FACE MANURE CHALLENGES BY UNDERSTANDING RISKS

Farms can mitigate the chance of runoff by avoiding application during high-risk time periods.

by Amber Radatz

The manure application challenges of previous generations were certainly different than the challenges of today. We now have equipment that can haul manure for more miles and under varying conditions. Gone are the days that the distance traveled was mostly determined by the day’s weather and whether the spreading tractor had a cab or not. Today’s challenges are often related to unreliability of the nutrient content and release, field compaction, cost, and finding the “right time” to spread manure onto the field for environmental concerns.

Answers from on-farm research

To help farmers navigate these challenges, there is Discovery Farms, a farmer-led research and outreach program of the UW-Madison Division of Extension focused on the relationship between agriculture and water quality. The Wisconsin-based program works on privately owned farms throughout the state to conduct unbiased research.

Our neighbor and close partner, Discovery Farms Minnesota, is coordinated through the Minnesota Agricultural Water Resources Center. Data collection methods from both states are compatible in order to capitalize on combining data and create a robust set of on-farm water quality data to inform farmers on topics like manure management, soil erosion risks, and other crop nutrient questions.

Managers of manure in the Upper Midwest or other seasonally frozen areas must take into account the two main runoff periods in winter (February and March) and spring (April, May, and June). Discovery Farms has worked with over 100 farmers in Wisconsin and Minnesota over the past 19 years to understand the challenges and solutions in the intersection between agriculture and water quality. Wisconsin and Minnesota farms are included in this information, which consists of 250-plus site years of data. The on-farm research data helps to show the stark differences in the risk of runoff earlier in the winter compared to later in the season.

The highest risk

Runoff is mostly likely in late winter months like February and March and spring months like April, May, and June. In November, December, and January, the average monthly surface runoff is less than 0.1 inches. However, February and March average 0.4 and 1 inches, respectively. The average monthly runoff for March is twice as high as the next closest month (June) and almost three times higher than February, April, May, and July.

There is less risk for runoff in November, December, and January, and this relates to the amount of precipitation during that time period as well as the risk of snowmelt or rain. The average date that the soil freezes is December 9, according to Discovery Farms soil temperature observations. There is rain and/or snowmelt in November, but rain or melting snow during November is more likely to infiltrate into the soil than rain or snowmelt during February and March when the soil is frozen or only partially thawed. The average thaw date is March 28.

One of the drivers of dissolved phosphorus loss in the winter is manure application, especially manure applied shortly before runoff or during late winter. Phosphorus is a valuable manure nutrient for crop production, but it is a concern for water quality as it creates algal blooms and excessive plant growth, harming the fishery and recreational resources. Manure application during February and March significantly elevated dissolved phosphorus loss when compared to manure application earlier in the winter or other times of the year. Manure application during the time period when runoff is more likely raises the risk for nutrient loss associated with runoff. Research has indicated that when manure does not have time to adhere to the soil, dissolved phosphorus loss can increase by two to four times. Applying manure onto a snowpack or shortly before the snowmelt, especially later in the season, leaves little chance that manure will make contact with the soil and a greater chance that nutrients will be lost in runoff.

Farmers must adjust

Concerns with winter spreading can be addressed if farmers understand the risks associated with varying soil conditions and consider weather forecasts prior to spreading on frozen ground. Spreading just before snowmelt or a winter rain event significantly raises the risk of manure and nutrient movement. The key to reducing nutrient loss during winter manure application is to understand the local conditions and have a detailed spreading plan in place for winter and throughout the year. Working to apply manure during a low risk time period can mean that farmers need to alter rotations or consider options that allow them to manage manure during the lowest risk time periods. Especially for farmers with stored manure, managing the storage throughout the year is the best practice to make sure there is no ‘need’ to spread when conditions are ripe for runoff.

Utilizing other tools, like the Runoff Risk Advisory Forecast in Wisconsin, allows farmers a real-time look at the runoff risk no matter the season. This forecasting tool is a joint effort by several state agencies, including Discovery Farms and other state and federal partners. Investigate the options available for your area, and work to utilize the best tools available to reduce the risk of loss from winter manure application. ■

For more information about the Discovery Farms Programs in Wisconsin and Minnesota, visit www uwdiscoveryfarms. org or www.discoveryfarmsmn.org .

The author is co-director of the University of Wisconsin-Madison Division of Extension Discovery Farms Program.

Dissolved phosphorus drives phosphorus loss on frozen soils, and late winter manure application can increase losses by two to four times compared to early winter application or no winter application. Manure application on frozen ground shortly before a snowmelt or rain drives the largest losses.

Michigan

Michigan’s Concentrated Animal Feeding Operation (CAFO) General Permit is under a routine five-year revision by the Department of Environment, Great Lakes, and Energy (EGLE). The permit, which applies to about 260 farms in the state, was last updated in 2015 and expires on April 1, 2020.

After meetings held last spring with agricultural, environmental, and local government groups, proposed updates to the pollution discharge permit for CAFOs were issued in late October. Among the more notable changes would be a ban on spreading manure in January, February, and March.

Three public hearings were held in December to address community concerns, and the public was invited to submit comments about the proposed updates prior to December 18, 2019.

develop groundwater sustainability plans (GSPs), and manage groundwater for long-term sustainability.

In the SGMA 2019 Basin Prioritization, 94 basins and/or sub-basins were identified as medium or high priority. These 94 basins, when combined with adjudicated areas that have existing governance and oversight in place, account for 98 percent of the pumping (20 million acre-feet), 83 percent of the population (25 million California residents), and 88 percent of all irrigated acres (6.7 million acres) within the state’s groundwater basins.

The California Department of Water Resources (DWR) was first directed to prioritize basins as part of the Groundwater Monitoring legislation enacted in the state’s 2009 Comprehensive Water Package. Past prioritizations were conducted in 2014 and 2015.

The state has a transportation program in place and currently hauls about 250,000 tons of manure annually to other farms. Each year, $1 million is provided to farms to subsidize the transportation, while another $400,000 is contributed by poultry companies. The study predicts more funding will needed, upwards of $3.5 million annually, to handle the additional manure that needs to be transported.

Wisconsin

The Wisconsin Department of Natural Resources (DNR) board granted the agency permission to begin drawing up manure and fertilizer restrictions for areas prone to groundwater pollution. Despite concerns from the agricultural community, the board gave the department the green light on a 5-to-1 vote in mid-December.

Maryland

California

Basin prioritization is a technical process that uses the best available data and information to classify California’s 515 groundwater basins into one of four priority categories: high, medium, low, or very low. The most recent basin prioritization was completed in December 2019.

The process of prioritizing basins is based on eight components identified in the California Water Code Section 10933(b). Each basin’s priority determines which provisions of California Statewide Groundwater Elevation Monitoring (CASGEM) and the Sustainable Groundwater Management Act (SGMA) apply to it.

The SGMA requires medium- and highpriority basins to develop groundwater sustainability agencies (GSAs),

Maryland Agriculture Secretary Joseph Bartenfelder took counsel from an advisory committee and said he saw no need to hold up a regulation restricting the use of animal manure as fertilizer. The 19-member advisory group opposed a one-year delay in restrictions being imposed in the coming year after a study by Salisbury University found the state was not prepared to deal with the excess manure that could result.

The restrictions would affect more than 1,300 farms in the state. A majority of the acres that would be impacted by the rule are on the state’s Eastern Shore where poultry manure is widely used as fertilizer.

The Phosphorus Management Tool recommendation that was adopted in 2015 restricts or prohibits the application of phosphorus on fields where runoff is a risk. Currently, about 65,000 acres on 350 farms fall under the restriction, which was applied initially to fields with the highest soil phosphorus levels. Once the phase-in period is complete on January 1, 2022, about 228,000 acres on 1,600 farms statewide will be required to comply.

The DNR released a broad outline of the restrictions last fall. These restrictions would be similar to those already in place in 15 northeastern Wisconsin counties as a result of drinking water contamination in the state’s Kewaunee County that has significant land masses with karst topography. The proposal would impose these regulations for manure and fertilizer in yet to be defined sensitive areas with highly permeable soil in other parts of the state.

It may be months before the department completes a draft, and the final regulations would need legislative approval.

Spain

Manure was used in a protest outside of a United Nations’ (UN) Climate Change Conference in Madrid, Spain. Activists dumped a load of horse manure outside the meeting location to demonstrate their frustration with world leaders over global warming.