a significant amount of K to build soil tests is risky, a grower who has the capability to band dry fertilizer P and K blends can generate yields equivalent to other options.

On higher testing soils, the size of the yield responses to any applied K is much less. However, some of the same trends are observed. Some K in a starter band can improve yields, but generally the advantage to higher K rates in dry 5 cm X 5 cm (2 in X 2 in) bands compared to lower in-furrow rates is marginal.

If broadcast K is to be applied either in the fall or spring prior to corn planting, the need for K in the starter is significantly reduced unless soil tests are low (i.e. less than 61 ppm). In these low testing situations, broadcasting to build soil test and banding to help meet the immediate crop requirements are likely both profitable.

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The following table illustrates the impact of soil test K, placement methods, and fertilizer sources on corn yield.

Table 4.5. Impact of Broadcast K Applications and Various Starter Fertilizer Options on Corn Yields.

Soil Test K (ppm)

< 90

> 90

Convert to Imperial

No Broadcast K

Broadcast K

Bu/ac

Tonnes/ha

Bu/ac

Tonnes/ha

none

120

7.6

156

9.8

6-24-6 (liquid in furrow)

139

8.7

158

9.9

P and K (dry in 2X2 band)

168

10.4

166

10.5

none

176

11.0

186

11.7

6-24-6 (liquid in furrow)

186

11.7

192

12.0

P and K (dry in 2X2 band)

190

10.9

195

12.2

6-24-6 applied at 47 litres/ha (5 gal/acre) P and K applied at rates of 35-62 kg/ha (31-55 lbs/ac) of P2O5 and K2O each in a blend Soil test averages for sites in the < 90 group averaged 71 ppm K and 21 ppm P Soil test averages for sites in the > 90 group averaged 122 ppm K and 27 ppm P Chart source: Stewart, G., Janovicek, K., P and K Considerations in Corn, OMAFRA 2014, http://www.omafra.gov.on.ca/english/crops/field/news/croptalk/2014/ct-1114a1.htm, accessed April 1, 2016

Competency Area 4 Determining the Right Placement/Method of Application for Potassium Performance Objective 10 Discuss considerations to determine the proper placement and method of application of potassium based on the: a. crop type; b. cropping system; c. methods of tillage.

Crop Type Placement of K for various crop types will be dependent upon a number of factors including: • perennial versus annual; • K demand; • safe rates; • root structure - tap, fibrous; • field variability of K; • soil texture; and, • cropping system.

Perennial versus Annual Perennial crops may have larger or smaller demands for K. Tree fruits may have smaller annual demands whereas alfalfa will have much larger demands. Applications may be limited to broadcast applications with no soil disturbance whereas other crops with drip irrigation may provide for a more timely application method throughout the season to meet demands.

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Potassium Demand Some crops have higher K demands than others; this may necessitate a combination of placement options to apply sufficient quantities to meet early and later season uptake patterns. Potatoes and tomatoes may require applications split between pre-plant, banding in the seed bed and a final layby with nitrogen just prior to row closure Table 4.6. Field Crop Nutrient Uptake and Removal in Ontario Crop

Yield

N*

P2O5

bu/ac

K2O

Ca

Mg

S

lb/ac

GRAINS, OILSEEDS Grain corn

150

uptake removal

173–23 97–149

74–109 55–66

133–243 39–44

26–49 1

18–3 13

13–16 10–11

Soybean

50

uptake removal

230–29 187–200

40–50 40–44

120–220 69–70

25–30 9–11

20–25 7–9

17 5

Winter wheat

75

uptake removal

140–15 86–94

51–56 41–47

94–152 26–28

13 2

17–23 12

15–19 6

Barley

75

uptake removal

93–112 65–83

36–41 28–30

75–112 19–26

17 2

8–13 4

13–15 6

Oats

75

uptake removal

70–86 47–60

30–33 19

89–109 14–15

9 2

10–15 3

14 5

Winter rye

50

uptake removal

83–84 54–61

28–42 17–23

50–120 17–18

13 3

7 4

14–15 5–10

Dry beans

30

uptake removal

75

25

25

2

2

5

Canola

45

uptake removal

135–144 90–100

59–75 50–60

107–120 25–30

** 9–12

** 12–15

27–28 15

FORAGES

TON/AC DM†

Corn silage

8

173–239

74–109

133–243

26–49

18–30

13–16

Legume haylage

5

266–367

53–79

224–354

113–177

19–36

19–20

Mixed haylage

5

228–338

52–78

224–355

95–164

16–34

15–29

Grass haylage

4

129–219

39–62

163–287

42–90

10–21

**

Legume hay, 1st cut

5

223–331

52–80

206–350

101–154

21–34

19–27

Mixed hay, 1st cut

5

172–273

50–72

170–297

82–135

18–30

13–21

Grass hay, 1st cut

4

103–181

35–56

111–224

42–85

11–21

11–16

Hay, 2nd cut

3

152–215

34–47

119–191

68–102

14–23

11–17

* Soybeans, dry beans, forage legumes get most of their nitrogen from the air. † Tons per acre of dry matter **Data not available Ranges of nutrient uptake and removal for yield levels typical of good growing conditions for field crops. Figures are based on Ontario field data where possible and are estimates.

Actual uptake and removal will vary with yield, and nutrient concentrations will also vary with year, level of soil fertility and crop variety. Precise nutrient management planning would require analysis of each crop each year. Actual changes to soil fertility may differ from the amount removed by the crop. In some instances, weathering of soil materials and organic matter may compensate for part of the nutrient removal by crops. In other instances, nutrients may be chemically fixed by the soil or lost to leaching, and the loss of nutrients will exceed crop removal.

Chart source: Soil Fertility Handbook, Publication 611, OMAFRA, 2006, p. 146.

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Table 4.7. Horticultural Crop Nutrient Uptake and Removal Ontario Crop

Yield

N*

P2O5

ton/ac

K2O

Ca

Mg

S

lb/ac

Beans, green

5

uptake removal

170–173 120

16–41 10

100–204 55

** **

21 **

** **

Broccoli

5

uptake removal

165 20

10 2

210 45

** **

** **

** **

Cabbage

35

uptake removal

225–270 225

63–84 84

249–280 280

84 84

35–36 35

64–77 64

Carrot

25

uptake removal

145 80

25 20

345 200

** **

** **

** **

Corn, sweet

6

uptake removal

155–187 55

20–63 8

105–181 30

** **

27 **

15 **

Onion

20

uptake removal

120–145 110–120

25–53 20–53

105–155 105–110

30 29–30

12 5–12

25–48 29–48

Peas, green

2

uptake removal

170–260 100

22–56 10

80–168 30

** **

29 **

16 **

Potato

20

uptake removal

215–228 128–133

66–72 37–50

298–437 216–250

** 5

40 10

18 10–12

Sugar beets

22

uptake removal

186–211 88–92

29–67 11–40

386–403 143–183

** **

59 **

32–33 13

Tobacco

1

uptake removal

84–110 56–75

17–30 10–15

170–171 104–120

** 75

16 18

13 14

Tomato

40

uptake removal

232 144–160

87 48–68

463 280–288

** 14–24

36 22–24

54 28

Apple

12

uptake

100

46

180

**

24

**

Grapes

6

uptake

51

18

80

**

9

**

Peaches

15

uptake

50

20

60

11

**

**

Ranges of nutrient uptake and removal for yield levels typical of good growing conditions for horticultural crops * Legumes such as beans and peas get much of their nitrogen from the air ** Data not available Chart source: Soil Fertility Handbook, Publication 611, OMAFRA, 2006, p. 147.

Annual crops such as cereals, oilseeds and corn can have numerous placement options, broadcast in the fall or spring and incorporated, or applied pre-plant and some in the starter or popup band. If the soil test indicates a small amount of K, less than 25 kg, it may be included in a 2 x 2 starter band as long as the maximum safe rates are followed. Higher rates of K could be included depending on nitrogen rates.

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Safe Rates Table 4.8. Maximum Safe Rates of Nutrients N (kg/ha)

Crop

N+K2O (kg/ha)

SPRING OAT AND BARLEY (FERTILIZER WITH SEED) Sands, sandy loam Urea (46-0-0) 10 30 Di-ammonium phosphate (18-46-0) 20 35 Other fertilizers 35 55 Loams, silt, clay loams Urea (46-0-0) 10 30 Di-ammonium phosphate (18-46-0) 30 55 Other fertilizers 45 70 WINTER WHEAT, TRITICALE OR BARLEY (FERTILIZER WITH SEED) All soils Urea (46-0-0) 0 (fall) 0 (fall) Di-ammonium phosphate (18-46-0) 0 (fall) 0 (fall) Other fertilizers 15 30 CORN (FERTILIZER BANDED WITH THE SEED) All soils Urea (46-0-0) 0 0 Di-ammonium phosphate (18-46-0) 0 0 Other fertilizers - 100-cm rows 7 - 75-cm rows 10 - 50-cm rows 14 Note: Sweet corn can be more sensitive to fertilizer placed with the seed. Do not apply fertilizer with the seed of super sweet hybrid sweet corn.

CORN (FERTILIZER BANDED 5 CM TO THE SIDE AND 5 CM BELOW THE SEED) All soils Urea (46-0-0) 40 60 Other fertilizers 55 90 At higher rates, band at least 15 cm from seed. At row widths other than 100 cm, the rate may be adjusted to provide the same maximum concentration in the row (e.g., in 50-cm row, the safe rate = 100/50 x 55 = 110 N).

CORN (FERTILIZER BROADCAST) Sands, sandy loam Urea (46-0-0) 200 250 CANOLA (FERTILIZER WITH THE SEED) Up to 20 kg/ha phosphate fertilizer may be drilled with the seed as superphosphate or mono-ammonium phosphate. Do not apply N (except as mono-ammonium phosphate) or K with the seed.

FLAX (NO FERTILIZER WITH THE SEED) Rates recommended are normally safe when broadcast.

PEAS, BEANS AND SOYBEANS (NO FERTILIZER WITH THE SEED)

All soils, fertilizer banded 5 cm to the side and 5 cm below the seed

30

90

Source: Soil Fertility Handbook, Publication 611, OMAFRA, 2006, p. 171.

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Fertilizers containing more than half as much N as P2O5 (e.g.16-16-16) often contain urea. Fertilizers containing urea are not suitable for banding at seeding in many cases.

Root Structure Fibrous roots tend to be near the surface and have a greater surface area. They may be able obtain adequate K from shallow broadcast placement with adequate soil moisture. In a dry year, the K may not be available to the roots. A continued practice of surface broadcast with minimal incorporation may result in nutrient stratification.

Taproots tend to be deeper and occupy lower soil volume. Placement throughout the root zone with a combination of banding and broadcasting at various depths may augment K uptake.

Field Variability Field variability of K may also influence placement and method. If the K test across a field landscape is highly variable, the demand for K may increase. A number of options exist. A single rate of application may be justified based on economic response from the lower testing areas or, a preferred variable rate targeted application that is best done by broadcast or strip till depending rate and on the technology available.

Table 4.9. Influence of Soil Test K Variability on Optimum K Fertilizer Rate in Ontario Average soil test K ppm

Uniform

Soil test variability Moderate optimum K2O rate (kg/ha)

High

45

100

101

106

90

50

58

77

135

0

30

58

Source: Kachanoski and Fairchild, 1994. Coefficient of variation for low variability site = 0%, medium = 53% and high = 131%.

Chart source: Soil Fertility Handbook, Publication 611, OMAFRA, 2006, p. 140.

The image below illustrates variability of soil test K across the field. The field average is 128 ppm of K but ranges from 88 to 196 ppm of K. This creates an opportunity to practice 4R stewardship and target the application to the area(s) of greatest need.

Source: AGRIS Cooperative, 2016

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Soil Texture There are inherent differences in soil textures. Sand, loam and clays will have different K contents and will influence the K soil test and subsequent recommendations. Sands with low buffering capacity will require more frequent applications. Clays will require, as a rule, less frequent applications due to higher buffering capacities. Loams fit in between. Soil textures may limit spring applications. Sandy soil may tolerate an extra pass for application in the spring whereas clays may not be conducive to extra traffic or deeper placement technology for fear of soil compaction. Fall application may be preferred on clay soils. Loams may afford many more options for either fall or spring applications.

Cropping System The cropping system or rotation sequence may require different approaches based on K demand of the crops in the rotation. Planning ahead for opportune times to effectively apply and place K in the root zone should be considered. Often, looking at the entire K needs for four-year rotation will offer insight into K needs and placement methods.

The following table illustrates the differing amounts of K2O required in a typical crop rotation for a dairy operation. One can readily see the crops with the greatest need and can plan a nutrient application strategy to address the K demands ahead of time. Corn silage K applications could be addressed the fall before or in the spring. Alfalfa could be fertilized a year ahead with annual top-dressing after each cut or ahead of the fall rest period. Barley needs could be done at planting time.

Crop

Yield te/ha

K kg / ha

Corn silage

17

200

3 years of alfalfa

33

963

Barley

2

24

Total

1187

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Performance Objective 11 Estimate the proper placement and method of application of potassium based on current potassium soil test levels and soil texture.

Example: Basic soil test information, fall application for a new seeding: Crop

K ppm

Texture

Alfalfa

65

F

The OMAFRA recommendation at 65 ppm is 200 kg per ha of K2O. Broadcast applying a year ahead in the early fall and incorporating all the potash into the root zone may be the best option. Alfalfa has a high K demand and potassium has limited soil mobility so placement into the root zone where the roots will be actively growing will enhance K uptake.

This is a fine-textured (F) or clay soil therefore there will be no issue with K leaching as clays tend to have higher CEC. If this was C textured soil, for a coarse or sandy soil texture, we may opt for a lower rate for spring application ahead of seeding to reduce potential K leaching due to lower CEC and apply more frequently after each cut and before the fall rest period.

Table 4.10. Potash Requirements for Forages Based on OMAFRA - Accredited Soil Tests Ammonium Acetate Potassium Soil Test (ppm)

At Seeding With or Without Nurse Crop Rating1

Potash (K2O)2 Required kg/ha

Rating1

Potash (K2O)2 Required kg/ha

0-15

90

480

16-30

80

400

31-45

HR

70

HR

320

46-60

50

270

61-80

40

200

81-100

30

130

101-120

MR

121-150

20

MR

20

70 20

151-180

LR

0

LR

0

181-250

RR

0

RR

0

251+

NR

0

NR

0

3

Chart source: Agronomy Guide for Field Crops, Publication 811, OMAFRA, 2009, p. 68.

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Fall Applications for New Seeding and Established Stands

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Competency Area 5 Determining the Right Rate, Timing and Placement of Secondary Macronutrients Performance Objective 12 Discuss considerations to determine the proper rate, timing and placement of magnesium based on the: a. crop type; b. cropping system; c. crop growth stage; d. soil test or tissue test; e. timing of application; f. method of application.

Consideration for magnesium (Mg) is often addressed if a limestone application is required.

Depending on soil test Mg level, dolomitic lime may be the appropriate choice and would be applied broadcast and incorporated into the root zone (see P.O. 18 for more details). If lime is not needed and the Mg soil test is below 20 ppm, then supplementing with one of many soluble magnesium sources such as magnesium sulphate or sul-po-mag if potassium and sulphur are also required. The recommended rate is 30 kg/ha of Mg. Placement options can be in starter bands or broadcast and incorporated. Magnesium has limited mobility but greater than both K and Ca. It is still best to soil apply and incorporate into the root zone.

Mg uptake can be reduced in high K soils and may impact on livestock consuming forages grown under those conditions. Monitor soil test and avoid excessive K applications.

Crop Type Mg is an essential nutrient and plants require adequate amounts to grow normally. Most of the uptake occurs during vegetative stages of growth much like K. Having a balanced supply in the soil at all times, will aid in uptake and meet crop demands.

Cropping Systems Crop rotations that contain forages may have a more critical need to watch both K and Mg soil test levels. Excessive K will reduce Mg uptake in forages, this may be a health concern when livestock consume forages testing low in Mg. Managing the crop rotation with current soil tests and addressing pH, K and Mg levels throughout the rotation, should avoid any Mg nutritional issues.

Crop Growth Stage The greatest need for Mg is during the vegetative growth stages. Therefore, maintaining proper pH and soil test Mg level should meet nutrient demands of a majority of Ontario crops.

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Soil Test and Tissue Test Mg is easily determined by a soil test. Maintaining Mg above 20 ppm and proper soil pH are two of the factors a soil test can monitor. Plant tissue testing at the appropriate time and collecting the proper plant parts can offer insight into Mg uptake. Plant tissue reports from accredited labs offer an interpretation based on a critical tissue content level. There are often other circumstances that can influence tissue test levels. â&#x20AC;&#x153;High levels of the other cations, such as ammonium (NH4+), potassium (K+), and calcium (Ca2+), can compete with Mg for plant uptake and effectively reduce the amount of Mg taken up by the plant. Magnesium, NH4+, and Ca2+ ions are primarily taken up via a mechanism called mass flow that is dependent on the amount of water the plant removes from the soil and transpires through the leaf stomata openings to cool the leaves. The cations move with the water flow and are taken up and accumulated by the plant. Excessive moisture present in the soil and high relative humidity may reduce the amount of water that the plant can transpire. This may be one factor causing lower uptake. Often times a little detective work is required to understand what has occurred and what some of the other influences are that are impacting on tissue levelsâ&#x20AC;?.

Richard Taylor, Extension Agronomist; rtaylor@udel.edu If the soil test is low in Mg or pH needs adjustment, then an application to the soil of an appropriate source ahead of planting will remedy the shortages. If plant tissue reveals deficient Mg levels then a foliar application may be required to keep plants growing normally. However, Mg is a secondary nutrient usually required in amounts beyond what single foliar application may provide. Depending on crop and crop growth stages, it may be possible to soil apply Mg and gain a response such as banding Mg with sidedress nitrogen at V5 growth stage for corn. As the season progresses, fewer options are available that make agronomic or economic sense.

Timing of Application Mg can be applied with other nutrients when it fits in with other nutrient application operations in either fall or spring. As stated previously, the greatest demand is during vegetative growth stages. With limited soil mobility, it is best applied ahead of time into the root zone for optimum uptake.

Method of Application The preferred method is a soil application, in either a starter band, strip till or broadcast and incorporated. A need for lime will require a separate field operation. Foliar applied Mg sources are the least effective method of application due to the quantities that may be required.

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Performance Objective 13 Discuss considerations to determine the proper rate, timing and placement of calcium based on the: a. crop type; b. cropping system; c. crop growth stage; d. soil test or tissue test; e. timing of application; f. method of application.

Considerations for calcium (Ca) follow very closely those of magnesium. Ca is often associated with the need for limestone applications. The choice of lime is dictated by the Mg soil test level. If it is above 100 ppm then choose calcitic lime (see P.O. 18).

There are some special considerations beyond the pH adjustment. Soils testing low in Ca (<350 ppm) may have cropping situations where a response can be obtained from added Ca application. A number of cole crops will have a higher need based mostly on quality, storage and extended shelf life.

In some plant diseases, such as club root, elevated soil Ca levels along with other mitigating practices help reduce incidence and severity. At this point, there are no provincially approved recommended rates for Ca applications. Farmers are often using best judgement, economics, product availability and crop experience to determine rates on their farms.

Crop Type All crops need calcium. For the most part, Ontario soils are well supplied with Ca. Keeping soils in the proper pH range is a best management practice to assure adequate Ca supply.

Cropping System A regular soil test program will help insure an adequate supply of Ca. If pH sensitive crops are in the rotation, it may be critical to make soil adjustments one or two years ahead of time. Potatoes are a crop that do best at pH less than 6.0 whereas wheat in the rotation may do best at pH 7.0. This rotation would pose potential issues in optimizing both crops based on the time it takes to adjust pH and rarely can pH be brought down quickly or economically enough to be effective.

Crop Growth Stage Ca uptake is greatest during the vegetative growth stages. Very little Ca is translocated to the grain.

Soil Test and Tissue Test Soil tests are very effective in determining Ca levels. Although it is not an accredited test it is extracted at the same time as K and Mg and therefore is easily reported. Although the extracted calcium value may be compromised by soils containing excessive amounts of free lime. Tissue tests can also determine Ca uptake. Interpretation of tissue test results are dependent upon collecting the sample at the correct growth stage and plant part. The results are compared to a critical level based on those parameters.

Because soils usually contain high calcium levels, any soil splash onto plant parts could skew the results to a high bias. Careful sample preparation is required

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Timing of Application Calcium needs are best addressed ahead of planting, usually associated with lime applications to adjust pH. Depending on lime quality, it may require more than 12 months to react and make a full adjustment to the targeted pH. In some horticultural crops, there is a practice of applying multiple foliar applications of calcium, in particular on apple and other fruit trees. In potatoes, applying calcium sulphate in the seedbed at planting aids in better tuber sizing and storage quality.

Method of Application Applications for calcium are often associated with limestone (see P.O. 18) with no official recommendation for supplemental Ca. Other application techniques are adopted from farmer experience. Generally, granular gypsum is applied in starter bands on potatoes and tomatoes and/or broadcast treatments applied ahead of time and incorporated.

Performance Objective 14 Discuss considerations to determine the proper rate, timing and placement of sulphur based on the: a. crop type; b. cropping system; c. crop growth stage; d. soil test or tissue test; e. timing of application; f. method of application. g. atmospheric deposition of sulfur.

Crop Type Supplemental sulphur requirements have been identified and confirmed on canola, alfalfa and wheat in Ontario.

Recent studies in Ontario on winter wheat indicate a 10 lb application rate of sulphate sulphur applied in the spring with nitrogen was the optimal rate. There were some sites with up to a 20 bushel yield penalty without sulphur from sulphate sources applied.

Yield response of the six responsive sites show maximum benefit at 10 lbs/ac of sulphur, with no additional yield gain from increased sulphur rates (see graph below). This is a critical finding, as it gives an application level above which growers can expect no response. With variable winter wheat yield responses across locations and years, many growers will opt to apply some sulphur. A yield penalty of 20 bu/ac has been observed when no sulphur is applied on deficient fields. If a small amount of sulphur can be applied to avoid a significant yield loss, and average yield gain will cover the cost of this application, many growers will consider this a reasonable â&#x20AC;&#x153;insuranceâ&#x20AC;? application; 10 lbs/ac sulphur would appear to be that breakpoint.

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Sulphur Response at Six Responsive Sites (P=0.05)

Source: Johnston, P., Field Crop News, Do I need to apply sulphur to winter wheat?, April 3, 2013, www.fieldcropnews.com, accessed April 1, 2016

Alfalfa has the highest S requirements of any of the field crops. A five ton/ac crop of alfalfa removes about 25 lbs/ac of sulphur. By comparison, a 45 bu/ac spring canola crop, also a high user of sulphur, removes 15 lbs/ac. A 150 bu/ac corn crop removes 10 lbs/ac of sulphur.

Rates of sulphur on forages for Ontario are still being researched. Other jurisdictions suggest five to 25 lbs of S per tonne of production. A general thumb rule for S application on alfalfa is 5 lb/ac per ton of dry matter yield. The University of Wisconsin recommends 15 - 25 lbs/ac of S in the sulphate broadcast on established stands, or 25 - 50 lbs/ac of elemental S incorporated at seeding.

In Ontario, sulphur deposition from acid rain has decreased steadily. The amount of S deposited has decreased by over 50% since 1990. Instances of S deficiency have also increased due to reductions in the organic matter pool, higher crop yields and higher protein yields. S deficiencies in alfalfa are more likely to occur on soils that have not had a manure application within two years There currently is not a reliable soil test for sulphur in Ontario. However, tissue testing of alfalfa (at late-bud stage) is considered a suitable diagnostic approach for determining sulphur deficiencies. The critical level below which alfalfa is considered S deficient and may benefit from applying sulphur is 0.25%. A 2012 field survey of Ontario alfalfa stands indicated that 21% of fields had S-tissue analysis below this level. Put another way, 79% of these fields would have been unlikely to have an economic response to applying sulphur. It is also noteworthy that 37% of these fields tested below the critical K value of 1.7%.

Recent trials support a 15 to 25 lb per acre application sulphur from sulphate sources on canola.

Cropping System Sulphur needs within a rotation will be mostly based on the crop and crop demand for sulphur. From previous research, a canola, wheat rotation would have significantly greater demand for S than a corn soybean rotation. If you add in forages, it becomes even greater.

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Crop Growth Stage The timing of sulphur demands is similar to N as both are linked to the formation of protein. Applying N and S together has been a common practice. The plant available form is sulphate and can be prone to leaching losses over the winter so applying with N in the spring is a good practice. Most S is applied with a nitrogen source such as ammonium sulphate. The exception to this is in alfalfa where a fall application of elemental S seems to offer sufficient availability by being converted to sulphate forms over winter and early spring in time to meet uptake demands.

Soil Test or Tissue Test Currently, in Ontario, there is no accredited soil test for S. Other jurisdictions do offer them but use them with caution. There are many factors influencing the utility of the test and questions around consistent predictability of S responses to low soil test. Plant tissue tests are offering some insight on alfalfa from Ontario based research.

Tissue testing of alfalfa (at late-bud stage) is considered a suitable diagnostic approach for determining sulphur deficiencies. The critical level below which alfalfa is considered S deficient, and may benefit from applying sulphur, is 0.25%.

Timing of Application The plant available form of S is sulphate which is an anion and moves freely in soil solution. This fact would indicate that a spring application, most likely with N, is the preferred timing. The only exception is elemental S fall applied on forages. It will take 10 to 12 months to convert to plant available sulphate.

Method of Application The method of application may be dictated by the N application method as most economical and agronomic significant sources of sulphate S are mixtures with N such as ammonium sulphate.

Generally, broadcast and incorporated, or top-dressed in the case of wheat or possibly canola, are the main application strategies. Placing S in a starter band is also an option when higher rates of N in the starter are also being addressed.

Potassium sulphate is another source that is usually applied when potash is applied and is the single most expensive form of K and S. Foliar applications generally do not supply sufficient S, the exception may be to apply foliar S to canola that is suffering from chronic S deficiency. Foliar application on wheat has not been successful.

Atmospheric Deposition of Sulphur Over the past 30 years, there has been a significant reduction in wet deposition of sulphur from rainfall. This is mostly attributed to efforts to reduce industrial discharge of sulphur compounds into the air from large industrial emitters and removal of S from diesel fuel. The result is less sulphur being added to the soil and the beginning of observations and evidence to support the need to supplement crops with S for optimum yields. The graphic on the next page illustrates the reduction in deposition of sulphate sulphur in our region from 40kg/ha in 1990 to less than 12 kg/ha in 2010. With a crop like alfalfa removing more than that amount in each cut, it is one of the reasons why we are seeing such large responses to additional S in forages.

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Changes in Annual Wet Sulfate Deposition, 1990-2010

1990 Annual Wet Sulfate Deposition

2010 Annual Wet Sulfate Deposition Source: Canada-United States Air Quality Agreement Progress Report 2012, Environment and Climate Change Canada, www.ec.gc.ca , accessed April 1, 2016.

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Competency Area 6 Determining the Right Rate, Timing and Placement of Micronutrients Performance Objective 15 Discuss considerations to determine the proper rate, timing and placement of zinc based on the: a. crop type; b. cropping system; c. crop growth stage; d. soil test or tissue test; e. timing of application; f. method of application.

Micronutrient needs vary by crop type. One of the first steps is to identify the micronutrient requirements of individual crops throughout the rotation. The table on the next page illustrates response to micronutrients for some of Ontarioâ&#x20AC;&#x2122;s agronomically important crops. Crops with a high demand are most likely to be responsive to additional applications if a suitable soil test indicates a need.

Foliar application of micronutrients.

Photo courtesy of New Holland - Agriculture

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Table 4.11 Response of Crops to Micronutrient Fertilizers

alfalfa

barley clover corn edible beans oats rye soybeans wheat asparagus broccoli, cauliflower cabbage carrots, parsnips celery cucumbers lettuce onions peas peppers potatoes radishes red beets spinach sugar beets sweet corn tomatoes blueberries

Manganese low med med med high high low high high low

Boron high low med low low low low low low low

Copper high med med med low high low low high low

med

high

med

med med med high high high high med high high high high high high med low

med med high low med low low low low med high med med med med low

med med med med high high low low low med high high med med high med

Zinc low low low high high low low med low low

Molybdenum med low high low med low low med low low high

low low

med low low

med high low

high high med med low med high high med low med

med med med high med high med

Highly responsive crops often respond to micronutrient fertilizer if the micronutrient concentration in the soil is low. Medium responsive crops are less likely to respond, and low responsive crops do not usually respond even at the lowest soil micronutrient levels.

Source: Michigan State University Publication E-486. Secondary and Micronutrients for Vegetables and Field Crops, 1994.

Chart source: Soil Fertility Handbook, Publication 611, OMAFRA, 2006, p. 72.

Crop Type From the table above, you can determine the crops with a high Zinc (Zn) demand. Crops such as corn and edible beans would be crops that a grower should pay attention to regarding the need for supplemental zinc. In contrast, a crop such as wheat has a lower requirement.

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Cropping System The crops in a crop rotation will draw more on the soil zinc supply; a rotation of corn and edible beans with higher Zn demands may require a more frequent application. Zn is a nutrient that has limited mobility and could be soil applied ahead to meet crop demands in future years. A corn, soybean and wheat rotation may only require Zn supplementation for the corn. Applying Zn in a starter band is likely the most efficient way to position Zn for uptake. With limited mobility in both the soil and the plant, placing Zn in the root zone will optimize uptake.

Crop Growth Stage The demand for micronutrients is generally important in the early vegetative growth stages although recent research has demonstrated a season long uptake pattern.

Soil Test or Tissue Test There is an accredited test for Ontario using the DTPA extraction method and reporting the value as an index that is modified by soil pH. The critical index is 15; any values below would indicate a need for zinc on high demand crops.

Table 4.12 Zinc Soil Index Interpretation Zinc Soil Index1 Greater than 200

Suggested Treatments Contamination of the sample or of the field is likely.

25 to 200

Soil zinc availability is adequate for most field-grown crops.

15 to 25

Zinc availability is adequate for most field crops. If the field sampled is uneven in soil texture, pH, or erosion, some areas may respond to zinc applications.

Less than 15

Zinc is likely to be deficient and should be applied in the fertilizer.

Zinc Index = 203 + 4.5(DTPA extractable zinc in mg/L soil) - 50.7(soil pH) + 3.33(soil pH)2 1. These values are indices of zinc availability based on extractable soil zinc and soil pH. Source: Micronutrients â&#x20AC;&#x201C; Soil Diagnostics, Ontario Crop IPM, http://www.omafra.gov.on.ca/IPM/english/soil-diagnostics/micronutrients.html, accessed April 4, 2016.

When zinc is required, it may be applied to the soil, mixed in the fertilizer at rates supplying 4-14 kg/ha (3.5-12.5 lb/acre). The higher rate should be sufficient for up to three years. Not more than 4 kg/ha (3.5 lb/acre) should be banded at planting. Zinc may be applied as a foliar spray at rates supplying 60 g/100 L (0.6 lb/100 gal). A wetting agent should be added. Spray to leaf wetness.

Tissue testing can be used to determine the zinc status of plants. Assuming critical levels are available for interpretation or sample good and bad areas separately for direct comparison of values. Often a foliar application is used if the values indicate a need to supplement. Since micronutrients are needed in small amounts, foliar applications can often deliver a sufficient quantity to the right plant part (the newest growth) where deficiencies are most pronounced.

Timing of Application Timing of zinc is thought to be better in the early season as often the deficiencies can be seen as early as three to five leaf corn. Placing Zn in a starter band close to the developing roots will aid in early season uptake. Zn uptake is lower in high pH soils. Placing Zn in an acidifying band with P will enhance Zn availability.

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Method of Application As stated earlier, zinc can be either soil applied or foliar. With a proactive soil testing program and field nutrient plans, the need for zinc can be addressed early in the crop rotation and amended with soil applications. Foliar applications are best suited as a rescue treatment or used when unusual circumstances require additional applications.

Performance Objective 16 Discuss considerations to determine the proper rate, timing and placement of manganese (Mn) based on the: a. crop type; b. cropping system; c. crop growth stage; d. soil test or tissue test; e. timing of application; f. method of application.

Crop Type Similar to zinc, using Table 4.11 the demand for Mn by crop can be determined. Soybeans and wheat are two crops with high requirements for Mn as are most of the vegetable crops especially in muck soils. Rates of application can be based on a soil test. Usually, soil test recommendations will be based on a salt formulation. Divide that by eight to obtain a foliar rate. There are many foliar products available, choose the ones with the appropriate content. Many are multi-nutrient offering a shotgun approach to foliar nutrition, others are more single element based. Follow manufacturerâ&#x20AC;&#x2122;s labelled recommendations.

Cropping System Regardless of cropping system, soil applied Mn is not the most efficient method of application. The major process involved in Mn availability in the soil is oxidation reduction reactions. This process can limit plant availability, increasing when it is wet and decreasing when it is dry. Soil applications can be made but require higher rates and should be band applied in a starter fertilizer such as MAP to limit soil contact and be in the acidifying environment to keep availability high.

Crop Growth Stage Early season applications are thought to be best. If soil applying, place in bands rather than broadcast.

Most likely, a foliar application is best and may have to be repeated as new growth appears.

Insufficient leaf surface area may limit the amount of Mn taken up early in the growth stages. Soybeans may need more than one spray as deficiencies can appear based on weather conditions throughout the vegetative stages.

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Soil Test and Tissue Test There is an accredited test for Mn using the phosphoric acid extraction methodology. Soil test values are expressed as an index modified by soil pH with the critical value based on 16. Table 4.13 offers an interpretation.

Tissue tests can also be used to determine nutritional status. Most labs will offer an interpretation based on a critical level. Follow lab protocols for sample submissions.

Table 4.13 Manganese Soil Test Interpretation Manganese Index1 greater than 30

Suggested Treatments Soil manganese availability is adequate for field-grown crops.

16 to 30

Soil manganese availability is adequate for many crops but is approaching deficiency levels for oat, barley, wheat and soybeans. If deficiency symptoms appear, spray with manganese. Consider a recheck for deficiency using plant analysis.

below 16

Soil manganese availability is believed to be insufficient for oat, barley, wheat and soybeans. Spray with manganese at the 4-leaf stage and again 3 weeks later if required. Manganese deficiency has not been diagnosed on corn in Ontario, even on soils that are very deficient for wheat.

1. These values are indices of manganese availability based on extractable soil manganese and soil pH. Chart source: Agronomy Guide for Field Crops, Publication 811, OMAFRA, 2009, p. 161.

Table 4.14 Manganese Requirements Vegetable Crops Manganese Index1

Manganese (Mn) Required2 - kg/ha Onions, Lettuce, Beets

Other Vegetable Crops

0-7

2

03

8-15

2

0

16-49

0

0

50+ Above Normal

0

0

1. Manganese Index = 498 + 0.248 (phosphoric acid extractable Mn in mg/L of soil) - 137 (soil pH) + 9.64 (soil pH) 2. Manganese should be applied as foliar spray of manganese sulphate. Soil applications are inefficient.

3. The manganese soil test is low, however manganese deficiency is not expected on this crop. If deficiency symptoms appear, make a foliar application of 2 kg Mn/ha in 200 L water (1.8 lb Mn/acre in 18 gal water).

2

Source: Micronutrients, Specialty Crop Opportunities, http://www.omafra.gov.on.ca/CropOp/en/general_agronomics/nutrient_management/micronutrients.html#manganese, accessed April 4, 2016.

Timing of Application See explanation under cropping system and crop growth stage.

Method of Application See explanation under cropping system and crop growth stage.

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Performance Objective 17 Discuss considerations to determine the proper rate, timing and placement of boron (B) based on the: a. crop type; b. cropping system; c. crop growth stage; d. soil test or tissue test; e. timing of application; f. method of application.

Crop Type From Table 4.11, choose the crops with high demand for boron (B). Alfalfa, broccoli and cauliflower stand out as needing B. Canola is not in the table but current research is suggesting response to foliar B. Foliar B applications on canola can help reduce the negative impacts of high temperature during flowering. On alfalfa, a deficiency can usually be corrected or prevented by an application of 1.0-2.0 kg/ha of boron broadcast annually. Boron should not be banded at seeding. Boron application on crops that have not demonstrated a need may actually cause yield declines.

Cropping System Depending on the crop rotation, the need for B will be determined. Alfalfa has a high demand and would most likely require supplemental B especially on higher pH coarse-textured soils. Care must be taken not to over apply B and have carryover to sensitive crops following the alfalfa. Careful field nutrient planning would account for nutrient needs ahead of time and formulate an application strategy.

B on alfalfa may be best applied in the spring before dormancy breaks or just after the first cut.

Crop Growth Stage Boron is initially involved in root elongation early in the season and then becomes a sugar mover. It is involved in cell wall structures and reproduction processes later in the season. A continuous supply throughout the season, especially on vegetables, usually means multiple smaller rates of applications to meet metabolic requirements.

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Soil Test and Tissue Test Currently, there is no accredited soil test but labs do offer a hot water extractable methodology.

Interpretation is lacking. If applying foliar, follow manufacturer’s recommendations. For alfalfa B application see comment under crop type above. Tissue tests are available and will interpret nutrient status based on critical levels. See Table 4.15, any values below 20 ppm on alfalfa for B would indicate a deficiency.

Table 4.15 Interpretation of Plant Analysis for Alfalfa Nutrient

Units

Critical Concentration1

Maximum Normal Concentration2

Nitrogen (N)

%

-

5.5

Phosphorus (P)

%

0.20

0.5

Potassium (K)

%

1.70

3.5

Calcium (Ca)

%

-

4.0

Magnesium (Mg)

%

0.20

1.0

Sulphur (S)

%

0.22

-

Boron (B)

ppm

20.0

90.0

Copper (Cu)

ppm

5.0

30.0

Manganese (Mn)

ppm

20.0

100.0

Molybdenum (Mo)

ppm

0.5

5.0

Zinc (Zn)

ppm

10.0

70.0

Chart source: Agronomy Guide for Field Crops, Publication 811, OMAFRA, 2009, p. 68.

Timing of Application Boron is very soluble and mobile in the soil. Early season broadcast on alfalfa with dry granular B mixed in potash is common and an acceptable practice. Foliar B on alfalfa has limited value as the rates required are too high and the risk of foliar burn limits its appeal (no point in burning the foliage that is needed for feed value). In vegetable crops, a combination of soil applied and foliar at critical developmental stages is practiced by most growers. In apple trees, pre- or post-bloom spray, based on tissue test critical levels, suggest a rate of 200 g/ha of actual B. Method of Application Banding or seed row placed boron can be toxic to plants and is not recommended. In alfalfa, the recommendation to correct a boron deficiency is to broadcast 1 – 2 kg/ha of actual boron, applied annually. The benefit of broadcast and incorporated B in canola has not been tested in Ontario. If B is to be applied foliar in canola, the recommended rate is 0.3 – 0.5 lb/ac (0.34-0.56 kg/ha) of actual boron. Many other field crops have low B requirements and can be injured by B applications. Most notable are the grass family, dry beans, cereals, soybeans, corn, and peas. If these crops are to follow in the rotation, do not apply boron the previous fall, or exceed the recommended rate in the previous alfalfa or canola crop.

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Competency Area 7 Determining the Right Rate, Timing and Placement of Lime for pH adjustment Performance Objective 18 Discuss considerations to determine the proper rate, timing and placement of agricultural lime based on: a. target pH by crop; b. soil test pH and buffer pH, and magnesium; c. timing of application; d. method of application; e. sources of lime; f. major nutrient contribution from lime.

Soil pH is one of the most important nutrient parameters in crop production. Soil pH controls the availability of essential nutrients by influencing water solubility and therefore plant availability of nutrients. Soil pH also influences many biological activities involved in nutrient cycling.

Choosing the rate of limestone involves determining the target pH, using the BpH to determine lime rate, looking at the Mg soil test to determine type of lime, and making an application that is most effective in both timing, cropping system and depth of incorporation. And, finally, a rate adjustment based on the Ag Index.

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Table 4.16 Lime Requirements to Correct Soil Acidity Based on Soil pH and Soil Buffer pH Buffer pH1

Target Soil pH 7.0

6.52

6.03

5.54

7.0 6.9 6.8 6.7 6.6

2 (0.9) 3 (1.3) 3 (1.3) 4 (1.8) 5 (2.2

2 (0.9) 2 (0.9) 2 (0.9) 2 (0.9) 3 (1.3)

1 (0.5) 1 (0.5) 1 (0.5) 2 (0.9) 2 (0.9)

1 (0.5) 1 (0.5) 1 (0.5) 1 (0.5) 1 (0.5)

6.5 6.4 6.3 6.2 6.1

6 (2.7) 7 (3.1) 8 (3.6) 10 (4.5) 11 (4.9)

3 (1.3) 4 (1.8) 5 (2.2) 6 (2.7) 7 (3.1)

2 (0.9) 3 (1.3) 3 (1.3) 4 (1.8) 5 (2.2)

1 (0.5) 2 (0.9) 2 (0.9) 2 (0.9) 2 (0.9)

6.0 5.9 5.8 5.7 5.6

13 (5.8) 14 (6.2) 16 (7.1) 18 (8.0) 20 (8.9)

9 (4.0) 10 (4.5) 12 (5.4) 13 (5.8) 15 (6.7)

6 (2.7) 7 (3.1) 8 (3.6) 9 (4.0) 11 (4.9)

3 (1.3) 4 (1.8) 4 (1.8) 5 (2.2) 6 (2.7)

5.5 5.4 5.3 5.2 5.1

20 (8.9) 20 (8.9) 20 (8.9) 20 (8.9) 20 (8.9)

17 (7.6) 19 (8.5) 20 (8.9) 20 (8.9) 20 (8.9)

12 (5.4) 14 (6.2) 15 (6.7) 17 (7.6) 19 (8.5)

8 (3.6) 9 (4.0) 10 (4.5) 11 (4.9) 13 (5.8)

5.0 4.9 4.8 4.7 4.6

20 (8.9) 20 (8.9) 20 (8.9) 20 (8.9) 20 (8.9)

20 (8.9) 20 (8.9) 20 (8.9) 20 (8.9) 20 (8.9)

20 (8.9) 20 (8.9) 20 (8.9) 20 (8.9) 20 (8.9)

15 (6.7) 16 (7.1) 18 (8.0) 20 (8.9) 20 (8.9)

Chart source: Agronomy Guide for Field Crops, Publication 811, OMAFRA, 2009, p. 159.

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Target pH by Crop Different crops have optimum pH ranges in which they grow best. These have been established for agronomically important crops in Ontario see Table 4.17 for ranges Table 4.17 Soil pH at Which Lime is Recommended for Ontario Crops Soil pH Below Which Lime is Recommended

Crops

Target Soil pH1

Coarse and medium-textured mineral soils (sand, sandy loams, loams and silt loams) Perennial legumes, oat, barley, wheat, triticale, beans, peas, canola, flax, tomatoes, raspberries, strawberries, all other crops not listed below

6.1

6.5

Corn, soybeans, rye, grass, hay, pasture, tobacco

5.6

6.0

Potatoes

5.1

5.5

Alfalfa, cole crops, rutabagas

6.1

6.5

Other perennial legumes, oat, barley, wheat, triticale, soybeans, beans, peas, canola, flax, tomatoes, raspberries, all other crops not listed above or below

5.6

6.0

Corn, rye, grass hay, pasture

5.1

5.5

5.1

5.5

Fine-textured mineral soils (clays and clay loams)

Organic soils (peats and mucks) All field and vegetable crops

1. Where a crop is grown in rotation with other crops requiring a higher pH (for example, corn in rotation with wheat or alfalfa), lime the soil to the higher pH. Chart source: Agronomy Guide for Field Crops, Publication 811, OMAFRA, 2009, p. 158.

Soil Test pH and Buffer pH Soil pH controls the availability of essential nutrients. The flowing graphic illustrates the range of availability influenced by the pH. The area of each nutrient in the bar graph at its widest point is the area of maximum availability.

Source: Spectrum Analytic, http://www.spectrumanalytic.com/doc/library/articles/soil_buffer_ph, accessed April 21, 2016

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As an example, in phosphorus we can see from the graph the bar narrows at pH below 6.5 and again at pH 7.5. The ideal pH for all nutrients is 6.8 as a vertical line from 6.8 will intersect most nutrients at the widest part of the bar graph.

Muck soils will tend to have optimum nutrient availability at pH 5.5. These soils exhibit very high CEC and can hold high amounts of exchangeable cations, mainly calcium, and still be 50% saturated with hydrogen. Muck soils are derived from decaying plant matter with organic matter usually greater than 50%. They lack the mineral content that can provide aluminum, one of the major contributors to soil acidity that increases phyto-toxicity to roots. As a result, vegetable crops can grow under lower pH and still find ample calcium and experience no deleterious effects of aluminum. Seldom is there a need to lime muck soils.

Soil pH measures active acidity whereas Buffer pH measures reserve acidity. Both values are determined by a lab test. Magnesium soil value is used to determine which kind of limestone to use.

Two types of limestone are available in Ontario; dolomitic which contains Mg as well as Ca and calcitic lime that contains predominately calcium. Dolomitic is chosen when the soil test is below 100 ppm to supply additional Mg. This is often the most cost effective way to increase soil test Mg and reduce acidity Timing of Application Timing of application is often determined by the most sensitive crop in the rotation, the limestone quality or Ag Index, and the time needed to make an effective pH change. Usually a fall application is done when there is more time for that task. After winter wheat harvest is usually an effective time to sample and apply limestone. Soil testing can be done with ample time to allow turnaround time from soil test lab, view results, make a field nutrient plan, source the appropriate lime and apply.

Method of Application For lime to be effective, it needs to be broadcast applied and thoroughly incorporated into the bulk of the soil so the reaction can take place to neutralize the acidity. This often means plowing and incorporating into the root zone. In no till, this may require a one-time tillage operation. Applying half the rate twice as often has been another practice that producers have adopted in no till or minimum till systems. It may mean a slower rate of reaction or in some cases near surface acidity is all that needs to be corrected. Banding of limestone is not effective.

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PROFICIENCY AREA IV - Potassium, Secondary Macronutrients and Micronutrients

Sources of Lime There are two main sources of limestone, calcitic and dolomitic. They can vary in quality. To evaluate quality, an Ag Index is used to provide a combined measure of neutralizing value and fineness rating into one value. The final adjustments to recommended rates are made with the Ag Index. Most labs assume an Ag Index 75 lime will be used when offering a limestone recommendation. Based on lime source and quality, an adjustment to the final recommended rate may be required to account for neutralizing differences in sources.

There are other source materials that can be used such as wood ash and other industrial by-products or other mineral deposits. They do need a lab test to determine neutralizing value to allow for rate adjustments with an Ag Index. These materials may contain other nutrients and sometimes undesirable heavy metals. When a non-traditional material comes to market, always perform a lab test. Note that gypsum is an ineffective lime source; it has no neutralizing value but can supply calcium and sulphur.

Table 4.18 Calcium Sources Formula

Neutralizing value relative to calcium carbonate

Calcitic lime (calcium carbonate)

CaCO3

100

Magnesium carbonate

MgCO3

119

Dolomitic lime (calcium magnesium carbonate)

CaMg(CO3)2

109

Calcium hydroxide

Ca(OH)2

135

Calcium oxide

CaO

179

Magnesium hydroxide

Mg(OH)2

172

Magnesium oxide

MgO

250

Potassium hydroxide

KOH

90

Gypsum (Calcium sulphate)

CaSO4â&#x20AC;˘2H2O

0

Wood Ashes

n/a

40-80

Chart source: Soil Fertility Handbook, Publication 611, OMAFRA, 2006, p. 89.

Table 4.19 Example Calculation of Fineness Rating of a Limestone Particle Size Coarser than No.10 sieve No.10 to No. 60 sieve

1

2

Passing through No. 60 sieve

% of Sample

Fineness Factor

10

x0

=0

40

x 0.4

= 16

50

x 1.0

= 50

Fineness Rating

= 66

1. A #10 Tyler sieve has wires spaced 2.0 mm apart.

2. A #60 Tyler sieve has wires spaced 0.25 mm apart.

Chart source: Agronomy Guide for Field Crops, Publication 811, OMAFRA, 2009, p. 159.

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The Agricultural Index This index has been developed in Ontario as a means of combining the neutralizing value and the fineness rating to compare various limestones that are available.

The Agricultural Index = (neutralizing value x fineness rating) รท 100 The Agricultural Index can be used to compare the relative value of different limestones for neutralization of soil acidity. Lime with a high Agricultural Index is worth proportionately more than lime with a low index because it may be applied at a lower rate.

For example, if two ground limestones, A and B, have Agricultural Indices of 50 and 80 respectively, the rate of application of limestone A required for a particular soil will be 80/50 x the rate required for limestone B. Limestone A spread on your farm is worth 50/80 x the price of limestone B per tonne.

Recommendations from the OMAFRA soil test service are based on limestone with an Agricultural Index of 75. If the Agricultural Index is known, a rate of application specifically for limestone of that quality can be calculated. This can be done using the following equation: Limestone application rate from soil text x (75 รท Agricultural Index of Limestone) = Rate of Application of Limestone For example, if there is a limestone requirement by soil test of 9 t/ha, and the most suitable source of limestone from a quality and price standpoint has an Agricultural Index of 90, then apply 7.5 t/ha (75/90 x 9).

The Agricultural Index does not provide information about magnesium content. Dolomitic limestone should be used on soils low in magnesium.

Tillage Depth Lime recommendations presented here should raise the pH of the top 15 cm (6 in) of a soil to the listed target pH. If the soil is plowed to a lesser or greater depth than 15 cm, proportionately more or less lime is required to reach the same target pH. Where reduced tillage depths are used, reduce rates of application proportionately. More frequent liming will be needed Major Nutrient Contribution from Lime The two main nutrients that come from lime are calcium from calcitic limestone and calcium and magnesium in dolomitic lime. These nutrients are readily available from lime when it reacts in acidic conditions. Limestone reacts in the presence of hydrogen ions. The accompanying carbonates or hydroxyl ions do the work of neutralizing acidity by removing H ions and then the calcium and magnesium can re-saturate the exchange complex.

Calcitic lime usually contains calcium in the range of 35% to 39%; there may be up to 2% of Mg in some sources.

Dolomitic lime can contain Ca in a range of 19% to 21% and Mg from 9% to 13%.

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PROFICIENCY AREA V

MANURE MANAGEMENT Competency Area 1 Whole-Herd or Whole-Flock Total Annual Manure and Nutrient Production Performance Objective 1 Calculate the total number of nutrient units in an operation.

In Regulation 267/03 under the Nutrient Management Act, 2002, a nutrient unit is defined as “the amount of nutrients that give the fertilizer replacement value of the lower of 43 kg of nitrogen or 55 kg of phosphate as nutrient as established by reference to the Nutrient Management Protocol”. Nutrient units are calculated by looking at Table 1 in the Nutrient Management Tables. It lists various species and sizes of animals, and the number of each it takes to generate one NU. The complete tables can be found at http://www.omafra.gov.on.ca/english/nm/regs/nmpro/nmtab01-15.htm. If the farm unit has more than one type of farm animal present on it then this calculation would have to be completed for each type of animal separately, then all the results totaled to give the total NU generated by farm animals on the farm.

Below are two excerpts from Table 1 from the Nutrient Management Tables, mentioned in the above paragraph, as examples.

Table 5.1. Excerpts from Table 1 in the Nutrient Management Tables Beef - Backgrounders (7 - 12.5 months) Sub Sub-Type

Ave. Weight (kg)

Utilization (%)

Liquid Amt (m3 1000 kg/day)

Liquid DM* (%)

Solid Amt (m3 1000 kg/day)

Solid DM* (%)

Nutrient Units (animal/NU)

Livestock Housing Capacity (m2 animal)

Confinement

308

90

0.0724

9.0

0.0604

22

3

4.65

Yard/Barn

308

90

0.0604

22

3

3.72

Horses – Medium Frame (including unweaned offspring) Sub Sub-Type

Ave. Weight (kg)

Utilization (%)

Box Stalls

454

100

Liquid Amt (m3 1000 kg/day)

Liquid DM* (%)

Solid Amt (m3 1000 kg/day)

Solid DM* (%)

Nutrient Units (animal/NU)

Livestock Housing Capacity (m2 animal)

9

0.0887

46

1

23.2

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Calculation example for a farm with 120 beef backgrounders and 10 horses: Livestock

Nutrient unit conversion factor (from Table 1 in the NM Tables)

Nutrient Units

120 beef backgrounders

3

40

10 medium frame horses

1

10

Total Nutrient Units

50

Performance Objective 2 Distinguish the difference between animal units and nutrient units.

As noted in the Performance Objective above, a nutrient unit is defined under the Nutrient Management Act 2002 as “the amount of nutrients that give the fertilizer replacement value of the lower of 43 kg of nitrogen or 55 kg of phosphate as nutrient as established by reference to the Nutrient Management Protocol”.

In other jurisdictions, including the U.S., they use the term “animal unit” when conducting nutrient management plans. The animal unit factor is determined by dividing the average mature animal weight by 1,000, so one AU is the equivalent of 1,000 pounds animal live weight. Individual regulations and legislation will have prepared tables listing the standard unit of measurement for typical animal feeding operations. Below is an example from the Illinois Livestock Management Facilities Act: Sec.10.10. “Animal unit” means a unit of measurement for any animal feeding operation calculated as follows: 1. Brood cows and slaughter and feeder cattle multiplied by 1.0.

2. Milking dairy cows multiplied by 1.4.

3. Young dairy stock multiplied by 0.6.

4. Swine weighing over 55 pounds multiplied by 0.4.

5. Swine weighing under 55 pounds multiplied by 0.03.

6. Sheep, lambs, or goats multiplied by 0.1.

7. Horses multiplied by 2.0.

8. Turkeys multiplied by 0.02.

9. Laying hens or broilers multiplied by 0.01 (if the facility has continuous overflow watering).

10. Laying hens or broilers multiplied by 0.03 (if the facility has a liquid manure handling system).

11. Ducks multiplied by 0.02.

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Performance Objective 3 Discuss the use of NMAN software to calculate the total amount of manure produced in a year by an operation.

NMAN is a software tool, developed by OMAFRA, you can use to determine the best way to store, treat and use materials, such as manure, on your farm. NMAN is organized in a series of linked sections called worksheets. The MSTOR worksheet in the program will help you to estimate the volume of manure generated on a farm and the resulting amount of storage needed. This worksheet allows you to include other materials, such as milking centre wash water, silo seepage and treatments such as anaerobic digesters.

NMAN uses basic information about manure production from the Nutrient Management Tables but also adjusts the values based on inputs including livestock weight, bedding amount and dry matter content of the manure, if the user enters other than the default values. NMAN can also override the manure type produced, if desired.

For instance, based on the Table 1 excerpts under P.O. 1, 120 beef backgrounders in a confinement system at an average weight of 308kg and 90% utilization will produce approximately 733 m3 per year: 120 cattle * 0.90 utilization * 308kg /1000kg * 0.0604 m3 1000kg/day * 365 days/year = 733 m3 Additional details regarding NMAN can be found on the OMAFRA website: http://www.omafra.gov.on.ca/english/nm/nman/agrisuite.htm

Performance Objective 4 Discuss why it is necessary to build up a set of manure nutrient tests in order to develop reliable average values for a particular operation that can eventually be substituted for published values.

Fertilizer adjustments based on a manure analysis will be more accurate than those based on average values. Manure analysis is necessary because the quantities of nutrients contained in manure will vary from farm to farm, especially the phosphorus and potash components. The type of livestock, feeding ration, bedding, added liquids and storage system all affect the final nutrient analysis. Phosphorus tends to be concentrated in the solids, while potassium levels tend to be higher in the liquid portion, therefore the level of agitation will affect nutrient levels being applied to a field.

Even within the same farm, manure is inherently variable depending on the growth stage of the animals, changes in rations, amount of dilution, etc. Grab samples represent a snapshot of the manure within the storage. Depending on how variable the manure is and how carefully the sample is homogenized before sub-sampling, they will vary from one sampling period to the next.

As more samples are collected, an average value will emerge that reflects the most likely value for the manure in storage. For even greater accuracy, you can segregate the samples from different sampling periods. For example, you could group all of the spring samples together and all the fall samples in a different group. The averages would reflect the differences in feeding regimes and dilution of the manure.

PROFICIENCY AREA V - Manure Management

151

Performance Objective 5 Calculate the total nitrogen, phosphorus and potassium in the manure produced by an operation in a year using published or test values of manure nutrients.

Total yearly nutrient production for an operation can be calculated by assessing the nutrient content in a given volume of manure and then multiplying that amount by the total estimated manure production on the operation. Nutrient content of manure can be estimated from the manure databank in NMAN or from the summary chart shown in Table 5.2 (below). The nutrient content of manure can also be determined by laboratory analysis of a representative sample, which is the preferred method to ensure the most accurate nutrient values are used.

In the example shown for Performance Objective 3, NMAN calculates that the 733m3 of manure produced yearly by 120 beef backgrounders has a fresh mass of 631 tonnes. Table 5.2 gives an average total N concentration of 0.73% for solid beef manure. Therefore the beef backgrounders on the operation produce about 4.6 tonnes of total nitrogen in their manure. Note that using NMAN in this scenario would be preferable to Table 5.2 as it would adjust values for dry matter percentage and other factors.

Table 5.2. Average Nutrient Analysis of Livestock Manures

Manure Type

Swine

Poultry

Dairy

Beef

Sheep Horses

(# of Samples) Liquid (924) Solid (54) Liquid (137) Solid (623) Liquid (860) Solid (150) Liquid (81) Solid (176) Solid (54) Solid (32)

Dry Matter %

Total N1

NH4-N

P2

K

Ca

Mg

Fresh Weight Basis % %

S

Zn

Cu

Mn

%

ppm

ppm

ppm

%

%

%

%

3.8

0.40

0.265

0.13

0.17

0.12

0.06

0.06

85

30

22

29.8

0.90

0.258

0.47

0.56

-

-

0.14

172

103

-

10.6

0.83

0.558

0.3

0.3

1.6

0.08

0.08

70

11

64

52.6

2.37

0.550

1.11

1.17

4.6

0.28

0.16

238

33

204

8.5

0.36

0.153

0.09

0.24

0.49

0.14

0.04

48

17

40

24.2

0.61

0.128

0.17

0.50

1.54

0.36

0.08

95

29

107

7.95

0.52

0.179

0.13

0.43

0.7

0.3

0.04

57

14

61

28.6

0.73

0.101

0.23

0.57

1.5

0.41

0.09

129

36

112

31.3

0.76

0.186

0.27

0.7

1.5

0.38

n/a3

170

20

140

33.41

0.42

0.068

0.13

0.36

1.7

0.56

n/a3

73

23

113

Data from manure analysis provided from Ontario Labs collected between 1992 and 2004. Micro nutrient data is obtained from a smaller subset of data. Micronutrient concentration is highly dependent on animal diet, so will vary widely between farms.

1 Total N = Ammonium-N + Organic N 2 %P = total phosphorus 3 n/a = data not available Chart source: Soil Fertility Handbook, Publication 611, 2006, p.101.

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Performance Objective 6 Use record keeping to measure the total manure produced by an operation in a year.

In addition to the standard financial and production records, it is important to keep track of the manure production on the farm. It will allow validation of estimated application rates, provide better accounting for nutrient credits from applied manure (when combined with manure analysis), and provide early warning of leaks from storage.

Manure Sample Ready to Submit to Lab. Courtesy Christine Brown There are several Tables provided in this chapter that illustrate the standard nutrient analyses of manure, how to calculate the available nutrients, and what constitutes a nutrient unit. Other information that should be documented includes: • manure test analysis if available; • the type and age/stage of production of livestock/poultry; • field identification for application (where, when and how much manure applied); • method of application; • commercial fertilizer applied; • soil and weather conditions at time of application; • crop grown; • crop yield; • soil test data; and, • volume of any manure that was sold.

Taking a Manure Sample. Courtesy Christine Brown

PROFICIENCY AREA V - Manure Management

153

Competency Area 2 Adequacy of the Land Base for Applying Manure Performance Objective 7 Use the Phosphorus Index to assess the risk of loss of phosphorus from a field and how it may exclude some fields from receiving manure and/or require setbacks.

The Phosphorus Index is an indicator of the risk of surface water enrichment with P from runoff. It takes into account proximity to water, land management and erosion potential as well as P soil test and fertilization to assess risk.

The P Index considers many factors, such as the conditions of a field (phosphorus levels in the soil, soil erosion and soil runoff risk), the quantity of nutrients to be applied along with their methods of application, and the distance to the nearest surface water.

The P Index assigns a number - 0, 1, 2, 4, 8 or 16 - to each of the conditions which can affect phosphorus losses, where 0 is the lowest P loss potential and 16 is the highest P loss potential. This is completed according to the probability of P loss from the site. Furthermore, each site characteristic is assigned a weighting factor that indicates the seriousness of the P loss potential of that individual site characteristic. All of the weighted conditions are added together to obtain the P Index.

Current agricultural nutrient management best management practices indicate that a Phosphorus Index should be determined if the P soil test for a particular field is above 30 ppm. A Phosphorus Index can still be calculated if the P soil test is below 30 ppm if the farmer feels it is necessary for management information.

The P Index can impact a nutrient management plan in two separate ways: â&#x20AC;˘ Sets minimum separation distances for nutrient application close to surface water. â&#x20AC;˘ Determines maximum phosphorus application rates in vicinity of surface water.

See also Proficiency Area 3: Phosphorus, Performance Objective 21. For details on calculating a P Index, refer to OMAFRA Factsheet 05-067, Determining the Phosphorus Index for a Field, August 2015.

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Performance Objective 8 Evaluate the adequacy of the cropland available for spreading manure by comparing the total annual manure production to the land base.

A number of factors must be considered in order to determine the land base capacity to safely receive manure. The first step should be to calculate the total N and P generated on the farm (see P.O. 5).

Second, calculate the total land area available to receive nutrients (total farmland minus setback areas laid out in factor 4 below). Calculate the total nutrient requirements of the crops grown on that land and the total crop removal. If the manure N or P is greater than the largest of these (requirements or removal) then there is excess manure.

The OMAFRA computer software program NMAN and corresponding workbook (OMAFRA Publication 818) are tools that help farmers determine values for each of the following factors.

Factor 1: Nutrient Value of Manure to be Applied The nutrient value of manure varies greatly from one operation to the next. The best way to determine the nutrient value is to have it analyzed by an accredited lab for N, P and K and dry matter content.

Take liquid manure samples from an agitated tank to obtain an accurate estimate of nutrients. For a representative solid manure sample, take samples from several locations of a pile. Average manure nutrient concentrations for a range of livestock types are found in NMAN. Alternatively, you can create a rough estimation of the nutrient value of the manure produced by calculating the total Nutrient Units being generated on the farm based on livestock numbers (see Table 5.3). The total Nutrient Units will give you an estimation of the fertilizer replacement value for both N and P. Note that this method will yield less accurate values than testing the manure.

Table 5.3. Nutrient Unit (NU*) Designations for a Variety of Different Animal Types Type of Livestock

# animals per NU

Large frame dairy cow

0.7

Beef feeders

3

Swine- finishing pigs

6

Lamb feeders

20

Chickens- layer pullets

500

* A NU is equal to the amount of manure needed to give the fertilizer replacement value of the lower of 43 kg of N or 55 kg of P. For example, it takes the manure from 3 beef feeders to get the equivalent of 1 NU.

Factor 2: Planned Crop Rotation The nutrient requirements of crops vary from one crop to another. The nutrient requirements of the current crop rotation are calculated and then the extent to which manure can be applied to meet these requirements should be assessed.

PROFICIENCY AREA V - Manure Management

155

Factor 3: Current Soil Nutrient Levels, Soil Type, and Topography of the Land Base If soil nutrient levels are already high, nutrient additions from manure could be limited. The best way to determine the nutrient levels in the soil is to submit a soil sample for analysis. Soil type and topography can also limit the land base capacity for manure due to the higher risk of occurrence of contaminated runoff from soil with low soil infiltration and steep slopes.

Factor 4: Proximity to Watercourses or other Environmentally Sensitive Areas In order to reduce the risk of surface or well water contamination, setbacks for manure application are used. These setbacks should be considered when calculating how much land remains for manure application.

Manure Application Setbacks in Ontario • 330 ft. (100 m) from municipal wells • 50 ft. (15 m) from drilled wells (minimum depth of 20 metres and a watertight casing to a depth of 6 metres below ground level), • or 100 ft. (30 m) from any other well • 10 ft. (3 m) to 200 ft. (60 m) from the bank of surface water). This setback depends on a number of factors such as the incorporation method used, the slope near the watercourse and the P Index value.

Competency Area 3 Crediting the Nutrients in Manure for Crop Production Performance Objective 9 Use the availability factors for the nitrogen (current and previous applications), phosphorus and potassium in manure (e.g. published in Agronomy Guide for Field Crops and NMAN3).

The best way of determining the amount of each nutrient from manure is to analyze a sample.

Unfortunately, this is not always possible, as in the case of a new barn. In this case, average values will provide an estimate of the nutrients available to the crop.

Nitrogen uptake by crops is in the mineral form as either nitrate (NO3-) or ammonium (NH4+). This means the ammonium portion of the manure is immediately available to the crop while the organic nitrogen needs to be mineralized before it can be used. For optimum use of the nutrients in manure, they should be available where and when the crop can utilize them.

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Most of the phosphorus in manure is associated with the solid portion and is found in either the orthophosphate form (PO43-) or in readily degraded organic compounds. This means that, chemically, the phosphorus in manure does not differ greatly from the phosphorus in fertilizer. Despite this, phosphorus from manure is assumed to be less available than fertilizer to crops in the year of application. In Ontario, the availability of manure P, in the year of application, is assumed to be 40% that of fertilizer P. Nutrient management plans in Ontario credit 80% of the total P in the manure towards building soil fertility. Regular soil testing is the best way to track the actual build-up of soil P in individual fields.

Essentially all of the potassium in manure is in soluble forms and available to crops.

Ontario Agricultural Planning Tools Suite for Nutrient Management Planning. Courtesy Dale McComb

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Table 5.4. Typical Amounts of Available Nitrogen, Phosphate and Potash from Different Types of Organic Nutrient Sources Available N

Type

D.M.

Liquid Materials

%

Hog finisher

7.6

3.1 (30.7)

3.8 (38.2)

4.9 (49.4)

2.1 (21)

3.2 (32)

Hog weaners

3.0

1.6 (15.8)

2.0 (19.9)

2.6 (25.7)

1.3 (13)

1.7 (17)

Hog SEW

2.2

1.3 (12.5)

1.5 (14.8)

1.9 (18.9)

0.6 (5.5)

1.4 (14)

Hog dry sows

1.9

1.3 (13.0)

1.8 (18.3)

2.4 (24.1)

0.9 (9.2)

1.2 (12)

Dairy liquid ave

8.4

1.4 (14.4)

1.5 (15.4)

1.9 (19.2)

0.8 (7.7)

2.6 (26)

Dairy 10%-18%

14

2.0 (20.1)

2.0 (19.7)

2.4 (24.2)

1.3 (13)

3.4 (34)

Dairy 6%-10%

8.0

1.5 (14.8)

1.6 (16.2)

2.0 (20.2)

0.7 (6.9)

2.6 (26)

Dairy 2%-6%

4.4

1.0 (9.8)

1.2 (11.6)

1.5 (14.7)

0.5 (5.0)

2.0 (20)

Beef liquid ave

7.9

1.3 (12.7)

1.4 (13.6)

1.7 (16.9)

0.7 (7.3)

2.3 (23)

Beef 10%-18%

15

2.0 (19.7)

1.9 (19.1)

2.3 (23.3)

1.2 (12)

3.6 (36)

Beef 6%-10%

7.8

1.4 (13.5)

1.5 (14.5)

1.8 (18.2)

0.7 (7.2)

2.2 (22)

Beef 2%-6%

3.8

0.9 (8.6)

1.1 (10.6)

1.4 (13.6)

0.5 (4.5)

4.6 (16)

Runoff 0%-2%

0.7

0.2 (2.1)

0.3 (2.7)

0.4 (3.5)

0.1 (1.0)

0.9 (9.2)

Poultry liquid ave

11

4.2 (41.8)

5.0 (49.6)

6.4 (63.5)

14 (28)

16 (32)

Biosolids aerobic

2

0.5 (5.0)

0.4 (4.1)

0.4 (4.4)

0.6 (5.5)

0

Biosolids anaerobic

4.4

1.2 (11.8)

1.2 (11.8)

1.4 (13.8)

1.3 (13)

0

Type

D.M.

Available P205

Available K20

Solid Materials

%

Hog solid average

30

3.1 (6.1)

3.6 (7.2)

4.3 (8.6)

4.3 (8.5)

6.0 (12)

Dairy 18%-30%

21

1.7 (3.4)

2.1 (4.2)

2.4 (4.8)

1.5 (3.0)

5.0 (10)

Dairy 30% +

39

2.0 (3.9)

2.1 (4.1)

2.3 (4.5)

1.6 (3.1)

5.5 (11)

Beef 30% +

38

2.9 (5.7)

2.4 (4.8)

2.7 (5.3)

3.5 (6.9)

8.0 (16)

Beef 18%-30%

24

1.9 (3.8)

1.9 (3.7)

1.2 (4.2)

1.5 (3.0)

5.0 (10)

Horses average

37

1.5 (3.0)

1.4 (2.8)

1.6 (3.1)

1.4 (2.8)

4.7 (9.3)

Sheep average

34

3.2 (6.4)

3.8 (7.5)

4.5 (8.9)

2.6 (5.2)

8.4 (16.7)

Poultry layers

34

8.7 (17.4)

9.3 (18.6)

11.3 (22.5)

8 (16)

8.5 (17)

Poultry pullets

48

12.2 (24.5)

12.7 (25.3)

14.5 (28.9)

13 (25)

15 (29)

Poultry broilers

68

10.8 (21.6)

11.3 (22.5)

12.4 (24.7)

13 (25)

17 (33)

Biosolids dewatered

32

11.3 (22.6)

12.3 (25.6)

13.7 (27.3)

12 (24)

1.2 (2.4)

Fall1

Spring inject3

Available P205

Available K20

kg/1000 L (lb/1,000 gal)

Available N Fall

1

Spring2

Spring inject3 kg/tonne (lb/ton)

1. Late fall application or early application with cover crop.

2. Spring application incorporated within 24 hours.

3. Injection or immediate incorporation, assumes good coverage.

Chart source: Agronomy Guide for Field Crops, Publication 811, 2009, p.164.

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Worksheet for Calculating Available Nutrients from Spring-Applied Manure Using a Manure Analysis Keep the same units throughout the calculation. Some reports will provide ammonium-N contents in ppm (mg/kg, mg/L), while the other numbers are in percentages. The convert ppm to percentage, divide by 10,000.

Available Nitrogen1

Available Phosphate2

Available Potash2

A. Total Nitrogen

H. Total Phosphorus

K. Total Potassium

B. Ammonium-N

I. Available Phosphorus (H x 0.4)

L. Available Potassium (K x 0.9)

C. Organic N3 (A-B)

J. Available Phosphate (I x 2.29)

M. Available Potash (L x 1.2)

D. Ammonium Losses (B x factor from Table 9-10 on page 165) E. Available Ammonium (B-D)

For values in percent: To get: multiply by: kg/1,000 L 10

F. Available Organic N (C x factor for Table 9-11 on page 166) G. Total Available N (E+F)4

1. Available nitrogen is determined by subtracting the ammonia losses to the air from the ammonium-N applied and adding the mineralization from the organic N portion of the manure.

2. C alculate reductions in fertilizer phosphate and potash by determining the available portion of the total P and K in the manure (40% for phosphorus and 90% for potassium) and multiplying by a factor to convert from elemental form to the oxide form (fertilizer nutrients are expressed in the oxide form). In the year of application, 40% is available; another 40% is available in the follow year.

3. O rganic N will also give an N credit for several years after application: 10% in 2nd year, 5% in 3rd year, x 2% in 4th year.

4. To estimate the available N from summer or fall applications of manure, multiply the Total N content by the appropriate factor in Table 9-12, Estimate of Available Nitrogen from Late Summer- and Fall-Applied Manure, on page 166.

Available Nitrogen

Available Phosphate

Available Potash

A. Total Nitrogen

0.65

H. Total Phosphorus

0.2

K. Total Potassium

0.3

B. Ammonium-N

0.35

I. Available Phosphorus (0.2 x 0.4)

0.08

L. Available Potassium (0.3 x 0.9)

0.27

C. O rganic N (0.65 â&#x20AC;&#x201C; 0.35)

0.30

J. Available Phosphate (0.08 x 2.29)

0.18

M. Available Potash (0.27 x 1.2)

0.32

D. Ammonium Losses (0.35 x 0.38)

0.13

E. Available Ammonium (0.35 â&#x20AC;&#x201C; 0.13)

0.22

F. Available Organic N (0.30 x 0.20)

0.06

G. Total Available N (0.22+0.06)

0.28

Nutrients lb/1,000 gallons

28

18

32

An electronic version of this worksheet can be found in the OMAFRA NMAN software or as a spreadsheet at www.gocorn.net.

Worksheet source: Agronomy Guide for Field Crops, Publication 811, 2009, p.168.

PROFICIENCY AREA V - Manure Management

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Performance Objective 10 Describe how to credit the phosphorus and potassium in manure for the crop requirements recommended by soil tests using the nutrient recommendations of the Ontario Soil Management Research and Services Committee (OSMRSC) and how to adjust manure spreading rates accordingly for each field.

Table 5.5: Calculating Available Phosphorus and Potassium from Manure Most labs in Ontario report the amount of available P2O5 and K2O from manure, but occasionally you see a sample reported as % P and % K. If this occurs, you will have to convert the figures to match the units of the fertilizer recommendation.

Total P to available P2O5 % P x 2.29 = % total P2O5 % total P2O5 x 0.40 = % available P2O5 in application year % total P2O5 x 0.80 = % available P2O5 for soil build-up Total K to available K2O % K x 1.20 = % total K2O % total K2O x 0.90 = % available K2O Chart source: Soil Fertility Handbook, Publication 611, 2006, p.107

Table 5.6: Conversion from Percent to Units of Weight % available nutrient to unit of weight % available nutrient x 10 = kg/t % available nutrient x 20 = lb/ton % available nutrient x 10 = kg/1,000 L = kg/m3 % available nutrient x 100 = lb/1,000 gal (Imperial) Chart source: Soil Fertility Handbook, Publication 611, 2006, p.107

The long-term availability of phosphorus (P), potassium (K), magnesium, zinc or manganese from previous manure applications is best estimated by soil testing. Application of large quantities of manure over time can result in high levels of available P and K in soils.

Manure Application. Courtesy Christine Brown

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PROFICIENCY AREA V - Manure Management

Performance Objective 11 Evaluate the strengths and weaknesses of each tool listed below and the situations in which it is appropriate to use each tool: a. pre-plant soil nitrate test (PPNT); b. pre-sidedress soil nitrate test (PSNT); c. chlorophyll meter; d. post-season stalk nitrate.

Pre-plant Soil Nitrate Test (PPNT) The pre-plant test measures the amount of residual or carryover nitrate in the root zone before planting.

The pre-plant test allows farmers to adjust nitrogen applications to meet the needs of each specific field.

Cropping sequence significantly affects the amount of nitrogen in the soil available to corn. The preplant test is most useful in continuous corn, second-year corn fields, and fields with a history of manure applications.

The pre-plant test is most useful on medium- or heavy-textured soils and during years when precipitation is normal or below normal. Below normal precipitation in autumn and winter leads to higher spring pre-plant soil nitrate levels.

The pre-plant nitrate test does not measure nitrogen from manure applied or alfalfa plowed down the current spring. Therefore, the test may not reflect all the nitrogen available to first-year corn grown after alfalfa.

Only corn and spring barley have a PPNT soil test calibration.

Pre-Sidedress Soil Nitrate Test (PSNT) Sampling when the corn is 15-30 cm (6-12 in.) tall, before the application of sidedress nitrogen, has increased in popularity. This is referred to as the pre-sidedress nitrogen test (PSNT). By delaying sampling past the busy planting season, the PSNT allows more time for sampling and receiving results from the laboratory. More importantly, considerable evidence indicates that nitrogen recommendations based on this later sampling time are superior to those based on a planting time sample. This is particularly true when there are organic sources of nitrogen, such as manure or legumes, in the cropping system.

Sometimes the fertilizer recommendations based on the nitrate-nitrogen soil test need to be modified.

The nitrogen in manure or legumes applied or plowed down just before sampling will not have converted into nitrates and will not be detected by the soil test. Information will be provided with the test results on how to make appropriate adjustments.

The nitrate-nitrogen soil test has not been adequately evaluated for: â&#x20AC;˘ legumes or manure plowed down in the late summer or fall; â&#x20AC;˘ legumes in a no-till system; and, â&#x20AC;˘ soil samples taken prior to planting before the soil has warmed up significantly (i.e. in mid- to late April) In these circumstances, use the nitrate-nitrogen soil test with caution. Only corn has a PSNT calibration.

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Chlorophyll Meter Nitrogen is closely associated with leaf chlorophyll; thus, chlorophyll-meter readings of corn leaves provide information about the N status of the corn plants. The early season chlorophyll meter test consists of taking meter readings of corn leaves when plants are between the six- and eight-leaf stages (when plants are about 10 to 20 inches tall), which allows time to sidedress if necessary.

Currently, two methods exist for using the chlorophyll meter in corn. The preferred method is to establish a high-N reference plot that has been adequately fertilized with N fertilizer early in the season in each field to be tested. Readings are taken from this reference area and the rest of the field. Additional N is required for optimum corn yield if the average meter reading of the field is less than 95% of the high-N reference value.

Fields that have a history of manure application or the first year after forage legume (alfalfa, alfalfa/ grass, clover) do not require the establishment of a high-N reference plot. An alternate method is to take readings at the six-leaf stage and, if the readings are very high (>46), no sidedress N is recommended. If the readings are very low (<42), a sidedress N recommendation can be made using the meter reading and other field information. For fields where the readings fall between very high and very low, a second reading is taken a week later to determine if and how much sidedress N is needed.

Advantages of the early season chlorophyll meter test: • Chlorophyll meter readings are quick, easy, and provide instantaneous values.

• No samples need to be collected, processed, and sent to a laboratory for analysis.

• Cost of sampling involves only labor costs.

• Nitrogen recommendations are accurate (comparable to the pre-sidedress soil nitrate test).

Disadvantages of the early season chlorophyll meter test: • Initial expense is high (the meter costs about $1,500).

• Early season corn leaf chlorophyll levels are affected by hybrid characteristics and environmental stresses; therefore, for best results, establish high-N reference plots.

• This test is not applicable to fields that have received a pre-plant or an at-plant N fertilizer application beyond about 15 pounds per acre of starter N. Post-season Stalk Nitrate The post-season stalk nitrate test allows growers to conduct a “post-mortem” evaluation of the adequacy of their nitrogen program for the current growing season. The test is described as “post-mortem” because stalk samples are taken after the grain is physiologically mature. Given that this is a very late season test, the interpretation of the results offers no assistance in fine-tuning nitrogen management for the current year, but rather provides insight into N management options for coming years.

The basis for the test lies in the fact that corn plants deficient for nitrogen will usually remobilize stored N from the lower portions of the stalk and leaves to the developing grain; resulting in lower stalk nitrogen concentrations at the end of the season. Plants that take up excessive amounts of soil nitrogen (more than is needed for maximum yields) will store excessive amounts in the lower stalk sections by the end of the growing season; resulting in higher stalk nitrogen concentrations.

The stalk nitrate test is probably best suited for identifying fields/situations where soil nitrogen uptake was excessive (no yield benefit) and, thus, costly to the grower and possibly the environment. Typical situations where N uptake may be excessive include manured fields or fields following alfalfa that received additional (and possibly unnecessary) nitrogen fertilizer applications for the subsequent corn crop.

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International Plant Nutrition Institute, 4R Plant Nutrition A Manual for Improving the Management of Plant Nutrition, 2015.

McKague, K., Reid, K., Simpson, H., Environmental Impacts of Nitrogen Use in Agriculture, Ontario Ministry of Agriculture, Food and Rural Affairs, Factsheet 05-073, 2005.

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