Organic Farmer - October/November 2018

October/November 2018 Developing High—Value Varieties of Bean for Organic Agriculture Nutrient Management in Organic Vineyards Organic Growing on the Ideal Soil Hedgerow Dynamics: Creating Beneficial Habitat

NOVEMBER 2, 2018

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IN THIS ISSUE

4

Developing High—Value Varieties of Bean for Organic Agriculture

4

CONTRIBUTING WRITERS & INDUSTRY SUPPORT Neal Kinsey

Contributing Writer

RexDufour NCAT

12

Nutrient Management in Organic Vineyards

22

Organic Growing on the Ideal Soil

Richard Smith

Vegetable Crops Farm Advisor, Monterey County, CA

Steve Vasquez

Sun World International, Director of Agronomy

Travis Parker, PhD

Candidate in the plant biology graduate group with UC Davis

UC COOPERATIVE EXTENSION ADVISORY BOARD

12 26

Hedgerow Dynamics: Creating Beneficial Habitat

32

Organic Soil Fertility for Cool Season Vegetables

32

October/November 2018

Kevin Day

Steven Koike

County Director and Director, TriCal UCCE Pomology Farm Diagnostics Advisor, Tulare/Kings County Emily J. Symmes UCCE IPM Advisor, Sacramento Valley David Doll UCCE Farm Advisor, Merced County Kris Tollerup UCCE Integrated Pest Management Advisor, Dr. Brent Holtz Parlier, CA County Director and UCCE Pomology Farm Advisor, San Joaquin County

The articles, research, industry updates, company profiles, and advertisements in this publication are the professional opinions of writers and advertisers. Organic Farmer does not assume any responsibility for the opinions given in the publication.

www.organicfarmermag.com

3

Developing

HIGH—VALUE VARIETIES of Bean for

Organic Agriculture

The Need for Crops Bred for Organic Systems

H

ow do we develop crops that meet the needs of consumers and sustainable farmers?

F

or much of the last hundred years, plant breeders have diligently improved many traits in the crops we depend on. Unfortunately, most of these crops have been selected for optimal conditions in high-input farming conditions.

In the process, the needs of organic farmers and consumers have been largely ignored. It has been estimated that 95 percent of organically-grown crops were bred in high-input conventional environments, and that this limitation is responsible for most of the yield gap between organic and conventional farms. Over the last several years, we have made considerable progress towards developing crops that are bred specifically to satisfy consumer demands and maximize organic farm profitability.

By: Travis Parker, PhD candidate in the plant biology graduate group with UC Davis

Meeting the Demands of Organic Growers

The UAV is a DJI Matrice 100 carrying RGB and multispectral cameras. The multispectral camera can detect reflectance in the infrared, which allows researchers to determine more about the plants than can be visually seen. All photos courtesy of Travis Parker.

A new crop variety absolutely has to meet the needs of farmers. Early in this project, we surveyed a group of organic growers about improvements they wanted in several major crops. These growers consistently expressed interest in high product quality, high yield, and disease resistance. They also sought varieties that would grow rapidly in the early part of the season, shading out weeds and reducing labor costs. These varieties would then transition effectively into reproductive growth, leading to high yields of a high-value product. These priorities form the foundation of our breeding and research projects.

A Focus on Dry Beans

Organic farmers are very familiar with the need for crop rotation. University of California (UC) Davis is currently working on improving varieties of peppers, tomatoes, small grains, and dry beans. Since 2015, I have been the team lead for the group working on common

4

bean, a species that includes pinto beans, black beans, and kidney beans.

As legumes, these are valued for their symbioses with bacteria, which allow them to convert atmospheric nitrogen into a biologically useful form.

No other crop family carries out this process so widely and so efficiently. Dry beans are also useful because of their relatively long shelf life. Additionally, several older ‘heirloom’ varieties of dry bean are renowned for their aesthetic and culinary quality. Growers can sell these directly to professional chefs and home cooks, sometimes earning tenfold higher revenue per pound than what is typical for major commercial market classes.

Unfortunately, these high-value heirloom varieties are not without their faults. Because they have been neglected by plant breeders, they tend to have problems that are uncommon in modern varieties. In common bean, heirloom varieties are often susceptible to bean common mosaic virus. This virus stunts growth, distorts and discolors leaves, delays maturity, and typically reduces total yields. Heirloom varieties also frequently exhibit an undesirable viny growth habit. This characteristic interferes with weed control and puts pods at risk of rotting on the soil surface. Many heirloom varieties also have low and inconsistent yields. Fortunately, these problems can all be addressed through careful plant breeding.

The black and white beans are actually cowpeas, the same species as black-eyed peas. They are also in the legume family, but are not the same species as the rest. They are of interest due to their extreme drought tolerance.

for Biological Controls , N .O . W., ia r a n r e lt A , se o n Anthrac and more .. .

The Promise of Plant Breeding Traditional plant breeding has occurred for thousands of years. In this process, cross-pollinations bring together combinations of genetic variation that never previously existed, and humans select the progeny they find most useful.

In the distant past, this process allowed humans to make domesticated crops out of wild plants that would be inedible by modern standards. Today, plant breeders can make cross-pollinations between parents with distinct sets of advantages, and select offspring that combine the desired characteristics from both parents.

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Continued from Page 5 In 2013, a collaboration began between the Gepts lab at UC Davis, which focuses on legume genetics, and Lundberg Family Farms, a company that produces sustainably-grown rice products. Lundberg Family Farms was interested in including high-value dry beans to their crop rotation, and a collaborative variety trial began the same year. By 2014, a breeding program had begun to combine the best qualities of the heirloom and commercial varieties. In its simplest form, the breeding program has proceeded by cross-pollinating promising heirloom varieties with high-yielding, upright, virus-resistant varieties developed by UC Davis and other universities. With each generation, the plants are challenged by inoculating with viruses to determine whether they have inherited the virus resistance. Only plants that are resistant to the virus are kept in the breeding program. Similarly, only progeny that show the desired seed color patterns from their heirloom parents are maintained. After several generations, the promising offspring are grown in the field to evaluate their growth habit, yield, and eventually flavor.

Field selections have occurred since 2016.

Another branch of the breeding program has sought to create a virus-resistant variety that is otherwise extremely similar to heirloom types. These lineages are nearly certain to have the cooking quality that will bring a high market price. In this branch of the project, the virus-resistant progeny are cross-pollinated back to the heirloom variety many times, allowing a breeder to naturally “dilute” a beneficial characteristic into a variety with the undesirable variant. In this breeding program, the process has been repeated up to five times, and approximately 98.6 percent of the ancestry of these lineages is derived from the heirloom parent. Almost all the plants’ characteristics are indistinguishable from the heirloom types, but the plants have no susceptibility to virus because of the strong selection.

sUAS in Plant Improvement Vigorous early season growth rate is incredibly important. Plants that grow rapidly in the initial phase of the growing season are better able to outcompete weeds, leading to reduced labor bills for growers. Despite this, breeders have had difficulty improving the trait because the genetic factors influencing it are unclear. Studying early season growth rate requires highly precise measurements across hundreds of crop varieties, often with a total population numbering in the hundreds of thousands.

The process is typically then repeated several times throughout the season. Traditionally, this was done through subjective scoring or hand-held imagery on a plot-by-plot basis, but technological advances have entirely transformed the process. Beginning in 2016, small unmanned aerial systems (sUAS) have been used in the Gepts lab at UC Davis to evaluate growth rate across hundreds of varieties of common bean. Preliminary results indicate that genes on chromosomes 1 and 3 may contribute to the trait, and this knowledge can be used by breeders to improve early season vigor in new varieties. sUAS equipped with true color (RGB), multispectral, and thermal cameras have also been useful for determining canopy height, health, and water use throughout the season. This may be useful in yield forecasting, which would be beneficial for growers and plant breeders alike.

Current Progress Preliminary results indicate that the

The brightly colored beans are all members of the breeding population.

These are less common varieties of common bean, a species that includes black beans, pinto beans, and kidney beans.

Continued on Page 8

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Continued from Page 6

Travis Parker.

breeding lines in this program are much higher yielding than the comparable heirloom varieties, while maintaining the desired seed characteristics. The breeding lineages average more than double the yield of the comparable heirlooms. All are virus resistant. Greenhouse selections for virus resistance were made as early as 2015, while field selections began in 2016. Since then, we have conducted annual field evaluation of hundreds of breeding lines, and characterized virus infection, growth habit, seed color, and yield. The most promising were selected for continuation in the breeding program. In 2018, we planted a head-to-head challenge between five heirloom varieties, ten breeding lines, and three high-yielding commercial varieties as controls. Each of these were planted out three times at

each of three field sites across California. During the season, sUAS were used to precisely determine growth rate and canopy health. This level of precision would have been nearly impossible just a decade ago. Plants were again evaluated based on virus infection and growth habit, seed color color and yield.

In autumn, a panel of chefs will do a back-to-back flavor evaluation of the heirloom varieties and the new breeding lines, and the event will be televised on a local San Diego television program.

Released varieties are expected to have the high cooking quality demanded of a high-value variety, in addition to the other traits of interest.

Project Outlook We plan to openly release 5-10 new varieties to organic growers in the next two to three years. Our preliminary data suggest that these will be considerably higher yielding than existing varieties.

Additionally, our genetic work will give breeders an understanding of the genetic basis of early season growth rate in common bean, which could lead to the release of more weed-competitive varieties. This will be disproportionately beneficial to organic growers. We also have used the knowledge gained in the process to develop a course on UAVs in Agriculture, the first of its kind at UC Davis. This trained a new generation of undergraduates, graduate students, and even a postdoctoral researcher on the emerging technology. Further training opportunities have been conducted with members of industry and academia.

For more information on these, contact trparker@ucdavis.edu.

Acknowledgements This work has been funded through the Clif Bar Family Foundation, Lundberg Family Farms, USDA-OREI, Western SARE, and Rio del Rey Farm.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

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Nutrient Management in Organic Vineyards By: Maria Zumkeller, Sun World International, Viticulture Intern and Stephen Vasquez, Sun World International, Director of Agronomy

T

he last decade has seen a sharp increase in demand for organic produce, largely due to a major shift in consumer preference and retailers offering a diversity of organic products.

California, one of the first states to regulate organic products, has been at the forefront of this trend and has had steady growth in total State Organic Program (SOP) registrants since 2009.

In fact, in 2017 organic agriculture in California topped $2.9 billion in value, accounting for more than 40 percent of all organic production in the country (Klonsky, 2013). Although organic fruit production in California falls behind both field and vegetable crops in acreage, the number of growers is greater than both organic field and vegetable growers combined. According to the Statistical Review of California’s USDA variety, ‘Autumn King’ grafted to ‘Freedom’ rootstock. All photos courtesy of Stephen Vasquez.

12

Organic Agriculture, organic grape acreage accounted for approximately 30 percent of all organic fruit and nut production in 2012. While California organic wine and raisin grapes dominate the grape category, organic table grape production has risen each year since 2009 with sale increases of nearly 5 percent in 2016 alone (Produce Market Guide, 2018).

To become certified organic, farming operations must be certified by a United State Department of Agriculture (USDA) National Organic Program (NOP) accredited certifying agency.

Additionally, California producers must register with their County Agriculture Commissioner in the county in which their headquarters are located. Organic

registration can be completed online at the California Department of Food and Agriculture’s (CDFA) website and needs to be completed annually.

Principles of Organic Production Organic growers are often encouraged to focus their efforts on creating a self-regulating system focused on pests, diseases, and fertility to reduce or minimize external inputs. Although a daunting challenge, organic table grape production can be done but entails a lot of preparation pre-plant and annual analysis of the production system.

Restrictions on synthetically manufactured pesticides or fertilizers encourages

internal cycling and a “systems” approach to farming, which also presents the greatest challenge: a limitation on the number tools available to organic growers. For this reason, an integrated approach to farming (combining cultural, biological, and mechanical practices) is essential to producing a quality crop.

Furthermore, with fewer tools at their disposal, organic grape growers do not have the benefit of making short term decisions that might otherwise be sufficient in a conventional system.

It is also important to note that in any aspect of organic grape production the tradeoffs of practices may be more difficult to evaluate because organic systems are characterized by long term decision making (e.g. low analysis and slow release organic fertilizers that may ultimately lead to reduced fertilizer applications). The reduced flexibility in organic production undoubtedly requires a more holistic approach to farming in order to produce fruit of equal quality and quantity to conventional systems.

Supplying adequate nutrition to support well balanced vines can also be difficult in organic grape production, especially for the fresh market. Thus, understanding soil properties and how nutrients become available for grapevine assimilation in addition to how factors such as rootstock selection and viticultural practices influence nutrient uptake are of critical importance. This information combined with quantitative assessments of vine nutrient status can be extremely valuable in order to make important management decisions and is crucial to maintaining a financially sustainable commercial operation.

Established vs. New Organic Vineyards Switching from a conventional production system to organic is not as simple as changing inputs from conventional agrichemicals to organically certified materials. Established vineyards that are producing high yields with exceptional quality may not transition well due to growing conditions that are being managed with conventional agrichemicals. For example, high clay soils have the ability to tie-up potassium, making

it unavailable. In a conventional system, one solution is to use an efficient, high analysis liquid potassium fertilizer that can be applied frequently throughout the season. However, for organics, there are few high analysis liquid potassium products that would satisfy the same vineyard’s needs, especially if the vineyard is in full production. An organic grape grower would have to consider applying an organic foliar potassium product to supplement a soil applied potassium program. Fortunately, there are many organic liquid and soluble powders manufactured for foliar applications that could supplement a soil applied program but may still not satisfy a vineyard’s needs.

drive around the property will help identify weak growing areas, ponding water or other noticeable issues. If soil related, pre-plant would be the time to correct them. Backhoe pits are useful for surveying soil profiles, which may give clues about compaction, poor water penetration and other issues that will negatively impact grapevine growth.

As was mentioned in the article by Neal Kinsey (Organic Farmer June/July 2018), “You cannot manage what you cannot measure”, is a key point in that article. Soil lab analysis is one of the least expensive inputs that gives a good “measure” of what a site’s soil potential might be once grapes are planted. The number of soil samples necessary to evaluate a site will depend on several factors that include but are not limited to acreage, soil type(s), slopes, swales and valleys, etc. Additional soil samples should also be collected for identifying soil pests (i.e. nematodes) and diseases (i.e. Phytophthora). This is one scenario where pre-plant soil testing can help with decisions that will have long-term

Establishing a new organic vineyard has some benefits. Soils can be evaluated pre-plant by surveying the site, digging backhoe pits and with lab soil analysis. Knowing what was grown on a site previously can give clues about what challenges might present themselves once planted to grapevines. If planted to a perennial crop, a walk or

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Continued from Page 13 impacts on vineyard health.

Soil Quality and Fertility: Cover Cropping Focusing on grapevine nutrition and organic production, a typical approach is one that “feeds the soil”, encouraging the growth of soil micro fauna critical to organic matter decomposition. This in turn provides benefits including improved soil structure (aggregation), water penetration, erosion prevention, and nutrient availability. The concept of ecological intensification is a similar guiding principle in organic production soil management. This approach aims to enhance soil ecosystem services to reduce anthropogenic inputs, creating a system characterized by low nutrient losses and high productivity. This approach is supported by incorporating

practices that improve soil biodiversity.

Cover cropping is a fundamental production practice that has been used to enhance the soil of California vineyards with substantial benefits when the right cover crop(s) are selected and properly managed.

While there are many different cover cropping objectives, their contribution to soil fertility and vine nutrition are the most well-defined (McGourty, 2004).

Their benefits will depend on a number of factors including vineyard location, climate planting time and soil condition to name a few. Once established, cover crops will help reduce soil erosion, improve soil structure and water penetration and will encourage a more diverse microfauna. Cover crops also benefit table grape production by reducing dust that can drift into the fruiting zone;

covering fruit in dust and potentially spreading disease.

More species-specific benefits may include the addition of nitrogen (N) to the soil through legume mixes, attraction of beneficial insects and retention of local pollinators and allelopathic capabilities of cover crops whose large taproot also serves to open up the soil (e.g. mustards). It is important to evaluate cover crop needs each year in order to determine grapevine needs.

Some seasons may benefit from legumes to increase nitrogen, while other years may benefit from deep rooted mustard to help improve soil aeration.

Despite the well documented benefits of cover crops, potential drawbacks

Rootstock

Vitis Parentage

Phylloxera Resistance

Mineral Nutrition

Soil Adaptation

1103 P

berlandieri x rupestris

High

N: Med.–High P, Mg: high K, Zn: low–med

Adapted to drought and saline soils.

Freedom

1613 (solonis x Othello) x Dogridge

High

N, P, K: high Mg: med.

Zn, Mn: low

Sandy to sandy loams.

Dogridge

champinii

Med.

N, P: high K: med.

Zn: low

Very sandy, infertile.

Salt Creek (Ramsey)

champinii

High

N, P: high K: med.–high Zn, Mn: low

Sandy, infertile.

Harmony

1613 (solonis x Othello) x Dogridge

Low-med.

N: low P: med.

K: high Zn: low–med.

Sandy loams and loamy sands.

SO4 (Selection Oppenheim)

berlandieri x riparia

High

N: med.–high P, K, Zn: med. Ca, Mg: med.–high

Moist, clay soils.

5BB (Kober)

berlandieri x riparia

High

N: med.–high P, K, Zn: med. Ca, Mg: med.–high

Moist, clay soils.

5C

berlandieri x riparia

High

N: low P, K: med.

Mg: med.–high Zn: low–med.

Moist, clay soils.

Table 1. Rootstock selection chart adapted from “Wine Grape Varieties of California: Rootstock Selection”.

14

Continued on Page 16

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Continued from Page 14 include the potential for cover crops to serve as alternate host for pests and diseases their large demand for water.

Still, it is important to remember that every cover crop selection (whether a monoculture or a mix) presents its own unique set of tradeoffs. For example, winter annual grasses that require large amounts of nitrogen can also delay nitrogen availability to the vines and reduce vigor when they mature. Howev-

er, this characteristic may be used as an advantage in some vineyards to manage excessive vine vigor.

To summarize, cover cropping can provide long term benefits that when properly managed, improve soil quality and influence nutrient availability over multiple seasons. Keep in mind that the impact of cover cropping will take time and a good understanding of which mix of legumes, grasses and broadleaf covers will work best at a vineyard site

Essential Minerals For Certified Organic Farms

may not be known for several seasons.

The vineyard site, plant time, cover crop selection, etc. can impact vineyard performance. Growers should consult with their local university farm advisor or certified crop adviser (CCA) to identify the best approach for their vineyard.

Soil Quality and Fertility: Compost and Mulching When establishing a new vineyard, nutrient management begins prior to planting. Before planting, soil tests can help determine whether lime, gypsum, sulfur or other soil amendments are required. Thus, proper site selection and understanding indigenous issues are crucial to making decisions that will provide long-term benefits. Soil drainage, soil depth, and nutrient status are some of aspects that should be evaluated pre-plant, as adjustments during this period can yield the greatest return on investment. Initial soil samples should be analyzed for nutrient status (deficits or excesses), pH, cation exchange capacity, and organic matter. Growers should review lab analysis and recommendations with their local university farm advisor or CCA to determine best management practices.

Once a need for amendments has been identified, quantity and timing should be established, which will may be different for new verses established vineyards.

Timing is particularly important, as another key challenge in organic grape production is synchronizing nutrient release from organic sources with vine needs, while also avoiding over-fertilization. Additionally, because most organic certified fertilizers are classified as low analysis they contain a lower concentration of elements compared to synthetic fertilizers and release nutrients at a much slower rate. This can make correcting a nutrient deficiency difficult, particularly in older, established vines.

Floor management practices such as the addition of compost or mulching may aid in the mineralization and release of nutrients.

Compost can have many beneficial effects on the growth of grapevines and its slow release of nutrients makes it an

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ideal soil amendment given the relatively low nitrogen demand of grapes. The addition of compost as organic matter also reduces nutrient leaching, improves nutrient retention, soil structure, water retention, and infiltration. These benefits are achieved primarily through the microorganisms that aid in decomposition and nutrient mineralization.

However, just as with other fertilizer products, it is important to understand the rate of fertilizer desired and the availability of the nutrients for uptake prior to determining application rates.

The carbon to nitrogen (C:N) ratio in compost can provide a guide for nitrogen release into the soil solution. When compost material has a low C:N ratio (a lot of nitrogen) microbes release the excess nitrogen into the soil solution.

When a decomposing material has a high C:N ratio (very little nitrogen) microbes will immobilize nitrogen until the decomposition process lowers the C:N ratio. Immobilization of nitrogen for high C:N ratio organic matter

decomposition may lead to nitrogen deficiency. As a rule of thumb, if the C:N ratio is lower than 20, nitrogen will be released. If the C:N ratio is above 20, nitrogen will be immobilized until sufficient decomposition has taken place (Carroll, et al., 2016).

Most composts contain a wide range of macro and micronutrients including nitrogen, phosphorous, potassium, magnesium, boron, calcium, iron, copper, and manganese. Therefore, composts nutritional contributions should be considered when developing a fertilizer program. The type of compost to apply largely depends on what goals are to be achieved. Increasing soil organic matter is best done with a low nutrient and stable compost while soil fertility can be increased with compost that is relatively high in nutrients. Regardless of the type of compost used, it is important to have current lab analysis results highlighting its organic matter, nutrients, salt and

Continued on Page 18

Commercial grapevine nursery with different scions grafted to different rootstocks.

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Continued from Page 17 heavy metal content prior to application.

The use of straw or hay mulch in vineyard row middles is another method of increasing soil organic matter to achieve soil quality. However, it is important to monitor the effects of mulching that may lead to excessive vine vigor and poor fruit quality.

Rootstock Selection and Nutrition

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When establishing a new vineyard, one decision that will have a long-lasting impact on the successful production of high-quality grapes will be rootstock selection. Originally developed to combat soil pests, rootstocks have been an integral part of establishing and maintaining healthy vineyards. Rootstocks were first used in grape production when phylloxera, the tiny aphidlike (D. vitifoliae) insect that feeds on Vitis vinifera roots, was introduced in the late 19th century to French wine grape vineyards.

Left unchecked on V. vinifera cultivars, phylloxera will feed extensively on the roots, causing abnormal root growth and open wounds that pathogenic fungi then use to infect the root system.

Additional soil pests include nematodes, which can sometimes be more damaging than phylloxera in southern San Joaquin Valley vineyards. Using their stylet, nematodes puncture cell walls to feed on the cytoplasm and its contents. Because V. vinifera is susceptible to phylloxera and nematodes, most rootstocks do not have V. vinifera in their parentage. As a result, they do not have the same growing characteristics as cultivated wine, raisin and table grape cultivars. Our knowledge of rootstock selection for soil pests are well established but limited when selecting for viticulture characteristics (i.e. nutrition).

What we do know is helpful in selecting a rootstock and research continues with existing and newly released rootstock selections.

It has been well demonstrated that the compatibility of scion and rootstock cultivars affect vine vigor and overall performance because the rootstock

may impart differing levels of mineral nutrition on the scion.

In fact, the influence of rootstocks on scion nutrient uptake can also fluctuate; changing under different soils and environmental conditions. For this reason, there is a significant value in understanding how scion/rootstock combinations perform in different soils. Rootstocks adapted to a particular soil environment should be taken into account since factors like soil texture, depth, fertility, and chemistry will play a role in nutrient and water assimilation. Table 1 illustrates the wide array of rootstock soil adaptations, mineral nutrition qualities, and phylloxera resistance. For example, ‘Freedom’ rootstock is vigorous and imparts an increased uptake of nitrogen, phosphorous, and potassium (NPK) in sandy to sandy loam soils, which may not be experienced with a rootstock with Riparia parentage. However, a rootstock with Riparia parentage may be better suited to a heavy clay soil that remains wet for long periods of time. Growers should review the pros and cons of each rootstock prior to purchase and planting since a selection can impact the life of the vineyard and future mineral nutrition decisions.

The Value of Analysis and Monitoring In addition to routine visual inspections of vineyard blocks, quantitative assessments of vine nutrient status are also crucial in order to make responsible fertilizer decisions. Under-fertilization can adversely affect grape production and lead to poor vineyard health. Similarly, over-fertilization can result in an overly vigorous vine, increased disease pressure, and poor fruit quality. Nutrient monitoring during the current season can provide the best indication of what might be needed when compared to previous nutrient analysis records. Thus, it is important to regularly sample plant tissue in addition to having soil and irrigation water samples analyzed.

Nutrient analyses can be categorized by three main goals: general surveying, follow-up, and diagnostic. General surveying aims to produce a solid set of historical data that fertilizer rates and scheduling can then be based upon. Tissue sampling under a surveying approach should begin after the cool wet season near April-May, with bloom petiole samples taken to gauge the potential need for seasonal fertilizer applications. Follow up analyses provide information about whether the decisions from surveying have met the vine’s nutritional needs. A follow up nutrient analysis should be taken from petioles of recently matured leaves at veraison (berry softening). This analysis may be worthwhile to ensure that that certain nutrients like potassium are not deficient, since potassium is mobile and declines in the foliage during fruit ripening. The final diagnostics approach serves to pinpoint any outlying deficiencies that may arise during the growing season.

Prior to identifying a vineyard’s nutrient status and establishing an annual fertilizer program, information regarding site characteristics should be determined. As previously discussed, soil analysis can provide information about the physical, chemical and biological nature of the root zone, all of which largely

influence the overall health of the grapevine. This analysis can also provide information on what nutrients are in the soil; however, this does not indicate the amount of available nutrients for uptake by the vine. The most significant information obtained from a lab soil analysis is that related to chemical imbalances or excesses. Problems in pH, high salinity or cation imbalances (Mg:Ca:K) can be identified through soil analysis and corrected prior to vineyard establishment. Water sampling should also be conducted on a routine basis to ensure that excess nitrate does not go unaccounted for.

Tying it all Together: A Nutrient Management Plan The practices, concepts, and tradeoffs discussed in this article highlight some of the key aspects of managing the nutritional demands of organic vineyards. Although the limitation of certified organic fertilizer products reduces the flexibility that growers have in responding to nutrient deficiencies, practices that encourage soil health such as cover cropping, composting, and mulching can provide a slow and steady release of nutrients to minimize the need for fertilizer applications.

There is significant value in actions and decisions made

Continued on Page 20

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Continued from Page 19 prior to vineyard establishment including the selection of a proper rootstock for the given site. Visual assessments and soil analyses pre-plant can also help identify weak spots and provide critical information as to what amendments or fertilizers may be needed. Furthermore, soil analyses every other year that target nutrient availability and other soil chemistry issues, including salinity, are the foundation of a good fertilizer program. This information coupled with routine surveying or follow up analyses can be used to maintain a healthy vineyard whereby diagnostic sampling can be used to make site specific adjustments.

Syncing nutrient supply with demand is the cornerstone of growing quality grapes but is especially important in organic grape production. Creating a nutrient management plan that maximizes inputs, including the vineyard site and scion/rootstock combinations is paramount to producing quality grapes season after season.

References •

•

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Bender, S. Franz, Cameron Wagg, and Marcel GA van der Heijden. "An underground revolution: biodiversity and soil ecological engineering for agricultural sustainability." Trends in Ecology & Evolution 31.6 (2016): 440-452.

Bettiga, Larry J. Wine grape varieties in California. Vol. 3419. UCANR Publications, 2003.

Organic Farmer

Cover Crop.

•

Carroll, Juliet, Timothy Weigle. "2016 Organic Production and IPM Guide for Grapes." (2016).

•

Ingels, Chuck A. Cover cropping in vineyards: a grower's handbook. Vol. 3338. University of California, Agriculture and Natural Resources, 1998.

•

McGourty, Glenn. "Cover cropping systems for organically farmed vineyards."

Prac. Winery Vineyard Sep 7 (2004): 38.

•

Klonsky, Karen, and Kurt Richter. "Statistical review of California’s organic agriculture." University of California Agricultural Issues Center Publication (2013).

•

Produce Market Guide: The Packer.

2018. https://www.producemarketguide.com/produce/organic-grapes

•

Klonsky K, Tourte L. 1996. Vegetables, fruits and nuts account for 95% of

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organic sales in California. Calif Agr 50(6):9-13.https://doi.org/10.3733/ ca.v050n06p9.

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Organic farmer in Illinois initially applying needed micro-nutrients in the mid-1970's to help build the "ideal soil" for this field. All photos courtesy of Neal Kinsey.

Organic Growing on the

Ideal Soil By: Neal Kinsey | Contributing Writer

T

he Ideal soil? Does it actually exist?

Agricultural educators describe it, but no textbook used for agricultural education tells how to achieve it if a soil is not already in that ideal condition.

With all the scientific advances now available, production agriculture as taught and practiced still seems to rely on a program based on the simplest soil tests that cost very little and show almost nothing of value for correcting the real nutrient needs of the soil. Is

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it actually possible to understand and correctly measure the basic needs of each different soil and correctly supply them? Is it possible to perform such measurements and to explain what is needed in understandable terms?

And can the use of such information specifically provide the guidance needed for seriously involved organic growers to build an “ideal” soil in order to supply the very best environment and the most nutritious products from

October/November 2018

organic crop production? Yes, an ideal soil is possible, but organic farmers and growers must learn how and where to start in order to accomplish what many still believe is impossible.

The soil teems with living things from the plant roots to all that is needed to sustain the plants that grow from those roots.

Increasing Life in Soil So then how does one increase the potential for producing more abundant life in the soil?

That is one of the most asked questions in agriculture today. Yet the standard answers, even those given to organic farmers and growers, generally come up short of the true solution. Living organisms must be properly fed, and consequently, cover crops, compost and manure are generally given the greatest emphasis for soil life and health. But is that all that is required for abundant soil life? No, it is not! Though it is a requirement, food alone does not insure that we can stay alive and healthy.

We also need sufficient air and water.

This clay soil is very high in magnesium which severely restricts needed air for life in the soil.

The same is true for the soil in which plant roots and soil microbes thrive.

Too many advisors ignore these basic needs leading growers to assume just increasing the life in the soil will solve such problems.

In order to supply the needs for the crops to be grown, life in the soil needs a proper environment. All life prospers with the correct amounts of air, water and food, and soil life is no different. We need to provide the “house”—a proper topsoil environment for soil life if that life is to thrive and respond properly to accurately supply the needs of the crops to be grown there. In other words, what we know and strive to do in addition to correctly feeding the crop determines how well that environment produces the greatest amounts of nutritious food and/ or feed. As some will say, to accomplish this we need the “ideal” soil.

Ideal Soil What is the ideal soil? Do such soils actually exist? If such soils do exist how would they be recognized or determined as such? What would identify and separate them from other

Compost—use only if testing shows what it contains is needed.

soils that are not so ideal? Is that something that is even possible?

What makes up the growth medium we call soil? Soil requires at least four major parts before it can be considered to be soil. Geologists say that soil is made up of decomposed rock. This is true, but that only provides one part of the story. In this part of the process, the rock breaks down to become gravel.

The gravel further decomposes to form sand (which is considered to make up the largest particles of what is called the texture of the soil). But then a part of the sand breaks down further to form finer particles called silt. And a portion of the silt is further decomposed to form clay (the smallest particles of what is called soil texture). These three sizes (sand, silt and clay) formed from any and all kinds of decomposed rock form the texture of every soil.

So then even though every soil is composed of sand, silt and clay, there are so many types of rocks and mixtures of rocks with different types of nutrient content that can become soil, how would it ever be possible to say that only one such mixture is the ideal soil?

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Considering only the mineral make up of what is required to form just a basic soil, finding the one that is most ideal should seem far more impossible to locate than finding the proverbial needle in a haystack. And even if one could be found, would other soils made up of different mixtures from several different types of rock be just as likely to grow nutritious crops just as well?

Considering the mineral content of a soil, even though a very major part, it is just one part of what makes up the soil we need to grow the best plants. The proper amounts of air and water are also required.

Most soils are not correctly balanced in terms of containing the proper amount of air and water. Sandy soils tend to have too much air in relation to needed water for plant growth.

Such soils need a specifically higher concentration of magnesium in relation to calcium content, since magnesium is the principal element in the soil that tends to disperse soil particles and reduces the amount of air space accordingly. Clay soils tend to contain

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Continued from Page 23 too much water and not enough air for ideal plant growth. Thus clay soils need more calcium in relation to magnesium content because calcium causes soil particles to flocculate or clump together which increases soil porosity and provides more air space and just measuring the pH of the soil does not provide the needed answer.

Textbooks on soil agronomy (dealing with soils and their fertility) show the ideal soil as a pie chart containing 25 percent air, 25 percent water, 4547 percent mineral content and 3-5 percent organic matter. It is defined as the ideal soil, but when that ideal is not what you have, how do you get it? That is a question that even the most authoritative soil textbooks have failed to recognize and none have even attempted to answer properly.

Feed the Soil The key that provides the real answers has been rejected by mainline agriculture, because that key is the need to feed the soil and let the soil feed the plant. And for decades the farmers who have done this by measuring each different soils’ capacity to attract and hold nutrients and supplied them accordingly have achieved the highest returns for the least cost per unit of production. Soils vary in their ability to attract and hold nutrients for plants. Depending on their make-up, some soils can hold 10 times more of a nutrient than other soils. For comparison, if we have a cup of coffee and a ten cup coffee pot, would the amount of coffee we add be the same for both? Yet too many believe it is okay to add the same amount of compost to any soil and for some it is not enough, while for others it is too much.

However, this is not what farmers and growers are presently being told. In fact, it is continually drummed into the heads of farmers and growers that feeding the soil is too expensive and the only way to survive in agriculture is to cut costs by determining and supplying just what the plant needs and otherwise disregard the needs of the soil—which only needs to be there to hold up the plant. This is just an easy way to sell a lot more fertilizer (or compost) whether it helps the soil or not.

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This a trap that ensnares many who keep trying to figure out how to get more while continually striving to give less for it. You don’t get something for nothing. Too many so-called organic producers forget this principle. They just quit using “chemicals” and forget that soils need balanced nutrition to do their best, just as livestock and human beings do. Only by understanding and doing things in a correct manner will each farmer and grower be the true winners. The correct way is to learn to understand and use the basic sciences to determine what is best for the soil and what it must have in turn to grow the food and feed crops that will correctly sustain life.

In the 1940’s a movie was made that is still just as accurate today as it was then.

Called “The Other Side of the Fence” it is still available on-line as a DVD. In the presentation two carrots are shown that look just alike, but one is full of nutrients and the other is not. Looks can fool people, but an actual analysis can reveal the truth. And based on recent studies, it has been established that the nutrient content of the plants we grow for food today are far lower than the same ones were in the middle of the last century.

Steps to Achieving Excellent Fertility The steps for achieving excellent fertility which results in high nutrient content have been known, available and used successfully by a number of dedicated organic farmers and growers for decades. It involves a system of analysis for soil fertility testing that was developed by Dr. William Albrecht from over forty years of research spanning from the 1920’s to the 1960’s.

The program provides specific answers for the nutrient needs of each individual soil. Principally it was developed from the study of the laws of basic science— biology, physics and chemistry—which do not change. These laws always react in the same way, they don’t change the way they work when moving from one type of soil to another. Actual needs are based on the true principles of soil balance, namely, if you have too much of one nutrient in a soil, you will have too little of some other needed nutrient for growing and nourishing the plants being grown there. By understanding the guidance provided from a complete soil analysis and making the appropriate

October/November 2018

corrections as required for individually building proper fertility in each different soil the resulting outcome is both excellent nutrient quality and very high yields.

Every organic grower can economically utilize this type of testing to determine exact nutrient needs and achieve top fertility levels for all different types of soils. No matter how different the make-up of various areas where growers plan to grow crops may actually be at first, bringing them into line with what is required for growing the best crops also transforms them into the ideal soil. In other words, the ideal soil is not something you go out and find, its needs have to be measured, correctly supplied from the proper materials and maintained as such. Thus the ideal soil is one where the needs have been measured and corrected in order to accurately supply what is needed for the proper amounts of air, water and nutrients to be present there for correctly nurturing the plant. So those soils farmers and growers already have that possess the ability to grow a crop can be managed and ultimately become the “ideal” soil.

Detailed Soil Analysis Finding, using and understanding a detailed soil analysis is the most significant first step needed to begin building that ideal soil from all the different variations generally found on every property. For growing the best of whatever crop growers may choose to produce, some soils are easily corrected while others may require large amounts of effort and inputs to grow truly nutrient dense foods. Giving priority to the most limiting nutrients should be an integral part of this process. Bear in mind that once the ideal soil is achieved it will still require work and proper diligence to keep it that way. You cannot correctly manage what is not correctly measured. But there are big differences in how nutrients are measured, reported and resulting needs are interpreted by soil testing services. How is it possible to know which one should be best to utilize? Test your soil tester! That is the next topic which should be of concern to those interested in achieving the best in organic production.

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Hedgerow Dynamics:

Creating Beneficial Habitat By: Rex Dufour | Western Regional Office Director, National Center for Appropriate Technology

This hedgerow has a diversity of plant structures, flowering structures and bloom times, all of which support a broad diversity of beneficials. The ground under the hedgerows is undisturbed, providing potential nesting habitat for ground nesting native bees.

All photos courtesy of Rex Dufour, NCAT.

Why Hedgerows?

O

n most farms, humans have done a good job at simplifying the ecology of the farm in an expensive attempt to reduce damage caused by weed, disease, and insect pests. Carl Huffaker, a University of California (UC) Berkeley entomologist, noted that, “When we kill off the natural enemies of a pest, we inherit their work”. Biodiversity on our farms has been reduced through two practices: use of pesticides has reduced populations of most insects (the 4 P’s: pests, parasites, predators and pollinators) on our farms. Destruction of habitat, and subsequent lack of habitat has also had significant negative impacts. A recent German study of insect populations (Vogel, G., 2017) made an alarming finding—in just three decades, insect populations in German nature reserves have plummeted by more than 75 percent—cause unknown, but this and other dramatic declines in iconic insect populations, such as monarch butterflies on both the east and west coasts, are signals that we as a society need to invest more time and thought into creating and maintaining biodiversity on human-managed landscapes. Hedgerows, which have

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Organic Farmer

historical roots in Europe, have evolved in the western US into linear plantings along field borders, oftentimes with native perennials. They are an attempt by forward-thinking growers and land owners to bring a bit of biodiversity back into farming systems, and at the same time these plantings can serve many other purposes: • • •

• • • •

• •

Habitat, including food, cover, and corridors for terrestrial wildlife.

Enhance pollen, nectar, and nesting habitat for pollinators.

Provide food, shelter and overwintering sites for predaceous and beneficial invertebrates as a component of integrated pest management.

Intercept airborne particulate matter.

Reduce chemical drift and odor movement.

Act as a windbreak Create screens and barriers to noise and dust (reducing dust on crops can reduce severity of mite outbreaks).

Provide fruit and herbs to the farmer and farm workers.

Enhance the beauty of a farm (im-

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portant for folks doing agritourism, and for its own sake).

Dynamic Design Creating, and preserving habitat for the “good guys” should be part of the ecological evolution of all farms, ranches, and publicly-owned lands. We wouldn’t expect dairy cows to thrive where there was no food or shelter, and beneficial insects should be considered mini-livestock, with the same kinds of needs as the larger, four-legged species—food (pollen, nectar, other insects), a place to hang out and meet potential mates, and lay eggs, and maybe someplace stable to overwinter.

Hedgerow design is part science, based on observation of these plants in wild habitats and agricultural settings. The other part, is, well, art...ecological art, applying, and playing with your knowledge of the plants and the local site, taking into account what services the farmer wants out of the hedgerow. For hedgerow plantings used as borders between farms, the hedgerow designer

needs to keep in mind what their farm neighbors are likely to plant in the near future, and what kind of pesticide applications are likely for that crop.

Well-designed hedgerows can beautify an area while at the same time making it ecologically richer, and a bit more productive in the long-term. Designing hedgerows to include a variety of different bloom times, plant structures, and flower and leaf structures, provides a biodiversity refuge that has the ecological flexibility to help stabilize farm insect populations. At the same time, the biodiversity supported by hedgerows provides important food for other organisms, such as birds and bats.

The environment of the hedgerow is not static. The first year, the plants are small, a certain percentage will not make it, but most of the plants, with adequate moisture to start their first years, will make it if they’re not taken over by weeds, weed-wacker blight, or flooding. Within the first three years, you

will see which plants seem to be thriving and which plants are not, and which plants didn’t make it.

It’s not unusual to lose 15 percent, or even 20 percent of the plants due to various causes. These gaps in the hedgerow should be filled in with another planting. Because many of the native perennials do not like having wet feet (flooded conditions), I recommend planting on berms, which allows for better drainage. Drip irrigation works well for establishing hedgerows, and in many locations, can be discontinued after the first few years.

Growers must decide before planting a hedgerow how they will manage the weeds—choices for organic growers are mulches of various kinds, or weed cloth, or a lot of weeding. All practices have pros and cons with respect to labor and the use of hedgerows as habitat for ground-nesting bees, which a majority of our native bees are. Or-

Structural diversity provides some surprising aspects of habitat. The panicles of deergrass provide a convenient resting spot and ambush location for damsel flies, which feed on mosquitoes and small flies, such as spotted winged drosophila.

ganic mulches, such as wood chips, walnut shells, rice hulls, straw or compost all will eventually degrade in one to several years, providing native bee populations with added nesting habitat of undisturbed soil. Organic mulches provide a nice place for most germinating seeds of hedgerow plants to begin their growth. Weed cloth prevents hedgerow plants from spreading by seeding. However, weed cloth has the advantage in that it lasts a long time, thus reducing labor and costs of weeding, but it doesn’t allow plants like yarrow, sage, California buckwheat, and others to reseed and provide additional natural cover. Weed cloth also denies ground nesting bees a bunch of potentially prime nesting habitat on the farm—undisturbed soil. A compromise is to use two strips of weedcloth, one on either side of the hedgerow, and then after the second or third year of growth, remove the weedcloth. By the third year, most hedgerow plants can compete reasonably well with weeds.

The environment of the hedgerow is always changing, as the plants of the hedgerow grow, and interact with the diversity of crops rotating around them—this dynamic system changes by season and by year. That is one reason why each year, the diversity of insects appearing in the hedgerow and adjacent crops changes. Also, insect populations, at least some of them, can be cyclical, or, they can spike, or crash for no apparent reason.

One year might have huge populations of green lacewings feasting on holy leaf cherry blossoms in late May, the next year might have masses of lady bird beetles overwintering and spending December-February in deergrass, or large numbers of tachinid flies (parasites of stinkbugs and other insects), coming to California buckwheat blooms from June to August. Fortunately, studies (Morandin et al, 2011) have shown that nearly 80 percent of the insects in hedgerows of native perennial plants are natural enemies (beneficials). Certainly there are some pest insects, but not nearly as many compared to unmanaged, weedy field edges, where more pests than beneficials were found. So smart farmers are replacing weedy field edges with hedgerows, decreasing pest habitat, and increasing habitat for beneficials.

In addition, as the hedgerow environment evolves, new plant species may start popping up that the farmer didn’t plant, such as elder-

Continued on Page 28

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Discounted profit (US$ 1.05% discounted rate per annum) from installation of a 305-m hedgerow of native California flowering plants on a field crop edge, calculated from the cost of installation and potential cost savings incurred from hedgerows from reduction in insecticide application and pollination benefits from natural enemies and pollinators.

Scenario 4: same as Scenario 3 but with a 50% USDA EQIP cost share program.

Scenario 3: benefits from reduction in insecticide treatments each year and enhanced pollination in a pollinator-dependent crop every 3 yr.

Profit (s)

Scenario 2: same as Scenario 1 but with a 50% USDA EQIP cost share program.

Scenario 1: benefits from reduction in insecticide treatments alone each year (either no pollinatordependent crops in the rotation or managed honey bees in the system provide all pollination needs).

Years after restoration L. A. Morandin, R. F. Long, and C. Kremen. Pest Control and Pollination Cost–Benefit Analysis of Hedgerow Restoration in a Simplified Agricultural Landscape. Journal of Economic Entomology, 2016, 1–8.

Hedgerows cost money to plant and maintain, and most farmers, being businessfolk, would like to see a return on this investment. A study (Morandin et al, 2016) showed that the investment in a hedgerow, depending on what level subsidy was received, could pay the farmer back within 5 to 15 years by the reduced pesticide use and increased pollination services.

Continued from Page 27 berry, or oaks. The seeds likely come mostly from birds, oftentimes resting on the hedgerow, and excreting seeds, or squirrels forgetting where they stashed some acorns.

Hedgerows and Climate Change I’ve been talking about the dynamics of hedgerows on a relatively small scale—in the hedgerow, and on the farm. But there are much larger changes taking place, and one obvious one, to most folks, is climate change. Hedgerows can address climate change in two positive ways. First, significant amounts of carbon can be sequestered in a hedgerow (Thiel, B, et al, 2015), which can have a positive effect on a farm’s greenhouse gas mitigation potential. Farms practicing good soil management and planting hedgerows can clearly have a role in addressing climate change.

Secondly, the biodiversity which accompanies a hedgerow planting brings with it a range of species which act as natural checks and balances to pest populations, even populations of new pests, in adjacent production fields.

This provides a flexible form of pest control for the farm, and the cost is, aside from the land being used, simply the maintenance of the hedgerow.

Continued on Page 30

28

Organic Farmer

October/November 2018

Funding Sources for Hedgerows: The United State Department of Agriculture’s (USDA) Natural Resource Conservation Service (NRCS) will provide what’s known as “cost-share” funds for farmers interested in planting hedgerows. Interested farmers should contact their local USDA service center— most counties have one.

In California, the California Department of Food and Agriculture (CDFA), also provides funding for farmers to plant hedgerows as part of the Healthy Soils Incentives Program. More information about this program can be found at: https://www. cdfa.ca.gov/oefi/healthysoils/

October/November 2018

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29

Two small oaks, not planted by the farmer, growing in a hedgerow adjacent to Cleveland sage, deergrass, and toyon on the left.

California buckwheat flowers and leaf structure.

Cleveland sage in bloom. It will spread nicely to cover ground and smother weeds.

Continued from Page 28

Here are a sampling of my favorite hedgerow plants: California Buckwheat (See photos above)

Scientific name: Eriogonum fasciculatum Mature height: two to four feet Bloom time: April to September Notes: Very drought tolerant, an important food source for many native bees and beneficial insects, including syrphid flies (also known as flower flies or hover flies), predatory wasps, pirate bugs, tachinid flies, and lady beetles. Full sun to partial

30

Organic Farmer

October/November 2018

Syrphid fly feeding from California buckwheat flower. Syrphid fly larvae are voracious aphid predators.

Bumble bee gathering nectar and pollen from Cleveland sage flowers.

shade. Blooms are creamy white, last through the summer, and turn an attractive rust color when they dry down.

Cleveland Sage (See photos above)

Scientific name: Salvia clevelandii Mature height: three feet Bloom time: April to August Notes: Has attractive flowers, inviting to several bee species, butterflies, and hummingbirds. Leaves are very aromatic.

Prefers good drainage; can tolerate full sun. Watering in early stages will help it establish, but it does well in drought conditions.

Coyote Bush

(See photos, right)

Scientific name: Baccharis pilularis Mature height: 6 to 12 feet Bloom time: November to February Notes: Beneficial insectary and wildlife habitat, which hosts many insects even when not in bloom. Very good winter pollen/nectar source. Has male and female plants, and female flowers develop “fluffy” blooms once they develop seeds.

Choose between prostrate (up to 3.5 feet high) and non-prostrate (12 feet high) varieties.

Coyote Bush in Bloom.

Tachinid fly feeding at male coyote bush flower. Tachinid fly larvae are parasites of stinkbugs and other insects.

Deergrass

(See photos, right)

Scientific name: Muhlenbergia rigens Mature height: four to five feet and four to six feet wide Bloom time: May to September Notes: Clumping grass; interior is good overwintering habitat for ladybird beetles, and seed spikes are good resting places for damsel and dragon flies.

Native to most of California, Texas, and Mexico. Resilient to different soil types.

It does best with full sun exposure but will tolerate some shade and is drought tolerant. Due to its abundant yield of seed, it is a great host plant for birds, as well as beneficial insects.

These are just a few of the several dozen native perennials that might be included in a hedgerow. Remember, for the most biodiverse hedgerows, one should use plants with diverse flower and plant structures, and a diverse set of bloom times and bloom sizes. Site preparation and weed management decisions (to mulch, or not to mulch, that is one question...) are important to help avoid weeds overwhelming a new hedgerow.

More pictures and descriptions of native perennial hedgerow plants can be found at: https://attra.ncat.org/attra-pub/summaries/summary.php?pub=582 Hedgerows are not the solution to all pest problems, but they can provide some ecological stability to our agricultural systems, which by nature, are constantly being disturbed by production practices. Hedgerows are a useful, science-based, and ecologically-based tool by which farmers can creatively add

Deergrass in a farm hedgerow.

some biodiversity while reducing pest populations (and all the other benefits which accrue to hedgerows), and perhaps, even add a bit of beauty to our agricultural landscapes.

Rex Dufour is an Agricultural Specialist with the National Center for Appropriate Technology (NCAT) and is a registered Technical Service Provider (TSP) for NRCS. NCAT also implements ATTRA, the National Sustainable Agriculture Information Service through a cooperative agreement with the USDA’s Rural Business-Cooperative Service. ATTRA’s website, www.attra. ncat.org, has information about sustainable and organic production of crops and livestock, as well as more information on hedgerows and beneficial habitat (see Resources section of this article). ATTRA runs two toll-free lines which growers can call to ask any question related to organic or sustainable agriculture (800-346-9140, and Spanish toll-free, 800-411-3222).

October/November 2018

Ladybird beetles overwintering in deer grass. Groups of beetles emit an aggregation pheromone that attracts additional ladybird beetles.

Resources: A Pictorial Guide to Hedgerow Plants for Beneficial Insects. 2017. NCAT/ATTRA publication. 12 p. https://attra.ncat.org/attra-pub/summaries/summary.php?pub=582 Hedgerows and Farmscaping for California Agriculture. A Resource Guide for Farmers. 2nd Edition. CAFF. 2018.

75 p. https://www.ccof.org/blog/cafffarmers-guild-2018-hedgerows-and-farmscaping-california-agriculture Conservation Buffers in Organic Systems. 2014. NCAT/ATTRA, Oregon Tilth, Northwest Center for Alternatives to Pesticides, and Xerces Society. https://attra.ncat.org/attra-pub/summaries/summary.php?pub=464 Comments about this article?

We want to hear from you.

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Organic Soil Fertility for Cool Season Vegetables By: Richard Smith, Vegetable Crops Farm Advisor, Monterey County, CA

O

rganic production in Monterey County was worth $365 million in 2016, which was 9 percent of total agricultural value. Organic vegetables produced include baby spinach and lettuces, spring mix (arugula, mizuna and mustards), as well as full-term lettuce, broccoli, cauliflower, celery and other cool season crops. Organic vegetables are a normal part of the crop mix for all large vegetable production companies. Nutrient and pest management issues are handled by growers, pest control advisors (PCAs), seed company representatives and crop consultants, and although organic agriculture has a prominent role in Monterey County agriculture, many aspects of production are still poorly understood. A great deal of effort has been made in recent years to better understand nitrogen (N) fertility of conventionally grown vegetable crops, but much less research effort has been directed at N fertility in organic systems.

Organic N fertility is complicated by the transformation of soil organic matter, organic amendments and fertilizers from complex forms of organic N to plant available forms of nitrogen (nitrate and ammonium, a.k.a. mineral nitrogen). The decomposition of organic materials to produce nitrate is called mineralization, and is carried out by soil microbes; the speed of this process depends on adequate temperatures and moisture, and the relative quantities of carbon (C) and N (C:N ratio) in the organic material being broken down.

All photos courtesy of Kathy Coatney.

32

Organic Farmer

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Management of N Management of N in organic vegetable systems can utilize some of the concepts of conventional production such as measuring and accounting for residual soil nitrate in the soil and levels of nitrate in the irrigation water. However, organic production relies on the mineralization of soil organic matter and the addition of organic amendments and fertilizers. A key goal in organic production is building the levels of soil organic matter using cover crops and composts. However, on the Central Coast, due to the cost of land and food safety concerns, there is very little use of cover crops or compost in large-scale organic vegetable production. Most of the addition of C to these organic vegetable systems comes from the use of organic fertilizers. In an evaluation of 20 paired organic and conventional production fields the we conducted over the past two years, we observed only moderate increases in soil organic matter and soil C (Table 1, page 33) in organic production systems. We also measured N mineralization in 20 organic fields and found that on average 1.7 lbs N/A/day was mineralized from soil organic matter; the yield of the vegetables in these fields was improved by the addition of fertilizer in 17 out of 20 evaluations, indicating that mineralization of N from soil organic matter was insufficient to achieve maximum yield.

Soil Constituent

Conventional Organic

Organic Matter %

2.0

2.1

Total Nitrogen %

0.12

0.12

Total Carbon %

1.01

1.03

Phosphorous (Olsen) ppm

37

42

Phosphorous (Total) ppm

0.10

0.09

Table 1. Average of 20 pairs of conventional and organic fields1.

1 Fields were paired for the same crop and soil type.

Seasonal Crop uptake (lb/acre) Crop

N

P

K

% Nutrient removal with harvest

Broccoli

250-350

40-50

280-380

25-35

Brussels Sprouts

350-500

40-60

300-500

30-50

Cauliflower

250-300

40-45

250-300

25-35

Celery

200-300

40-60

300-500

50-65

Head or Romaine Lettuce

120-160

12-16

150-200

50-60

Baby Lettuce

60-70

5-7

80-100

65-75

Spinach

90-130

12-18

150-200

65-75

Common Organic Fertilizers

Table 2. Typical macronutrient uptake and harvest removal of cool season vegetables. Adapted from Hartz, in press.

2016

2017

4-4-2 Days Table 3. Percent of N released from 4-4-2 in surface and buried applications in 2016 and 2017; Measurement of N release from 120-0 from surface and buried applications in 2017

4-4-2

Surface Buried

12-0-0

Days

Surface

Buried Surface

0

0

0.0

0.0

Buried

0

0

0

10

30

50

7

24

30

13

31

18

31

61

15

26

46

12

59

0

25

36

65

22

25

50

12

75

31

34

64

28

33

51

15

79

38

42

66

36

35

51

14

82

44

45

68

42

33

51

17

84

52

47

69

51

34

52

26

84

60

50

66

55

36

54

32

86

63

48

70

---

---

---

---

---

Both spinach and lettuce have a high demand for N over a short period of time during the crop cycle. For instance, during the first two weeks of the crop cycle of spinach, during crop establishment, it takes up only 7-10 lbs of N/A. However, during the next 14 to 20 days until harvest, spinach takes up as much as 5 lbs N/A/day. During the first 30 days of the lettuce crop cycle, total N uptake is 15 lbs N/A, but during the next 5 weeks N uptake is 3.6 lbs N/A/ day. Based on this N demand, it is clear why maximum yield cannot normally be achieved with the mineralization of N from soil organic matter alone.

Calculating How Much to Apply Calculating how much organic N to apply to fast growing leafy vegetables is tricky. Total crop N uptake provides a sense of how much N to apply to a crop (Table 2, above). In conventional production measuring residual soil nitrate prior to the first fertilizer application helps fine tune how much fertilizer N is needed. That is also partially true in organic production. However, there are two issues for fast growing leafy vegetables, 1) short crop cycle and 2) the time it takes for nitrate-N to be released from organic fertilizers. For these crops, the

only time that you can react to measurements of residual soil nitrate is prior to planting or very early in the crop cycle because later in the crop cycle there is not enough time for the organic fertilizer to release nitrate-N (Table 3, left).

However, the predictive value of preplant soil nitrate measurements can be diminished to some degree if significant leaching occurs with the water used to germinate the crop. Measuring residual soil nitrate after the germination phase of the crop could improve the estimates of available residual soil nitrate. However, the fast crop cycle of the baby vegetables and slow rate of release of organic fertilizers, necessitates making fertilizer decisions early in the crop cycle and measurements of residual soil nitrate are the best measure that we have for adjusting fertilizer applications.

October/November 2018

Commonly used organic fertilizers on the Central Coast include chicken manure and various by products from slaughter houses such as feather, meat, bone and blood meals. These materials have characteristic N release curves. In 2016 and 2017, evaluations of 4-4-2 (a mix of chicken manure, and meat and bone meals) were conducted by placing 20 grams of fertilizer in polypropylene pouches; the pouches were applied to the soil in two ways to simulate field applications: 1) buried 3 inches deep to simulate incorporated applications and 2) by placing the pouches on the soil surface to simulate surface applications (a.k.a. drop-on-top). Pouches were placed in commercial lettuce production fields at the beginning of a lettuce crop cycle. Four pouches were collected each week and the contents were dried, weighed and analyzed for N, phosphorus (P) and potassium (K); the rate of disappearance of nutrients from the pouches estimated the amount made available to the crop. The average percent of N released from 4-4-2 over the two years was 62.1 percent for material buried in the soil and 42.2 percent for surface application (Table 3, left). It is interesting to note that the rate of release of N in 2016 was more rapid than 2017 which emphasizes the importance of soil temperatures on the Continued on Page 34

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33

Material

2 weeks 4 weeks 8 weeks

2.5-2.0-2.5 4

6

14

4-4-2

29

31

38

8-5-1

47

44

59

10-5-2

44

49

59

12-0-0

49

57

59

These evaluations show that not all the N applied in a fertilizer application will become available for the crop.

The portion of the

organic fertilizer that does not mineralize during the crop cycle has two fates: 1) contributes to residual soil nitrate in the soil and 2) becomes part of soil organic matter. Growers applied from 1.2 to 4.8 times more N than the crop took up in 20 evaluations over the past two years. However, discounting the amount of N that mineralized from the organic fertilizer, organic fertilizer applications in this survey ranged from 0.4 to 2.7 times crop N uptake.

Table 4. Estimates of percent of N release from various organic fertilizers in laboratory incubations conducted at 68 °F.

Continued from Page 33 release of nitrate from organic fertilizers. The difference between surface vs buried applications was more exaggerated for 12-0-0 with 31.5 and 86.0 percent of the N released, respectively (Table 3, page 33).

The release of N from organic fertilizers follows a typical pattern with initial rapid release of N followed by a slow, steady release that extends over a long period of time. Incorporating the fertilizers into the soil increases the initial rate of N release; fertilizer with a higher N concentration showed faster N release.

It is possible that the pouch evaluations overestimate the N release rate because of movement of small particles of fertilizer that filtered out of the pouch; this idea is supported by observations in a laboratory evaluation conducted at Davis that showed about a 20-30 percent lower rate of N release of 4-4-2 and 120-0 over the same period of time (Table 4, above).

Soil P values at each survey site were relatively modest for the Salinas Valley vegetable ground, except for one that was located on an old dairy. Bicarbonate extractable P values ranged from 10 to 57 parts per million (ppm) with a mean of 37 ppm on the non-dairy sites (Table 1, page 33). The moderate P values occurred in spite of the common usage of 4-4-2 which has a ratio of 1:1 of N:P2O5. Interestingly, we did not observe higher levels of total P in the organic farms. The form of P in 4-4-2 fertilizer comes mostly from bone meal, which is not soluble at soil pH greater than 7.0; all survey sites had pH above 7.0, meaning that bone meal is a highly inefficient P source in this production system. In fertilizer pouch Evaluation 1, 17 percent of phosphorus was released after 63 days in both surface and buried applications. Based on this survey, it appears that soil bicarbonate extractable P levels do not rise rapidly due to the use of 4-4-2. By contrast 82 to 92 percent of the K contained in 4-4-2 was rapidly released to the soil.

Take-home message The release of N from soil organic matter only contributed a small portion of the N required for high-N demanding leafy green vegetables. Residual soil nitrate makes a significant contribution to the N needs of the crops. However, measurement of residual soil nitrate N

34

Organic Farmer

October/November 2018

must be taken far enough ahead in the crop cycle to be able to adjust the quantity of fertilizer applied. For instance, in 2018 we had a trial in a spinach field that had 25 ppm nitrate-N on a clay loam soil prior to planting, we cut the preplant application from 2000 lbs to 1000 lbs 4-4-2 and with no reduction in yield. In the Central Coast production fields, 2nd or 3rd crops of the season can often have high quantities of residual soil nitrate which allow growers to reduce fertilizer applications.

The quantity of nitrate-N in the irrigation water can also make significant contributions to the N needs of crops.

The quantity of N in irrigation water can be calculated by this formula: ppm Nitrate-N x 0.23 = lbs N per acre inch of applied water The quantity of N supplied by the water with 20 ppm nitrate-N is rather modest but becomes increasingly significant as levels increase up to 40 ppm nitrate-N; nitrate-N in irrigation water contributes a significant percentage of the crop needs at quantities beyond 40 ppm.

The fate of N not released from organic fertilizer after the crop cycle is not well understood, but presumably it becomes available to future crops, mineralizing at a slow, steady rate similar to soil organic matter. The high usage of 4-4-2 which is a mix of chicken manure blended with meat and bone meal on larger-scale organic farms brings the benefits of adding significant amounts of organic matter to ranches that may not have extensive cover crop or compost programs. For instance, 2-3,000 lbs 4-4-2 per crop 2-3 times per season adds 2-4.5 tons of carbon-rich organic matter to the soil.

Many of the concepts described here are for fast-growing leafy green vegetables.

They may not apply to longer-season crops that have more time to root deeper, scavenge N from deeper in the soil profile and take up the N that they need.

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