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. There have been no comprehensive and detailed studies that document and compare fertility strategies across organic vegetable farms in the north central region. This project will document the soil fertility practices employed by organic vegetable growers in Wisconsin and Illinois, gather specific grower information needs and research questions, generate a set of cases studies highlighting contrasting fertility management strategies, and provide a framework for instituting organic research plots on University of Wisconsin and University of Illinois research farms. Growers will be major participants in developing, implementing and evaluating the project.

Methods will include a survey and development of case studies. Publications, field days, and workshops will be 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.

The evaluation plan will entail tracking publication requests and feedback, grower involvement, field day/workshop participation, and documenting the development of organic plots and trials at University research stations. A follow-up questionnaire one year after the project will measure changes in fertility management practices.

In this year of our project, the main goal was to conduct a mailed survey of organic vegetable growers to learn about their practices, concerns, and needs.

Objectives/Performance Targets

Objectives in 2006 included completion and analysis of a mailed survey, selection of 8 case study farms, and initial data collection on those case study farms.

As included in the 2005 SARE report for this project, the survey addressed the following aspects of soil fertility management: use of inputs (fertilizers, manure and compost), prevalence of on farm composting, length of rotations, intensity of land use, tillage, and the 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?

We sought to include both certified organic growers and growers who follow organic practices but are not certified in the survey sample. The survey was to span Wisconsin and Illinois growers.

The case study farms are intended to provide an more in-depth look at overall strategies and specific fertility management practices. By showcasing various practices and host field days, we hope to educate organic growers about soil fertility management and encourage them to develop long-term, sustainable approaches that promote soil health. We 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, 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). 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.

A key goal for the case study farms is to describe the costs and benefits of contrasting fertility management systems. We plan to monitor soil nutrient levels, percent organic matter, pH, aggregate stability, and other characteristics over a three-year period on 8 farms.

Accomplishments/Milestones

In order to accomplish the mailed survey, it was necessary to gather information and databases from a number of organizations and individuals. Following our project methods, we also pre-tested the survey among a group of University colleagues as well as organic farmers serving as advisors to the project.

Drafting the survey with input from several collaborators and then pre-testing it with our grower advisory group was accomplished 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 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%. (We may continue database cleaning efforts and, if so, anticipate a final response rate between 50% and 60%).

Analyzing the survey data began in the Spring of 2007 and continued until January 2008.

The following table summarizes the demographics of survey respondents:

Table 1: Respondent Demographics and Characteristics

Variable Number Percent
Gender
Males 61 70%
Females 26 30%

Age grouping
1-25 14 16%
26-49 28 33%
50-56 30 35%
57-older 14 16%

Education
H.S. degree 6 8%
Assoc. degree 3 4%
Some college 12 16%
College degree 41 53%
Graduate or
Prof. degree 14 18%

Years Farming
1-5 19 22%
6-10 16 19%
11-20 24 28%
21 or more 26 31%

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%). One question the survey sought to answer was how intensively growers use their land. Our assumption going in 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.

Nearly 55% of the growers used between 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. This ratio was one factor used to help determine our farm management matrix and the ‘intensive’ or ‘extensive’ use of land. The majority of farms (55%) were generating up to $20,000 from the sale of veggies, melons, herbs and flowers. Surprising, the majority of farms (60%) are extremely diverse with vegetable, livestock, and other additional crops (see Figure 1).

Table 2: Farm Characteristics
Variable Number Percent
Farm Size
less than 3 acres 32 36%
3-6 acres 15 17%
7-15 acres 18 21%
15-24 acres 6 7%
25 and more acres 17 19%

Ratio — Acres in vegetables/
Acres in vegetables & cover crops
0-.25 12 14%
.26-.5 23 26%
.51-.75 13 15%
.75-1 40 46%

Gross income from sale of veggies, melons, herbs & flowers
Up to $20,000 46 55%
$20,001 to $50,000 14 16%
$50,001 to $100,000 14 16%
$100,001 to $200,000 7 8%
$200,001 to 500,000 3 3%

Soil Types (Note: survey respondents could list more than one type)
Clay 13 15%
Clay loam 49 56%
Silt loam 39 44%
Loam 13 15%
Sandy loam 28 32%
Sand 7 8%

Figure 1: Farm Diversity
[Figure would not paste into on-line report]

Table 3 helps characterize the respondents in terms of practices and common farming 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, was only reported by 3% of the respondents.

Table 3: Practices used in Vegetable Operations
Practice Number Percent
Permanent raised beds 12 14%
Temporary raised beds 32 37%
Row crop system 67 76%
No till 3 3%
Permaculture 13 15%
Living mulch 24 27%
Plastic mulch 37 42%
Mulch (hay, straw) 70 80%
Interplanting 30 34%
Multicropping 41 47%
Contour planting 24 27%

Some additional interesting statistics from the survey include:

1. 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.”

2. Forty seven percent (47%) perceive that micronutrients are in inadequate supply on their farm (compared to 26% in regard to nitrogen and 17% in regard to phosphorous and potassium). 24% felt that phosphorous and/or potassium are in excess supply in their soil (compared to only 5% in regard to Nitrogen and 18% in regard to micronutrients).

More detailed results, analysis, and discussion will be included in the 2007 SARE annual report.

Selecting the case study farms was postponed in order to utilize the survey data to inform the process. We decided that it would be most useful and relevant for the case study farms to accurately represent various fertility management scenarios in the region. We also wanted to try to engage in partnerships with farmers outside our normal group of contacts. Therefore, we decided to wait until the surveys were tabulated and analyzed before moving forward on the case studies in 2007.

Impacts and Contributions/Outcomes

Our survey represents a unique and useful examination of the fertility practices common on vegetable farms in Wisconsin and Illinois. Presentations, posters, and written research reports are being prepared in order to share the information we gather with researchers, farmers, and other interested stakeholders. With this information we will also select a representative mix of farms on which to conduct case studies over the next two years.

We intend for the survey results to further our collective understanding of fertility management options and impacts. Further, we hope that by highlighting various types of “best management practices” that more growers will adopt longer rotations, expand efforts to increase soil organic matter, adopt more cost-effective means of supply fertility to crops, and reduce or eliminate practices that foster soil erosion, compaction, and the excessive build-up and leaching of macro nutrients.

In addition, by building a better understanding of fertility management practices and long-term strategies, we plan to help influence the adoption and examination of various practices on University-based research plots.

Collaborators: