Soil Fertility Strategies on Organic Vegetable Farms

Soil Fertility Strategies on Organic Vegetable Farms

Summary

Organic growers in general—and organic vegetable growers in particular—rank soil fertility as a top research priority. This project is documenting the soil fertility practices employed by organic vegetable growers in Wisconsin and Illinois, gathering specific grower information needs and research questions, generating a set of cases studies highlighting contrasting fertility management strategies, and providing a framework for instituting organic research plots on University of Wisconsin and University of Illinois research farms. Growers are participants in all phases of the project, including development, implementation, and evaluation.

Methods include a survey, case studies, and the development of an advisory panel to interact with University researchers. Publications, field days, and workshops are being used to communicate results and solicit feedback.

Outcomes will include 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 increasing organic research acreage on University research farms.

Objectives/Performance Targets

In this year of the project (2008), the main objectives were to work with 12 case study farms to collect data, hold two on-farm field days, and prepare a report on the results of the grower survey (completed in 2006/2007). In addition, we planned to further our work to integrate the information we are learning and the direct perspectives of growers into ongoing planning and programming at both the University of Wisconsin and the University of Illinois.

Accomplishments/Milestones

As reported in 2007, we have selected 12 case study farms following our survey of organic vegetable farms in Wisconsin and Illinois to serve as examples of different fertility management strategies. These farms were selected following our analysis of the survey data we collected in 2006/2007. In analyzing the survey data, we developed a matrix for the purpose of categorizing farms into 4 different fertility management groupings. These are:

Land intensive, high inputs (LIHI),
Land intensive, low inputs (LILI),
Land Extensive, high inputs (LEHI), and
Land extensive, low inputs (LELI)

In order to capture the spectrum of management styles existing in our sample, we selected farms in order to have examples in each category. Given that a land intensive, low input (LILI) approach was uncommon in the sample (and not 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 LILI category, we found that these growers are making changes to their operation that would reclassify them as LIHI. We now have 4 farms in each of the LIHI, LEHI, and LELI 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.

During the Spring and early Summer, each case study farm was visited once for the purposes of an interview that updated the information already on hand about these farms (from the mailed survey) as well as to collect additional information, opinions, and questions regarding fertility management. The information from these interviews will be added to over time and become the foundation of the case study write-ups that will be completed in 2009.

During the year 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 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 tests to be conducted include particulate organic matter and aggregate stability. Eleven of the farms correctly completed the soil sampling procedure and sent samples to the two labs. We plan to take Spring soil samples from the one farm that failed to complete the task in the fall.

The UW lab completed their tests and analysis and returned results to us in November. Michelle Wander’s lab has not completed their testing and reporting. Preliminary observations from the soil tests reveals that many farms have excessive amounts of phosphorous and some also have excessive amounts of potassium. This validates some researchers hypothesis that many vegetable farms can develop excessive soil nutrients given a reliance on composted animal manures, especially poultry litter.

In the fall of 2008 we held two on-farm field days at two of the case study farms: 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 complete and detailed synopsis of his rotation plan will be part of the case study report to be 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.).

Field Day evaluations were conducted and 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 based on 48 survey respondents:

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. We plan to gather similar information during the field days in 2009 as well as probe these issues with our set of case study farms. In particular, we are curious about how growers go about rotation planning and why plans are sometimes not executed, gathering information about fertility management labor and comparisons of different strategies in terms of hours required, and the type and sources of information preferred to address some of the above challenges (such as information on amendments and crop nutrient needs).

Work continues on drafting and submitting a peer-reviewed article based on the results of our grower survey in 2007.

[To view figures from this report, contact the NCR-SARE office at ncrsare@umn.edu]

Impacts and Contributions/Outcomes

We were delighted with the strong turnout at our two fall field days. Fertility management is an obvious issue of great interest and uncertainty based on our surveys and interactions with growers. Over 90 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. We are confident that our case study approach will yield valuable information and be well received by both experienced and beginning growers. Furthermore, our case study approach fits well with related and parallel efforts by Wisconsin SARE coordinator Diane Mayerfeld as well as Midwest Cover Crops Council.

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 http://www.vimeo.com/2312395 and they will soon be made available at the UW CIAS website, www.cias.wisc.edu as well as .

These videos will be accompanied by written summaries of the field days as well as downloadable pdf files of the grower handouts from these events.

As noted in our 2007 report, as we continue to delve into the case study farms, we intend for this project to highlight various types of “best management practices.” 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 potential leaching of macro nutrients (especially phosphorous), and overall sustainability.

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 potential leaching issues can be mitigated. The results and interpretation of these tests will provide a vital backdrop to the case studies we will be preparing and any recommendations on “best management practices” that will be forthcoming from this project. In 2009, we plan to closely examine the case study farms historical fertility management practices and repeat our soil tests procedure in order to better understand the cause of excessive macronutrients and ways to improve this situation.

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

Collaborators: