Integrating Organic Soybean Production following Conservation Reserve Program (CRP) Land into Sustainable Farming Systems

2001 Annual Report for LNC99-160

Project Type: Research and Education
Funds awarded in 1999: $27,500.00
Projected End Date: 12/31/2001
Matching Non-Federal Funds: $17,500.00
Region: North Central
State: Iowa
Project Coordinator:
Kathleen Delate
Iowa State University

Integrating Organic Soybean Production following Conservation Reserve Program (CRP) Land into Sustainable Farming Systems


Four tillage methods in a randomized complete block arrangement with four replications were investigated for effects on organic soybean production following CRP land in 1999 and 2000 at the ISU McNay Farm in Chariton, Iowa: Fall moldboard plowing; Fall Kverneland® plowing; Fall and spring tillage with a Howard Rotavator®; and Spring moldboard plowing. In 2000, a full three-year crop rotation was added to each system to meet certified organic requirements. Plots were laid. All organic soybean systems yielded well above the county average in 1999 and 2000 (average of 56 bu/acre). Soil quality (organic matter carbon) returned to pre-plowing levels after three weeks. In 2001, a wet spring created conditions for lower yields of 28 bu/A, which met county averages. Economic returns in the certified organic soybeans were 180% above conventional in 2001.

Objectives/Performance Targets

  1. 1. Establish plots dedicated to organic farming research on CRP land
    2. Implement production and management regimes for opening CRP land and for weed control on conventional and organic systems on CRP land
    3. Evaluate the biological and economic outcomes of the different systems
    4. Promulgate technology transfer through demonstrations/Field Days and publications for area farmers and agricultural professionals.


Materials and Methods
The McNay Memorial Research Farm dedicated approximately two acres of a five-year old forage field (bromegrass and alfalfa) for this lomg-term project. Bromegrass predominated in the field, as is typical of CRP land in this area of the state.

Experimental Design
Forty-eight plots (four tillage treatments, three crops and four replications), measuring 30 x 60 ft. each, were laid out in a randomized complete block design in September, 1999. The initial plowing of the CRP land consisted of the following treatments: Treatment 1 = fall moldboard plowing, 2 = spring moldboard plowing; 3 = Kverneland® plowing (fall); and 4 = Howard Rotavator® (fall and spring). In 2000, a rotation of corn-soybean-oats underseeded with red clover was initiated to meet certified organic requirements. Each crop of the rotation was planted each year beginning in 2000.

Tillage and Mechanical Operations
Plots that were fall plowed in 1999 (Fall Moldboard and Kverneland-plowed) were retained as fall plowed plots in 2000 and 2001. All fall tillage for the 2001 season was accomplished by December 4, 2000. Winter rye was broadcast on corn plots with a three-point mounted spreader on October 6, 2000, at a rate of one bushel per acre to serve as a ground cover to prevent erosion and mitigate weed populations in 2001 soybean plots. The rye was mowed on May 15, 2001, but not disked until June 28-29, due to an extremely wet spring. Manure was applied to all plots going to corn at a rate of 5,000 lb/acre on March 25, 2001. 'Blaze' oats and 'Cherokee' red clover were planted on April 25, 2001 at a rate of 2 bu/ac and 12 lb/ac, respectively. Soybeans (Pioneer 9305) were planted at a population of 175,000 plants/acre on June 29, 2001. The corn variety Pioneer 35P12 was also planted on June 29, at a rate of 30,000 plants/acre. Corn and soybean plots were rotary-hoed for weed control on July 2 and July 12, and row cultivated on July 27, August 5 and August 27. Soybean plots were "walked" (large weeds removed by hand) on August 27, per local organic practices to remove any potentially staining weeds prior to harvest. Oats were harvested on July 24, 2001. A separate soybean plot was flamed on August 20. Corn and soybeans were harvested with a combine on November 6, 2001.

Soil samples (five random samples per plot) were taken on November 17, 1999, and on May 9, 2000 at depths of 0-4" and 4-8", using methods described by Cambardella (1994) for the Neely-Kinyon LTAR site. Post harvest soil sampling occurred on November 7, 2001, at the same depths. Sampling for soil, plant performance, weeds, insects and nematodes followed methods developed for the Neely-Kinyon LTAR site (Delate, 1999). Crop stand counts were taken on July 17, 2001 (18 days after planting). Weed counts (3 square meter quadrats per plot) were taken on July 17. Weed counts were also taken on August 27, 2001, in the soybean flame weeding trial. Bean leaf beetles, which are associated with the soybean staining disease complex, were sampled in soybean plots on July 23, 2001, by sweeping 20 times per plot with a15 inch diameter net. Corn borer populations were sampled by removing 3 randomly selected corn whorls per plot, and recording number of corn borer feeding holes and actual larvae on July 23. Soybean cyst nematodes were analyzed by sampling 3-6 inch soil cores per soybean plot for presence of eggs on October 19. Corn stalks were collected on October 19 for stalk nitrate analysis. Corn and soybeans were analyzed for protein, carbohydrates, fiber, and oil through the Iowa State University Grain Quality Laboratory in the Department of Food Science. A 250-gram sample of harvested soybeans was analyzed from each plot for percentage of stained soybeans (soybeans with a tan, brown or mottled appearance).

An extremely wet spring in southeast Iowa resulted in a very late planting date (June 29, compared to May 16 in 2000). Consequently, lower than normal yields were obtained throughout the region. Plant populations were reduced significantly by tillage operations in both corn and soybeans. Although there were no significant differences among treatments in corn stand counts at 18 DAP (Figure 1), there were significant differences among tillage treatments in soybean stand counts (Figure 2), with fall-plowed plots retaining higher plant populations than spring-plowed plots. It is not clear if these differences were the result of differential rotary-hoeing in the plots, or soil texture changes from spring plowing. Early weed counts in corn and soybeans demonstrated no significant differences among treatments in grass or broadleaf weed populations (Figures 3 & 4). Late season weed populations in soybean showed significantly higher levels of grasses in Rotovator‚ treated plots compared to all other treatments (Figure 5).

No significant yield differences were determined among treatments in oat or soybean plots. Organic oats averaged 62 ± 2.7 bu/ac and soybeans averaged 27 ± 5.3 bu/ac, which were comparable to county averages (Figures 6 & 7). Significantly greater corn yields were obtained in Rotavator‚ plots (113 ± 4 bu/ac) compared to the fall plowed (73.5 ± 15) and spring plowed plots (94 ± 7.6) (Figure 8).

Propane flame burning significantly decreased grass weed populations in soybean plots (Figure 9). Corn borer populations were below economic threshold levels in 2001 (Figure 10), but significantly greater damage was detected in the Kverneland plots. Bean leaf beetle populations were below 2000 levels (Figure 11), with no overall significant differences among treatments. Soybean staining, caused by bean pod mottle virus and other fungi, did not differ among treatments (Figure 12). There were no significant differences among treatments in corn or soybean grain quality in 2001 (Figures 13 & 14). There were no soybean cyst nematode eggs detected in any samples.

Soil quality analysis (Tables 1 and 2) identified that moldboard plowing released five times more particulate organic matter carbon (POM-C) than the other two tillage treatments, with pre-plowing levels at ~4.0 Mg/ha POM-C, and three weeks later , reaching ~ 20.0 Mg/ha. In the other tillage methods, POM-C was two to three times higher at that time. Soil quality parameters for 2001 are currently undergoing analysis.

Results from the CRP experiments demonstrated excellent production of high quality organic soybeans on land following CRP in 1999 and 2000. Corn and oat yields were also above average. All crops in the area suffered from a wet spring in 2001, which led to organic systems yielding similarly to county averages. We were pleased to obtain excellent yields and grain quality in soybean plots that were spring plowed as opposed to fall plowed. Spring plowing will allow for a vegetative cover during the winter and avoidance of soil erosion associated with fall plowing. Organic farmers in the Midwest, however, prefer fall plowing because of several reported reasons:

Farmers normally have more time for plowing in the fall than in the spring when other tillage, planting and compost-spreading activities occur
Fall plowing allows for a more complete break-up of soil through the freezing and thawing in winter, and
Wet springs may preclude spring plowing.

For these reasons, we will continue this experiment, using funds from USDA, in order to determine yield and weed differences in the case of poor weather in the spring. Flame burning significantly lowered grass weed populations, but there was no effect on yield. We have seeded foxtail in selected plots to monitor exact weed populations in 2002.

Current economics (2001) dictate the superior economic value of certified organic soybeans ($14/bu) compared to organic corn ($3.20/bu) or organic oats ($2.25/bu). In addition, compared with corn crop demands, soybeans can produce adequately on poorer soil, typical of CRP land. Corn yields were excellent in 2000, however, with returns for certified organic corn totaling $830/acre (before costs). Returns for certified organic soybeans in 2001 were 180% above conventional soybeans. Complete economic analysis for all crops is underway with ISU economists, Mike Duffy and Craig Chase (Chase & Duffy, 1991).

Excellent yields in 1999 and 2000 demonstrated favorable N mineralization to support corn and soybean crops, which may have increased during tillage operations. N-mineralization and nitrate-N rates remained adequate during the conversion period from CRP to crop production.

Impacts and Contributions/Outcomes

Farmers have been involved in this project from its inception. The Leopold Center for Sustainable Agriculture supported Organic Farming Focus Groups in 1998 where the idea for evaluating CRP land into organic production originated. Approximately 7,000 people were made aware at 3 Field Days from 1999-2001and presentations about the benefits of spring tillage and winter rye cover crops, in addition to other sustainable and organic agricultural practices. The farmers involved in these trials have adopted sustainable practices of using winter rye cover crops. A publication on "Growing Organic Soybeans on CRP Land" has been developed (ISU Extension Organic Agriculture Series). Overall outcomes of the entire Organic Program (the CRP project is included in all activities ) are listed below.

I. Output Indicators
Generating Basic Information
Number of research/demonstration plots established to develop sustainable/organic systems: 13
Number of research/extension publications in sustainable/organic horticulture/agronomy: 15

Number of grants to supplement research and demonstration efforts: 12
Number of producers utilizing sustainable/organic practices: 353
Number of acres in certified organic production: 150,000
Number of Community Supported Agriculture projects (CSAs) active: 35
Number of diversified or alternative community marketing systems or alliances established: 5
Number of trained or updated key agricultural professionals in sustainable agriculture: 35
Number of educational meetings, field days, workshops, one-on-one contacts, phone contacts: 268
Number of mass media dissemination and direct teaching events: 7

II. Outcome Indicators:
Percentage improvement in soil quality as a result of sustainable/organic practices: 10%
Percentage reduction of harmful contaminants (excess nutrients and toxic chemicals) in Iowa waterways and groundwater: 44%
Percentage new products (out of total market) for the value-added market: 2%
Percentage income increase for family farmers from adoption of sustainable/organic practices: (Long-range determination underway in 2001)