Soil Fertility Strategies on Organic Vegetable Farms

Final Report for LNC05-258

Project Type: Research and Education
Funds awarded in 2005: $72,056.00
Projected End Date: 12/31/2009
Region: North Central
State: Wisconsin
Project Coordinator:
John Hendrickson
CIAS, UW-Madison
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Project Information


Soil fertility is a top research priority as ranked by organic growers in general—and organic vegetable growers in particular. This project documented the soil fertility practices employed by organic vegetable growers in Wisconsin and Illinois, gathered grower information needs and research questions, generated a set of cases studies highlighting contrasting fertility management strategies, and has helped provide baseline data for ongoing organic research and outreach programming at the University of Wisconsin and University of Illinois. Growers participated in all phases of the project, including development, implementation, and evaluation.

Methods included a survey, case studies, and facilitating interaction and communication between growers and university researchers. Publications, field days, and workshops have been used to communicate results and solicit feedback. Outcomes include an increased knowledge base among growers and university specialists, changes in grower practices based on an increased understanding of soil fertility management options and their cost and impacts, and expanded organic research programming at universities.

In addition, this project identified a need to conduct further education and outreach on the following specific issues:

1. Helping growers understand the value and utility of regular soil tests to monitor nutrient levels, pH, organic matter, and aggregate stability scores. Many growers reported not understanding soil test results or struggling to put recommendations into practice. Others mistrusted the information because it is not geared specifically to their organic farming practices and principles.

2. Working with soil testing laboratories to better communicate soil test results and recommendations to serve the needs of organic growers.

3. Managing soil phosphorous inputs to reduce the excessive P loads common on many Wisconsin farms with a livestock (dairy) history. Some farms may be contributing to excessive phosphorous levels through their use of poultry based fertilizers and manure based composts.


Organic growers in general—and organic vegetable growers in particular—have consistently ranked soil fertility as a top research priority. This project documented the soil fertility practices employed by organic vegetable growers in Wisconsin and Illinois, gathered specific grower information needs and research questions, generated a set of cases studies highlighting contrasting fertility management strategies, and has helped influence the development and advancement of organic research plots and research programming at the University of Wisconsin and University of Illinois. Methods included a survey, case studies, and field days. Publications, field days, and web videos were and are being used to communicate results and solicit feedback.

Outcomes have included increasing the knowledge base of growers and University specialists, changes in grower practices based on an increased understanding of soil fertility management options and their cost and impacts, and advancing organic research programming at universities and their respective research farms.

The vegetable industry in the North Central Region features both significant processing vegetable acreage and a large and growing fresh market industry dominated by many small farms. This project focused on the latter group but results are relevant for many different types of farms. In Wisconsin, in 2007, there were 2,145 farms that produced vegetables, potatoes and melons (USDA, 2007). Illinois’s fresh market industry was about half that size, with 1,047 farms. In terms of acreage, Wisconsin had roughly three times as many acres in vegetables, potatoes and melons in 2007 with 55,764 acres compared to Illinois with 17,670. Organic farms and acreage comprise a much more significant sector in Wisconsin than Illinois. Based on 2008 data, Wisconsin had 254 farms producing certified organic vegetables and Illinois had 68 and the acreage figures were 1,749 and 230 respectively.

Organic vegetable growers face a common challenge regardless of specific crops grown, farm scale, or marketing strategy. Vegetable growers export significant amounts of biomass and nutrients off their farms each year. To maintain or improve crop yields and quality—and uphold the soil building tenets of organic farming—organic growers endeavor to improve soil health and supply nutrients through a wide variety of strategies. These include short-term cover cropping, spreading compost or manure, rotating cash crops with long-term (sod) cover crops, and applying various approved fertility amendments.

Prior to the project, direct personal communication between the project coordinators and growers indicated that growers questioned how well their cover cropping schemes provide fertility for subsequent crops and whether they were making sufficient progress toward improved soil health (such as increases in both biologically active and stable organic matter pools). Many growers also aspired to implement longer-term rotations but lacked sufficient land or proof that such rotations were economical.

There has been some speculation about nutrient imbalances on organic farms but a lack of soil test data to confirm or refute the build up of available nutrients on organic farms, particularly those that might impair water quality (N and P). It is possible that few organic farmers test their soil because soil testing and interpretation of test results are geared toward conventional farmers. There is a clear need to document the use of soil testing in soil fertility management and to help organic growers interpret and take advantage of soil test results.

Another question relates to the use of un-composted manure. Critics of organic farming often site the health risks associated with using animal manure but there is no specific documentation indicating how prevalent the use of un-composted manure really is and, if it is used, how and when.

Another question posed by the research team was to learn whether the USDA National Organic Program (NOP) has influenced compost use. Although NOP created a compost task force to develop new guidelines for producers and certifiers that make composting easier to achieve on organic farms (,
some growers may no longer compost on farm or import compost from off farm.

The rationale behind this project was that an important first step in documenting and understanding the impacts and benefits of various fertility strategies is a close examination of the current practices used by growers while simultaneously gathering information from growers about research needs and priorities.

Literature Review

The general benefits of cover crops and compost are well-documented (SAN; Hendrickson[1]; Magdoff and van Es) and most organic vegetable growers are committed to their use and show great skill and ingenuity in incorporating these soil enhancing practices into their farming systems. Numerous SARE and Organic Farming Research Foundation projects have investigated related issues, such as optimizing specific cover cropping schemes for fertility, weed suppression, or reduced tillage often for a specific vegetable crop (e.g. Weller; Gallandt; Scholberg). However, there have been no comprehensive and detailed studies that document current fertility practices in use or comparisons of fertility strategies across farms.

A study by Fernandez-Cornejo, et al. reports that organic vegetable growers rely primarily on traditional organic processes such as green manuring, animal manuring, composting, and crop rotation to supply crop nutrients. According to their survey, animal meal, fish products, and lime are the most frequently reported supplemental nutrient sources with 14, 20 and 28% of organic growers, respectively, reporting that they use these materials. Details about these fertility management practices were not gathered, however, nor was there any assessment of their costs and benefits.

Organic growers in general—and organic vegetable growers in particular—historically rank soil fertility as a top research priority (Walz). An Organic Farming Research Foundation national survey found that fertility management issues are a high research priority for organic growers. Three different fertility management topics were ranked 2nd, 5th, and 6th out of a list of thirty-two other research topics by all organic growers while these same fertility topics were ranked 1st, 2nd, and 6th by vegetable growers (Walz).

No one knows how prevalent various soil fertility practices are within the organic vegetable grower community. Literature and communication with growers suggests that many growers rely on off-farm sources of manure, especially poultry litter. Some have questioned the sustainability of this practice and new phosphorous management standards may prevent growers from applying enough manure to supply crop nitrogen needs. A study titled "Contradictions in Organic soil management practices: evidence from 31 farms in Maine" which was presented at the 2nd International IFOAM (International Federation of Organic Agriculture Movements) Conference in Montreal, CA in October 1978, found that the great majority of organic farms in Maine utilized a very simplified fertility regime that relied minimally on on-farm fertility management such as legume rotations and cover crops and instead relied primarily on cheap off-farm chicken manure. The authors express concern that with the Maine poultry industry in decline, most of the organic farmers in Maine were in a very economically vulnerable partnership. The authors were also concerned about the ecological consequences of most of Maine's organic farmers depending on heavy annual applications of poorly composted poultry manure.

Organic agriculture has come along way since 1978 but it may still be true that many organic vegetable farmers are still dependent on off-farm sources of manure. A 1993 survey of organic vegetable growers in Florida revealed that over 70% of growers relied on chicken manure or bagged organic fertilizer (also based primarily on poultry manure) for plant nutrients. The latest Organic Farming Research Foundation survey ranks fertility practices by frequency (cover crops ranked first followed by compost applications) but there is no detail and no breakdown of the data by type of farm or crop (Walz). Similarly, a study by the USDA Economic Research Service in 1994 concluded that 77% of vegetable growers use legume cover crops, 78% apply manure, and 61% apply compost but there is no further breakdown or definition of these practices (such as the source and quality of the manure or compost).

Personal communication with growers in Wisconsin prior to this project suggested that poultry litter is a common source of nutrients (Hendrickson) combined with various annual cover crops. Furthermore, on-farm integration of crops and livestock and complex rotations that include both row (cash-) crops and sod crops was perceived by the research team to be uncommon on the vast majority of organic vegetable farms in Wisconsin and Illinois.

In regards to the criticism that organic farms pose a threat to human health due to the potential presence of pathogens in manures applied as fertilizer, there seems to be no precise data about the prevalence or timing of manure applications on organic vegetable farms. The Organic Farming Research Foundation survey found that the use of raw manure was only used “frequently or regularly” on 22% of all farms (OFRF, 1) but it would be useful and important to know more, especially in regard to fresh market vegetable farms that sell raw products directly to consumers. Of course, the USDA organic rule contains specific guidelines for how and when manure can be used and organic farms are inspected to make sure such practices are followed (a safeguard not in place for both “uncertified organic” farms or non-organic farms).

The Organic Farming Research Foundation’s State of the States report criticizes many Land Grant Colleges for the lack of research and infrastructure to support organic farming through scientific inquiry (Sooby). This project hoped to address this critique by providing a framework to establish organic plots at University of Wisconsin research farms and expanding work underway at the University of Illinois to document soil fertility changes under various organic transition approaches (Eastman).

Project Objectives:

This project sought to document the soil fertility practices employed by organic vegetable growers in Wisconsin and Illinois, gather grower information needs and research questions, generate a set of cases studies highlighting contrasting fertility management strategies, and provide input into organic research programming on University of Wisconsin and University of Illinois research farms. Short-term outcome goals included:

• Increase the knowledge base of growers and University specialists on the range of soil fertility strategies employed by organic vegetable growers and
• Increase awareness among organic growers of soil fertility options available to them and the cost and benefits of different practices and strategies.

Intermediate-term outcome goals included:

• Changes in grower practices based on an increased understanding of soil fertility management options and their impacts and
• Increasing organic acreage on University research farms

Long-term outcome goals included:

• Enhancing the sustainability of organic farming and
• Engendering future organic research and programming at Land Grant Universities.

Progress and analysis on these outcomes is reported in the Results and Discussion section below.

In terms of the completion of objectives and performance targets, the following is a year-by-year summary.

We began the process of conducting a grower survey to quantify the types and prevalence of different soil fertility practices. A database of growers was created by using lists from organic certifiers, grower groups and networks, and existing databases managed by project collaborators.

Following our project methods, we also initiated a pre-test of the survey among a group of University colleagues as well as organic farmers serving as advisors to the project.

2005 was also when we original planned to select a group of case study farms for a more in-depth look at specific soil fertility management approaches and practices. We changed our plans, however, because we decided it would be better to utilize the survey data to identify common and intriguing management practices as well as broaden the potential pool of case study candidates beyond the farms with which the project coordinators were already familiar.

Activities in 2006 included the completion and analysis of the mailed survey, and select the case study farms.

Drafting the survey with input from several collaborators and then pre-testing it with our grower advisory group was completed in early 2006. Surveys were then sent to a database originally containing 385 growers. We learned later that this list contained a large number of organic farms that do not produce vegetables and this prompted a database cleaning process in order to determine our actual population size and response rate. After cleaning, the database shrank to 181 growers.

In this year of the project, the main goal was to complete the analysis of the mailed survey, communicate results, select the case study farms, and begin collecting data on those case study farms. In addition, we planned to produce various outreach materials (presentations, poster) and begin sharing results with interested stakeholders. These activities were accomplished with the change that we decided to select 12 case study farms rather than 8. This decision was based on the desire to include a wider representation of dominant management practices and facilitate better opportunities for comparisons across farms. This was possible financially because we shortened the length of the case studies to two years from the original three years.

In 2008 we continued to work with the 12 case study farms to collect data, held two on-farm field days, and prepared a report on the results of the grower survey (completed in 2006/2007). In addition, we pursued opportunities to integrate the information we learned and the direct perspectives of growers into the ongoing programming at both the University of Wisconsin and the University of Illinois.

A second year of data collection on the case study farms was completed and another set of field days were held in Wisconsin and Illinois. Year 2 soil samples were collected and analyzed by the University of Wisconsin and University of Illinois laboratories. A webinar was held with case study participants reviewing some of the soil test data as well as looking at opportunities for future investigations and activities.


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  • John Henrickson


Materials and methods:

Methods included (1) a grower survey, (2) producing a set of quantitative and qualitative case studies, and (3) working with an advisory board of organic growers to lend expertise and input into this project as well as broader university research programming.

Advisory Board
An advisory board of organic growers was established to assist with the following tasks and activities:

1. lend expertise in the on-farm realities of fertility management,
2. assist in the development of the survey
3. help select the case study farms
4. ensure the project is relevant and useful for growers
5. provide direct input to the development of organically managed University research plots , and
6. evaluate both project results and the project itself.

Grower survey
The grower survey sought to quantify the types and prevalence of different soil fertility practices and how they may have changed over time in regards to compost as a result of USDA-NOP regulations. We developed a survey instrument of questions that addressed all aspects of soil fertility management from inputs like fertilizers, manure and compost, on farm composting, rotation, tillage and use of cover crops. The survey had four basic sections:

1. General information about each farm and farming operations—such as farm size, soil type, farming history, types of crops and/or livestock grown/raised, etc.
2. Soil fertility practices and strategies—including types of rotations used, cover crop types and types of soil amendments used (fertilizers, manure, composts, teas, microbial inoculants or other biological preparations, biodynamic amendments, etc.)
3. Attitudes and perceptions—what is their perception of interactions between soil fertility and weed, pest, and disease pressure on their farms? How important is soil fertility in the overall management of their farm? Do they feel that they have a good working knowledge of how to manage soil fertility optimally on their farm?
4. Questions and research needs—what kinds of resources and research do they need to increase their knowledge and soil fertility management practices?

Within the context of these general survey sections, several issues were probed in particular, including:

Issue 1—Composting and compost use: If compost is used, in what parts of the farming operation is it used—field application, greenhouse growing medium, other? How do growers use compost in each aspect of their farming operation, including: type, timing, frequency, and application rates. Do they make it themselves or do they purchase compost? If they make compost, what kind of feedstocks do they use and how do they manage compost piles? Have the NOP Standards for composting affected the way they produce compost? If they purchase compost, where do get it from, what characteristics are they looking for in the compost and do they request information from the compost producer to demonstrate that the compost meets the NOP rule requirements?

Issue 2—Soil testing: Do they soil test? If no, why not? If yes, from how large an area are samples collected? How frequently to do they analyze their soils? What kind of analyses do they have run? Where are samples tested? Does the testing lab provide interpretation of test results that are useful? Do they use test results with or without interpretation to make soil fertility management decisions? If so, how? If they don’t use soil test results to make fertility management decisions, what would they consider is needed to make soil testing and test results more meaningful?

Issue 3—Manure, other organic fertilizers and soil amendments. Is manure used as a fertility source? If so, how do they decide application rates and timing of application? What types of manure do they use? Is manure generated on the farm or purchased from off-farm sources? If purchased from off-farm, how much do they pay (per ton or cubic yard) and how far away does it come from? What kinds of organic fertilizers or soil amendments do they use? How do they decide methods, timing, and rates of application? How do they evaluate the efficacy of soil amendment products?

Issue 4—Rotations. How would they describe the management philosophy they use to design their rotation? What is the rotation duration? What kind of crops and cover crops are included? Do they use permanent perennial vegetation for part of the rotation? Is livestock grazing part of the rotation? What strategies do they use to transition land into organic production?

Issue 5—Tillage. How frequently are soils tilled and what kind of tillage equipment and methods are used? What is their perception about interactions between soil tillage and soil fertility?

Both certified organic growers and growers who follow organic practices but are not certified were included in the survey sample. “Non-certified organic” growers represent a large and important group due to the prevalence of direct marketing in the upper Midwest including farmers’ market and community supported agriculture (CSA). Many of these growers rely on direct interaction with customers rather than on third party certification to satisfy consumer concerns about food safety and farming practices.

Proven, standard mailed survey methods based on Dillman were used to ensure an adequate response rate (Dillman). Working with the advisory board, the survey instrument was tested by growers before being administered. Follow-up phone calls or email was used to ensure data accuracy in cases where answers were incomplete of confusing. Growers who mailed in completed surveys were rewarded with a gift. Respondents had a choice of the following books:
Managing Insect on Your Farm: A guide to ecological strategies, Building Soil for Better Crops, Managing Cover Crops profitably or Building a Sustainable Business.

Surveys were then sent to a database originally containing 385 growers. We learned later that this list contained a large number of organic farms that do not produce vegetables and this prompted a database cleaning process in order to determine our actual population size and response rate. After cleaning, the database shrunk to 181 growers.

Reminder post cards and a second mailing of surveys were sent to bolster our response rate. Just over 100 surveys were returned. Weeding out non-organic or non-vegetable farms reduced the number of usable surveys to 88. Our response rate was, therefore, 49%.

Analyzing the survey data began in the spring of 2007 and continued until January 2008. Results and discussion of survey findings appears below in the Results and Discussion section.

Case studies
The case studies were meant to afford an opportunity to highlight both typical and exemplary fertility management approaches as well as to describe the costs and benefits of contrasting fertility management systems. Farms were selected on which to monitor soil nutrient levels, percent organic matter, pH, aggregate stability, and other characteristics over a two-year period. The specific test and procedures were as follows:

We collected soils samples once per year in the fall in the same fields on each farm. We asked growers to take one composite soil sample per field in the top 6 inches (soil surface). They sent one portion of the sample to the University of Wisconsin Soil and Plant Analysis Lab for a routine soil test (organic matter, pH, P, K). They sent another portion of the sample to Dr. Michelle Wander’s lab at the University of Illinois, Department of Natural Resources and Environmental Sciences to measure nitrogen, particulate organic matter—POM, a measure of biologically active carbon—and aggregate stability.

The case study farms featured different combinations of fertility practices so that contrasting approaches could be monitored and evaluated. Our original approach was to make sure to include farms with the following characteristics:

1. annual green manure cover cropping only;
2. annual cover crops plus fertility amendments (e.g. soybean meal, fish emulsion, etc.);
3. annual cover crops plus manure and/or compost (ideally we would include farms with significant on-farm sources of manure and or compost as well as examples of farms who import those materials from off-farm sources.
4. annual cover crops plus a one or more year fallow rotation involving a legume/grass sod.

Final selection of case study farms depended on survey results. The above categories were useful selection criteria but, as the project progressed, other factors also became important as is discussed below in the Results and Discussion section.

The case studies also included financial information on the costs and labor requirements of different fertility practices, discussed below in the Results and Discussion section.

Research results and discussion:

Results and discussion is broken down by activity (method), including the survey, case studies, and the advisory board.

Survey Results

After receiving training and approval through the UW-Madison Human Research Protections Program and Institutional Review Board (IRB), the survey was mailed in winter 2005/2006 to 181 organic (certified and un-certified) vegetable growers in Wisconsin and Illinois. The mailing list was a combination of databases from the University of Wisconsin-Madison’s Program on Agricultural Technology Studies (PAST), the Illinois Farm Direct ( mailing list, the University of Illinois Agroecology and Sustainable Agriculture program, the Madison Area Community Supported Agriculture Coalition (MACSCAC), the Home Grown Wisconsin marketing cooperative, the Midwest Organic Services Association (MOSA) and the Organic Crop Improvement Association (OCIA). All of these lists were combined and any duplicates and non-vegetable growers were removed.

Given the modest size of the database, we elected to mail surveys to all addresses rather than take a random sample. Surveys were administered during the winter of 2005/2006. After mailing the first round of surveys, a set of reminder postcards was mailed two weeks later. Then a second mailing of surveys was sent out to non-responders followed by a final round of reminder postcards. We received 96 completed surveys. Some of these were eventually discarded because they came from farms that were not organic or did not grow vegetables. We ended up with 88 usable surveys for a response rate of 49%. We believe this high response rate is an indication of the dedication and commitment of organic vegetable growers, good relationships between University personnel and the grower community, and the importance of fertility management as a key challenge facing growers.

Statistical analysis of the survey data began with simple frequencies, averages, medians, and ranges. Following that, a 2-way frequency table with a chi-square test was used. If several variables were thought to influence certain answers, a logistic regression was performed. We used SAS analyses to look at relationships between demographic and response variables. In this analysis, a logistic regression was performed to tease out salient or statistically significant relationships.

To conduct the logistic regression, we needed to create simplified categories for the many questions with multiple response variables. For questions where three or more answers were possible, responses were grouped into more broad categories. For example, the question on organic fertilizers and soil amendments was originally written as a list of specific fertilizers or amendments, then later collapsed into these three categories: 1) Nitrogen rich - soybean meal, kelp meal, blood meal, bone, feather, and fish, 2) Other nutrient source - wood ash, lime, colloidal phosphate, rock phosphate, potassium sulfate, potassium magnesium sulfate, granite dust, and greensand, and 3) Biological - rhizobia, and mycorrizae.

If logistic regression analysis produced at most one statistically significant regressor variable, a 2-way frequency table with a chi-square test was performed. For example, we asked the question “are farmers with an established rotation plan more likely than those farmers without a plan to do soil testing, nutrient budgeting and other more quantitative practices, such as measuring fertilizer, manure or compost application rates or evaluating efficacy of soil amendments.” We were also interested in relating demographic variables that characterized farmer experience with variables characterizing their soil fertility management practices. We used a probability value of 0.05 or less to determine statistical significance.

Farm and Farmer Characteristics
The majority of growers who filled out the survey were highly educated and had more than 10 years of farming experience. In regards to education, 87% of the respondents had had some level of college and/or a college, professional, or graduate degree. The bulk of the respondents were male (70%). The average age of the survey respondents was 46 years old, which is significantly less than the national average age of farm operators. The National Agricultural Statistical Services (NASS) 2007 Census of Agriculture reports that the average age of U.S. farm operators increased from 55.3 in 2002 to 57.1 in 2007. Moreover, the number of operators 75 years and older grew by 20 percent from 2002, while the number of operators under 25 years of age decreased 30 percent (2007 Census of Agriculture). In contrast, the majority of the respondents (68%) in our survey were either between 26-49 (33%) or 50-56 years old (35%). Table 1 (see attached file) summarizes the demographics of the survey respondents.

TABLE 1: Respondent Demographics and Characteristics
[See attached file]

The basic descriptive statistics for farm characteristics show a blend of small, middle and large farms with a similar percentage of farms sized between less than 1 and 6 acres (53%) and farms from 7 to more than 25 acres (47%). See Table 2 in the attached file for a summary of farm scale, income, and soil types. The majority of farms (55%) were generating up to $20,000 from the sale of veggies, melons, herbs and flowers. The majority of farms (60%) are extremely diverse, producing vegetables, livestock, and other additional crops (see Figure 1 in attached file).

TABLE 2: Farm Characteristics
[See attached file]

FIGURE 1: Farm Diversity
[See attached file]

Table 3 helps characterize the respondents in terms of farming practices and operations. Most farms utilize a row crop system (76%) while a significant percentage use a temporary raised beds (37%). Many farms use both. The use of mulch, both natural (straw, hay) and plastic was very commonplace. Almost half the farms reported the practice of multi-cropping—the practice of using a piece of ground for more than one crop in a given year. Obviously, soil fertility management becomes more challenging and important with this type of intensive land and resource use. No-till—a practice currently gaining attention from both growers and researchers—was only reported by 3% of the respondents.

TABLE 3: Practices used in Vegetable Operations
[See attached file]

One question the survey sought to answer was how intensively growers use their land. Our assumption going into the project was that many growers do not have a very large land base and thus cannot rest significant amounts of their land in fallow cover crops. In order to answer this question, we determined the ratio between the total amount of acres used in a grower’s operation and the amount of that land in actually vegetables in a given year.

Nearly 55% of the growers used less than one quarter to three quarters of their available land for vegetables in 2005. Forty percent used half or less of their land for vegetables. About 46% had more than three quarters of their available land in vegetables. We had anticipated more farms to be in position of using three quarters to one hundred percent of the land each year.

TABLE 4: Percent of land used for vegetables each year
[See attached file]

Related to land use intensity is the use of perennial vegetation in the cropping system rotation. Our survey results showed that over half the farms included perennial vegetation for one year or longer into their rotation. Illinois farms were more likely to have perennial vegetation as part of their rotation than Wisconsin farms (Table 6). In contrast to what we hypothesized (growers who had been farming longer might have adopted longer, more diverse rotations, including the use of longer-term perennial cover crops), farmers were less likely to incorporate perennial vegetation in their rotation the longer they resided on their current farm (Table 6). One possible explanation is that longer-term farmers use more of their land to meet increasing production demands, rather than leaving it in perennial cover crops that are less likely to generate income.

Fertility Management
The grower survey explored a wide range of fertility management issues including 1) composting and compost use, 2) other inputs (including manure, organic fertilizers and soil amendments, 3) intensity of land use and rotations, and 4) tillage. This section summarizes some of the results utilizing key questions we had entering the project.

1) Do most vegetable growers farm intensively on smaller acreages without much land to rotate crops?

While 36% of our respondents farm less than 3 acres and 53% farm less than 6 acres of vegetables, there 47% are above 7 acres with 19% farming over 25 acres. Although nearly 46% of farms used 75 to 100% of their land for vegetables, a robust 55% used less than 75% and an impressive 40% used less than half their land (see Table 4).

Those at a smaller scale tended to have less land available for cover cropping and crop rotations, however. Sixty eight (68) percent of farms less than 3 acres and fifty three (53) percent of farms between 3 and 6 acres used 75% to 100% of their land for vegetables in a given year. In contrast, larger farms frequently had ample land for rotation and cover cropping. Thirty seven percent of farms above 7 acres used less than 50% of their land for vegetables in a given year.

Additionally over half the farms incorporated permanent perennial vegetation that stays in place for more than a year into their rotation. Smaller farms were just as likely to maintain land in perennial cover as part of their rotation as larger farms. The length of growers’ rotation plan was also not significantly affected by farm size. However, the longer the time on the current farm, the less likely growers were to incorporate permanent perennial vegetation in their rotation.

The duration of the respondents’ crop rotation was related to marketing strategy and gross income level. Farms selling mostly to wholesale or processors were more likely to have shorter rotations. Farms with a smaller percent of gross income from vegetables sales were also more likely to have shorter rotations.

Illinois farms were more likely to have perennial vegetation as part of their rotation than Wisconsin farms

2) Is raw manure use as prevalent as some detractors of organic farming assume?

Use of uncomposted manure was reported by almost 50 percent of farms. In contrast, nearly 70 percent reported using compost. The most frequent time for manure application is in the fall, a practice that helps farms comply with the strict rules about manure use on organic farms. Sixty one percent of farms keep livestock themselves and 29% utilize livestock grazing as part of their larger crop rotation meaning that the manure is applied directly to fields in perennial cover by the animals themselves.

TABLE 5: Uncomposted Manure Use
[See attached file]

3) How extensive is compost use and how have the USDA Organic standards influenced its production and use?

Compost use was reported on 69% of the farms (see Table 6). Many farms (70% of compost users in our survey) use compost as an ingredient in a greenhouse potting soil mix. However, an even greater number of farms (77%) apply compost to their fields. The most common rate of application was 1 to 5 tons per acre (65%) and the most common frequency was every year (48%). The number of years farming was the only variable that influenced how farmers determined compost application rates. The more years farming made it more likely that personal experience and compost test results determined application rates. Farmers were more likely to rely on “wild guess” and/or compost test results with fewer years experience.

An impressive 82% make some compost on their farm although 47% buy compost from commercial sources. Farms were more likely to use compost and less likely to use manure as the percent of farm income from the sale of vegetables increased.

Most farms (73%) indicated that the USDA standards for certified organic compost have not affected their production. Anecdotal evidence suggests that farms still making compost often treat it as they would manure because they are not following the USDA standards. Only 7 farms (12%) indicated that they used to make compost but no longer do so. The challenges associated with following the USDA NOP standards for compost was the most frequently cited as a reason for no longer making compost.

TABLE 6: Compost Use
[See attached file]

4) Do growers test their soil regularly and how do the utilize test results?

The majority (82%) of our survey respondents stated they had performed a soil test on their farm (see Table 3). A slightly larger percentage (83%) use soil tests to inform their soil fertility management strategies. Out of those respondents who have performed soil tests, the largest group, 44%, tests their soil every 3-5 years (see Table 7). Curiously, the smaller the farm size (owned + rented), the more likely the farmer was to have soil tests conducted. Farm that were certified organic were more likely to soil test than those that were not certified.

TABLE 7: Soil Testing Practices

Attitudes and Perceptions
Some survey questions were designed to gather opinions, attitudes and perceptions, including research and education needs.

Seventy percent (70%) agree or somewhat agreed with the statement "I believe I rely too heavily on tillage for seed bed preparation, weed management, and/or cover crop incorporation and would like to find ways to reduce the frequency and/or intensity of tillage I use."

With regard to growers’ perceptions of their farm’s nutrient budgets, 47% perceived that micronutrients were in inadequate supply on their farm (compared to 26% for nitrogen (N) and 17% for phosphorous (P) and potassium (K)). Nearly a quarter felt that P and/or K were in excess supply in their soil (compared to only 5% for N and 18% for micronutrients). The fact that only 24% perceived that P is in excess supply, suggests that there might be a need to measure P levels on organic vegetable farms to determine if their perceptions match reality. The amounts of P available to plants in Wisconsin agricultural lands have nearly doubled over a forty-year period (1964 to 2004), due mainly to excess manure and phosphorus fertilizer application (Peters 2005). There is concern that excess soil P concentrations lead to excess P in rivers and lakes, leading to degradation of water quality. It would be important to determine if organic vegetable farms contribute excess soil P to surface waters, particularly relative to other types of farming operations such as livestock production.

Cover cropping sequences and rotations, and strategies for building and maintaining organic matter were the two issues that respondents rated as the most important research topics for universities. There was also a strong interest in research focused on the interactions between soil fertility practices and weed, insect and disease pressures. Other soil fertility management issues that were highlighted as being important included: 1) the influence of different practices on amount and timing of nitrogen availability, 2) on-farm composting and use, 3) managing carbon: nitrogen ratios in crop residue and influence on nutrient availability, and 4) the influence of practices on phosphorous and potassium levels/run-off/leaching.

Fertility Management Matrix

In order to get a better sense of how growers are managing fertility, we created four management categories based on the intensity of land use and relative intensity of fertility inputs. The criteria for these management category designations included:
• Ratio of total vegetable acres/total acres in veggies and related crops
• Length (duration) of crop rotation
• Use of permanent perennial vegetation in the rotation
• Livestock grazing as part of rotation
• Commercial Fertility Inputs—types and frequency
• Compost—use, frequency, and application rates
• Manure—type, use, and application rates

We then created the following four management categories:

1. Land Intensive, Minimal inputs. This group is characterized by farms that use 75-100% of their land base for vegetables in a given year and use minimal fertility inputs beyond cover cropping.

2. Land Intensive, High inputs. Characterized by farms that use most of their land for vegetable production each year and use significant amounts of nutrient rich inputs such as manure, compost, and high nitrogen fertility products (such as liquid fish, alfalfa meal, soy meal, etc.)

3. Land Extensive, Minimal inputs. This group uses less than 75% of their land for vegetables each year and, most often, less than 50%. They rely on their rotation and cover cropping for the majority of their fertility needs.

4. Land Extensive, High inputs. These farms, again, have ample amounts of land in cover crops each year but also utilize significant N-inputs in the form of manure, compost, and purchased fertilizers and amendments.

The matrix below represents our plotting of each survey respondent based on the above criteria. Each number corresponds to a farm that returned the survey. The different colored numbers indicate the primary source of fertility inputs (green= cover crops; brown=manure/compost; orange=commercial fertilizer inputs) where this was possible to determine (some surveys provided far more complete and detailed information than others). The blue numbers indicate farms that have livestock integrated into their vegetable operation.

Heading into this SARE project, published and anecdotal evidence suggested that many organic farms use land intensely and use large amounts of off-farm fertility inputs, often in the form of poultry litter. In this fertility management plotting, it is interesting, therefore, to see that many farms have relatively ample land in which to rotate crops and that many farms rely on cover crops and on-farm manure or compost for fertility.

FIGURE 2: Farm Fertility Management Matrix
[see attached file]

Some patterns that stand out in this matrix include:

1. The tendency for farms in the Land Extensive, Minimal Input category to use more inputs as the percentage of their land base devoted to vegetable crops each year increases from left to right.

2. A significant number of farms that have ample land to rotate crop still use relatively large amounts of fertility inputs. It is worth noting that a number of farms in this category have animals integrated into their vegetable rotation (noted by blue numbers). Our assumption going into the project was that many growers farm relatively small acreages rather intensively and that the integration of livestock is relatively rare.

3. It appears that some of the farms in the lower left area of the Land Intensive, Minimal Input quadrant (based on information from the surveys only), were potentially in danger of mining (depleting) their soils given the lack of fertility inputs used.

Case Study Results

The case study farms were intended to afford a more in-depth look at overall strategies and specific fertility management practices over time. By showcasing various practices we hope to educate organic growers about soil fertility management and encourage them to develop long-term, sustainable approaches that promote soil health. As stated above, we originally planned to identify 8 farms the represent a mix of approaches such as farms that integrate animals and their manure, farms that make and use compost, and farms that rely heavily on cover crops. We also wanted the case study farms to represent a range in terms of the intensity of their land use (i.e. the length of their rotation).

Given the decision to postpone the case study portion of the project until survey results were analyzed, we were able to expand the number of case study farms from eight to twelve. The farms were selected to have farms representing each quadrant of the soil fertility management matrix developed as part of the survey analysis (see Figure 2, above). Given the number of farms that raise livestock and incorporate animal grazing into their vegetable operation among the survey respondents we selected 3 farms from utilize this approach. Among all the farms, some focus on cover crops, some on compost, and some on commercial fertilizer products. Four farms were chosen from Illinois and eight from Wisconsin.

In order to capture the spectrum of management styles existing in our survey sample, we selected farms in order to have examples in each category. Given that a land intensive, Minimal input (LIMI) approach was uncommon in the sample (and unlikely to be sustainable in terms of yields and profitability) we emphasized the other categories in terms of case-study farm selection. Indeed, as we began to collect addition information from the two farms that were in the LIMI category, we found that these growers had made changes to their operation that would reclassify them as land intensive, high inputs. As a result, we ended up with four farms in each of the LIHI, LEHI, and LEMI categories.

Our case study farms range in scale from 8 to 138 total acres (owned plus rented) with between 2 and 25 acres in vegetables in a given year. Table provides an overview of the farms in terms of scale, fertility management category, and fertility management focus.

TABLE 8: Case Study Farm Overview
[see attached file]

Initial farm visits to collect background data and update information from the mailed survey were conducted in 2008. Soil sampling began as well in the fall of 2008. The farm visits and interviews were made during the spring and early summer. Information from these interviews was added to over time through additional visits as well as email and phone communication.

We formulated a soil test protocol and made arrangements with two soil test laboratories (The University of Wisconsin Soil and Plant Analysis Lab and Dr. Michelle Wander’s lab at the University of Illinois at Urbana Champaign) to analyze duplicate soil samples from each farm. In the fall, all case study farms were sent a soil test kit including a bulb planter, plastic containers and plastic bags, soil test paperwork, detailed sampling procedures, labeling instructions, and return mailing envelopes. Each farm was directed to take soil samples from two different areas of their farm (reflecting different cropping histories). Duplicate samples were taken in order to send samples to the two labs. At the University of Wisconsin lab, a standard analysis was conducted, including pH, total phosphorous, and total potassium. At Michelle Wander’s lab, the samples were tested for particulate organic matter and aggregate stability. Eleven of the farms correctly completed the soil sampling procedure and sent samples to the two labs in 2008 and all 12 completed the process in 2009.

The most immediately obvious results of the soil tests is that many farms have excessive amounts of phosphorous and some also have excessive amounts of potassium. This lends credence to some researchers’ previous hypotheses that vegetable farms can develop excessive soil nutrients given a reliance on composted animal manures, especially poultry litter. However, many of the farms in this sample likely inherited this problem as the majority farm on former dairy operations. In at least some cases, however, it appears that growers may be continuing or exacerbating high P and K levels through their use of high P poultry fertilizer products and, in one case, high volumes of nutrient rich compost.

Examples of the case study summaries that were completed can be found in the attached document titled “Soil Fertility Management on the Intensive Market Farm.” This document also summarized the survey results.

A total of four field days were conducted; one in Wisconsin and one in Illinois in both 2008 and 2009. In the fall of 2008 the host farms were Henry’s Farm in Congerville, IL and Tipi Produce in Evansville, WI. We publicized these events to our database of growers, local newspapers, and grower groups and associations. Attendance at each was exceptional. At Henry’s Farm in central Illinois we had 30 people attend and at Tipi Produce over 60 people came.

Henry Brockman of Henry’s Farm detailed his rotation in which he keeps land fallow in hay for two year before using that land for vegetable production for two years. The fallow/hay land produces mulch for his vegetable crops, hay for livestock, and paddock space for grazing. He seeds a mixture of alfalfa, red clover and orchard grass for the two year fallow part of the cycle. During the two years of vegetable production he makes extensive use of wheat and vetch cover crops in the fall. He does not use any supplemental fertilizers and accomplishes his fertility management strategy with a minimal amount of equipment and purchased inputs. It should be noted that his fields lie, for the most part, on rich bottom land along a creek, where the topsoil is deep. A more detailed synopsis of his rotation plan is part of the case study report completed in 2009.

The field day at Tipi Produce was a great contrast to the one at Henry’s Farm. Steve Pincus and Beth Kazmar led a tour of their operation and described the many different inputs and strategies they employ based on individual crops, availability of nutrients and materials, and yield expectations. They place an emphasis on adding bulky organic materials such as plowed down cover crops, leaf compost, and chopped alfalfa. They also use some concentrated materials such as soybean meal if crops needs them. Their stated goal is to increase biological activity in their soils rather than a sharp focus on supplying NPK. In contract to Henry’s Farm, their approach relied on many more types of off-farm inputs and also required different types of machinery (fertilizer side dressers, side and rear-discharge spreaders, front end loaders, etc.).

In 2009 we held the field days at Spring Hill Community farm in northwestern Wisconsin and Growing Home CSA in north-central Illinois. These events were, again, contrasts in approach. Spring Hill has been in operation since 1989 and although the growers pleads ignorance and confusion about fertility management, they have, over time, developed goals and an action plan to enhance the season-to-season fertility management as well as long-term sustainability. In the early years this farm was an example of the type of farm that imported its fertility in the form of poultry litter from the nearby turkey industry in the area. These applications were made in a general rather than linked to specific crop needs or soil tests results. Over time, this simplified strategy has evolved into one where each of the farm’s production areas is monitored closely to follow a rotation and fertility needs are more closely monitored by crop and via soil tests. As a result, fertilizer application (still in the form of composted poultry litter but now a bagged product with a specific NPK rating) is more limited and targeted. This farm has always used cover crops but, like most farms, they have improved their integration and utilization of cover crops over time as they become more experienced. Thirty people attended the field day at Spring Hill.

The Growing Home CSA field day in Illinois featured a farm that integrates livestock into their operation and rotation. Twenty people attended the field day at Growing Home. This farm raises pastured poultry in addition to vegetables. Vegetable crops are grown in rotation following a fallow period when pastured poultry is grazed using movable pens.

This farm works with volunteers and is managed by a relatively new manager. Impressions from the field day suggest that this farm was where many other farms were when they began their operations: still learning and working to develop a coherent and effective system to manage fertility. Interviews with other growers suggest that fertility management often takes a back seat to the day-to-day pressures to plant, cultivate, harvest, and market on a highly diversified market farm. The many crops and frenetic pace of a market farm often mean that the best laid plans are abandoned. The complexity of market farms and their 30 to 50 crops also means that even developing a plan is a challenging task.

Field Day evaluations were very positive. Satisfaction responses were similar from the two field days with 73% of people rating the events “very useful” and 27% “moderately useful.” No one rated the events as “not very useful” or “not useful at all.” Participants ranged from experienced vegetable growers to beginners to university students to extension or other agricultural professionals.

We utilized the field day evaluations to gather some information and opinions on soil fertility management. We asked participants at the events about the challenges facing them in managing fertility for organic vegetables. The following is a ranking of fertility management challenges from most significant to least significant:

1-Lack of time during busy growing season
2-Rotation planning and execution
3-Uncertainty about crop needs
4-Information about amendments (tied with)
4-lack of access to equipment
5-Access to land (for longer rotations)
6-Information on cover crops
7-Interpreting soil tests
8-Access to compost
9-Access to manure
10-Access to cover crop seed
11-Access to knowledgeable people

Beginning growers were more likely to rank access to equipment and uncertainty about crop fertility needs as major challenges.

Advisory Board Results

Ongoing partnerships between growers and university researchers are especially promising. Since this grant was written, more efforts are underway to investigate organic vegetable cropping systems at both the University of Wisconsin and the University of Illinois. In practice, the advisory board was one of the more challenging aspects of this project to manage given time, distance, and expectations. A formal advisory board failed to coalesce into a permanent structure but individual growers and research have had increased, positive, and on-going interactions as a results of this project. For example, researchers in the department of Horticulture at the University of Wisconsin have broadened and deepened their pool of contacts to include small, more diversified growers in addition to the large processing conning vegetable with whom they have traditionally worked with and relied upon for input. As another example, researchers in Illinois now have access and relationships with the pool of case study farms and are in the process of developing programs and projects to build upon this initial, foundation research.

We are confident that our survey results and case studies will continue to yield valuable impacts as they are utilized for information and collaborative research/outreach partnerships. Furthermore, our case study approach appears to fit well with related and parallel efforts by others including Wisconsin SARE coordinator Diane Mayerfeld and the Midwest Cover Crops Council.

Research conclusions:

Our survey provides a unique and useful examination of the fertility practices common on vegetable farms in Wisconsin and Illinois. The results are intended to further the collective understanding of fertility management options and impacts. In addition, by building a better understanding of fertility management practices and long-term strategies, we can help direct and focus university research in ways that best meet the needs of organic vegetable growers.

A workshop and a poster on our survey results were presented at two conferences: the 2008 Upper Midwest Organic Farming Conference and the 2008 Illinois Organic Production Conference. Attendance was strong and growers are clearly interested and motivated to improve their understanding of soil fertility management.

The picture of soil fertility management on organic vegetable farms gathered via our survey is one of diversity, complexity, and uncertainty. There are clearly many, many approaches and a multitude of interacting factors to consider (scale, farm diversity, rotation, tillage, inputs, etc.).
There are certainly many viable strategies depending on soil type, access to materials, land availability, and other factors that will allow growers to improve soil tilth, adopt cost-effective means of supply fertility to crops, and reduce or eliminate practices that foster soil erosion, compaction, the excessive build-up and leaching of macro nutrients, and overall sustainability.

We were delighted with the strong turnout at our four fall field days. Fertility management is an issue of great interest but also uncertainty based on our surveys and interactions with growers. The 140+ participants at the field days learned a great deal and are clearly motivated to learn via “real case examples” of how farms build and maintain soil fertility.

The impact of our field days was magnified by the participation of an invited eOrganic videographer. Three short Internet videos were produced using material from the field days and are available for viewing at and they will soon be made available at the UW CIAS website, as well as
These videos are accompanied by written summaries of the field days as well as downloadable pdf files of the grower handouts from these events.

The soil test results from our case study farms suggest a need to educate growers and to recommend adjustments to fertility management practices so that excessive levels of phosphorous can be avoided and reduced and potential leaching issues can be mitigated. The results and interpretation of these tests provides a vital backdrop to the case studies.

Our case study approach allows us to present information in a way that allows growers to adapt and adopt those management practices that best fit their situation. There are clearly many approaches and a multitude of interacting factors to consider (such as scale, farm diversity, soil type, rotation, tillage, inputs, access to materials, etc.) when crafting a fertility management plan.

Economic Analysis

The economics of fertility management were addressed in the case studies. Growers were asked to report direct costs associated with fertility management, including the cost of cover crop seed, fertility inputs, soil tests, equipment usage, fuel, etc. Growers reported labor hours for fertility management activities such as planting and managing cover crops, spreading fertilizers and making and applying compost.

The costs and labor associated with the different soil fertility management strategies varied widely from farm to farm (see Table 9). Data was not available from all farms and some of the farms provided incomplete data. The costs reported in Table 9 represent only the direct costs for purchased inputs such as fertilizers, compost, and cover crop seed and does not include machinery use and fuel.

TABLE 9: Labor hours and costs associated with soil fertility management
[see attached file]

The smallest of the case study farms in Table 9, farm A, had the highest direct costs per acre. This can be attributed to their extensive use of relatively expensive, pelleted poultry fertilizers. Their labor hours per acre were also high—primarily because when the data was collected, they still applied most fertilizer by hand. They have since mechanized and improved the efficiency of fertilization. The farm that makes and applies large amounts of compost—farm D—had the highest labor inputs. Given the time it takes to make compost, it is not surprising that many farms make very limited amounts of compost themselves and instead import it from off-farm sources. Farm B, which obtains all of its fertility from cover crops and observes a two-year fallow period, had very low labor inputs and costs. This is in part due to the fact that the cattle that graze the fallow land on this farm are managed by one of the grower’s family members, so animal husbandry does not add to his labor demands.

Based only on this small sample, the direct costs and total hours for most growers appear relatively small. Direct costs ranged from 1-4% of gross income. Labor hours were modest for most growers. Larger farms reported more hours but usually indicated that they have employees perform at least some fertility management tasks (such as spreading compost or mowing cover crops). Smaller operators usually performed most if not all fertility management work themselves.

Ultimately, soil fertility management needs to be prioritized among a long and demanding list of daily tasks when it comes to labor management. Similarly, the costs of fertility management need to be understood to be part of the necessary workings of a vegetable farm that places significant demands on the productive capacity of the soil. While fertility management costs may be minor compared to other cost centers on a vegetable farm (labor, marketing, fuel, etc.), it was observed through the course of the field days that a significant obstacle for beginning growers is access to equipment such as tractors and implements to manage cover crops and spread manure and amendments effectively and efficiently. Clearly this represents an economic obstacle for some. In general, larger farms and growers who had been operating longer had adequate equipment that made fertility management far easier and efficient and also expanded the options they could entertain.

Farmer Adoption

This project did not have a sharply defined “farmer adoption” goal as the main intention was to gather basic information about current soil fertility management strategies and practices. That said, it was clearly the case that field day and conference workshop attendees were motivated to learn more about fertility management and desirous of adopting practices that will help their farm become more environmentally sustainable and profitable. As discussed in the following section, it would be very interest to conduct a follow-up survey to ascertain how fertility management practices have changed over time.

Participation Summary

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

As described previously, publications and outreach emanating from this project included the four on-farm field days, video footage from two of those field days, handouts and on-line descriptions of those events, a report summarizing the survey results and a series of case studies, and a longer, more detailed report on the baseline survey results.

Project Outcomes


Areas needing additional study

The grower survey collected information about research and education needs and priorities. Table 10 details the research questions deemed most important to survey respondents. The most important research questions as ranked by growers included cover cropping sequences and rotations, strategies to build soil organic matter, and the impact of cover crops on weeds, insects and diseases.

TABLE 10: Survey results on university research priorities
[see attached file]

In terms of preferred education and outreach methods, growers responding to the survey preferred on-farm field days followed by extension-style publications, 1 to 2-day workshops, and a web site devoted to soil fertility management.

One long-term benefit of this research is that it provides a foundation of “baseline” data that can be revisited in the future. For example, while two year’s worth of data was collected on the case study farms, it would be interesting to collect the same information after a period of five or more intervening years. This is especially true important in order to document whether farms can and do make progress in limiting or reducing excessive phosphorous levels but important for other reasons as well. Many farms stated a clear goal of reducing their reliance on off-farm sources of fertility or lengthening and enhancing their crop rotation to include longer fallow cycles and perennial cover crops. It would be informative to document whether such goals are reached and the growers’ assessment of the transition process, challenges, and impacts.

The same is true for the grower survey. Revisiting this pool of growers would afford an opportunity to document changing strategies, practices, perceptions, opinions, and research needs as well as to study more basic demographic and industry statistics. Funding strategies are being explored to help make both these follow-up strategies a reality.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.