Multipurpose Brassica cover crops for sustaining Northeast farmers

2004 Annual Report for LNE03-192

Project Type: Research and Education
Funds awarded in 2003: $158,570.00
Projected End Date: 12/31/2007
Matching Federal Funds: $113,673.00
Region: Northeast
State: Maryland
Project Leader:
Dr. Ray Weil
University of Maryland

Multipurpose Brassica cover crops for sustaining Northeast farmers


This project is designed to conduct on-station and on-farm research investigating multiple benefits from cover crops, with a special focus on Brassica species, in order to accomplish two related goals. First, the research has the potential to demonstrate how multiple benefits can make these cover crops profitable enough to encourage wider adoption of this sustainable farming practice by farmers in the NE. Second, the process used to conduct this research will empower and will encourage farmers to conduct their own research on their own farms, empowering them to generate objective answers to their own questions about cover crops and other farming practices. The project aims to achieve these goals through four on-station field experiments that investigate a range of cover crop species, management practices and possible mechanisms behind some of the beneficial effects, combined with on-farm research conducted by about 15 farmers. The farmer-research will address simple, focused questions about profitably fitting cover crops into specific farming situations. Results from at least 10 on-farm and 4 on-station experiments will contribute to a regional database on Brassica cover crops. This database will evaluate the practical effectiveness of various Brassica cover crops, grown alone or in mixtures, in capturing residual nitrogen before it can leach away, in providing lower cost and more sustainable alternatives to replace deep tillage for compaction alleviation, to replace fumigation for nematode and fungal disease suppression, and to replace some herbicides and tillage for weed control. Extension educators, farmers and project personnel should be able to use these results to promote appropriate and profitable cover crop practices. Project personnel will work closely with farmers and county extension educators to develop farmer research interests and skills. Farmer participants will share their results and methodologies with other farmers, researchers and extension personnel via newsletters, conferences, presentations, field days, on-farm twilight tours, and discussion groups sponsored by Cooperative Extension and Future Harvest- Chesapeake Association for Sustainable Agriculture (FH-CASA). The project will work with farmers to use the experience and lessons learned to produce a user-friendly, visually-oriented guide to conducting on-farm research this guide will build upon several farmer research publications already in existence. The project aims to develop skills, experience and interests that lead to continuation of farmer initiated research activity and research support groups even after the project-funding period.

Objectives/Performance Targets

  1. 1. The project aims to reach some 400 horticultural and grain crop farmers, interest 40 of these farmers in transitioning to the use of cover crops for two or more of the benefits demonstrated by the project research, and empower 10 to 15 of the farmers to conduct Brassica cover crop research trials on their farms.

    2. Six of the farmers who participate in the design and implementation of trials to evaluate multiple benefits of Brassica cover crops on their farms will collaborate in the development of two farmer research guide booklets and participate in continuing farmer-to-farmer support of on-farm research.


This project requires that information on the Brassica cover crops be gathered and/or new information be generated by field research before we can provide practical information and recommendations to farmers. However, while we are gathering and generating new information, we are also reaching out to farmers with our preliminary results to generate interest in possible uses for the Brassica cover crops that are new to our region. We are also using the new (Brassica) cover crops as a vehicle to interest and empower farmers in to conduct their own research that provides reliable answers to their own questions about farming practices. During the first 8 months since the project funding began in May, 2003, we established field experiments on four different experiment stations and worked collaborated with 5 commercial farmers in conducting 8 replicated on-farm experiments.
Each on-station experiment is designed to investigate several of the proposed Brassica cover crop benefits, as well as to develop or validate information on the practical management of these cover crops (such as planting dates and seeding rates). Most of the on-farm experiments are aimed at evaluating one specific cover crop function that addresses a problem identified by the farmer. The main functions under investigation are:

1. alleviation of subsoil compaction
2. suppression of plant parasitic nematodes
3. reduction of weed pressure
4. improvement of soil structure
5. capture excess N in fall to prevent nutrient pollution
6. enhanced nitrogen cycling to crops

Because each experiment is focused on a different set of cover crop functions, not all of the Brassica cover crops we are working with are represented in each study. However, in August 2004, we established at each on station site a second experiment that does allow us to compare forage radish, rapeseed, rye and no cover (weeds only) at all four sites.
We have now collected two years (effectively, up to 14 site-years) of data on the fall biomass production of five different Brassica cover crops, plus several combinations of Brassicas with non-Brassica cover crops. For the cover crops with fleshy taproots, we measured the biomass of both the shoot and the fleshy taproot (which accounts for most of the root system dry matter, although very little of the root length or surface area). Data collection is complicated by the fact that some of the studied cover crops are killed by freezing in winter (oilseed radish, forage radish, mustard, oats), while others are not killed (mainly rapeseed and rye), and therefore continue to grow in spring before summer cash crops are planted. We have begun to analyze the shoot and root biomass for N uptake in fall and have taken soil cores to 150 cm deep to study the degree to the cover crops have taken up residual nitrate from soil the profile. We have completed some preliminary assessments of nematode and weed suppression at two sites and have collected data on cover crop effects on subsoil water supply at three sites. The data show some dramatic and highly significant effect by Brassica cover crops on nematode populations in summer, weed cover in spring, and N uptake from the profile in fall. Although we had some excellent stands of the cover crops and some bin-busting yields of soybeans following them, the excellent rainfall distribution in the 2004 growing season meant that the influence of the cover crops on subsoil water in summer and soybean yield was statistically significant at only the sites with sandy soils. At the no-till Hayden Farm site, there was a 7 bushel/acre yield advantage (about a 10% increase) for soybeans growing after oilseed radish or forage radish as compared to soybeans following mustard, rape or no cover. At the conventionally tilled LESREC site, soybeans growing after any of the cover crops tried yielded significantly more than those after no-cover crop. At all sites, forage radish (‘Daikon’) grew the fastest in fall and was very competitive against weeds. Even after the forage radish stand was winter killed, strong suppression of spring weeds was event.

In addition to newsletter updates on the cover crop research, we held two sessions in the annual Farming for Profit and Stewardship conference put on by Future harvest and Maryland Cooperative Extension in January 2004, one on the Brassica cover crops themselves and the other on the potential for farmer research. The response at both was excellent, with 65 farmers requesting further information or asking to collaborate on research on their farms. Among the participants at the farmer research session, 52 farmers filled out and returned a questionnaire about doing research on their farms, of which 43 (87%) said they currently use cover crops to some degree and 48 (93%) answered “yes” to the question: “Would you be interested in learning how to conduct your own experiments on your farm?” We worked with 7 of these farmers to help them make detailed plans for Brassica cover crop research on their farms addressing one or more of the problem areas listed above that Brassicas may have the potential to ameliorate. To 60 farmers with whom we could not work directly this year, we sent a package of seed (usually enough forage radish or rape to seed about 1/3 acre) and a request that they fill out a brief form to report what they did with the seeds and their observations on their performance. By December 1, we had received 13 of these completed forms. Also in December, we participated in the annual Agriculture and Natural Resource agricultural extension in service training where we presented ideas on the difference between farmer research and scientist research done “on-farm”, as well as on how county extension agents can foster farmer research. Some 20 extension personnel participated in this session.

We began our outreach efforts with the publication of a preliminary fact sheet summarizing what we know or expect about the Brassica cover performance in the mid-Atlantic region. We also ran a story in the September Future Harvest newsletter which reached some 300 farmers (more than half way toward Milestone #1). In it, we call for “A Few Good Farmers” to join us in studying these cover crops and learning about farmer-research. To date we have received over 20 responses requesting more information by phone and email. Of these, 13 farmers expressed interest in participating next fall in on-farm research with the Brassica cover crops. Thus, we are about 20% of the way to Milestone #2. We are scheduled to participate at the Farming for Profit and Stewardship Conference in Hagerstown Maryland in January 2004 where we will conduct a workshop on the Brassicas and attempt to initiate a farmer research circle to address the performance targets. A questionnaire will also be distributed at this winter farmer conference. Several presentations by our Brassica cover crop team have also been scheduled at winter workshops at the request of extension agents.

Impacts and Contributions/Outcomes

Our project has already stimulated interest in Brassica cover crops and farmer research among a wide diversity of farmers and extensionists. In March 2004, the largest farm newspaper in our area, The Delmarva Farmer, ran a front page story devoted mainly to our investigation the potential benefits of Brassica cover crops. In the first year and a half of the project, approximately 40 farmers that we know of in Maryland, Pennsylvania, Delaware, Virginia and West Virginia have begun to experiment with Brassica cover crops. The State of Maryland has now included Brassicas in its cover crop support program aimed at reducing nitrogen loading to the Chesapeake Bay. The September 15th planting cut off for Brassica in that program is in part based on our experience in field experiments. The input provided to the research process varies among the farmers who are collaborating with our project, but in most cases the trial aims to address a question posed by the farmer (e.g. can the Brassicas help me with my soil compaction problem? nematode infestation? weed pressure? etc). While it is too early in the project to report on the farmer-adoption and research outcomes, we can report that in year 1, five farmers tried Brassica cover crops in collaboration with our project, and three of these suggested the basic objectives of the experiments on their farms. In year 2, we worked closely with seven farmers, all of whom originated the basic objectives of their experiments. At least 13 (but probably twice that number) additional farmers are experimenting on their own with Brassica as a result of seeds we provided. Most of the later are not conducting replicated trials. Next year should see the initiation of one or more farmer research support groups and the beginning of development of farmer research guide materials.

Although our research on this topic is continuing, our results indicate that the Brassicas are capable of rapidly taking up large amounts residual soil N in the fall if planted earlier than mid September. With tissue N concentrations ranging from 2.0 to 3.0% and dry matter ranging up to 6,000 kg/ha by late fall, the fall N uptake potential is much larger than rye, which is the standard N capture cover crop in our region. Using soil cores taken to 150 or 180 cm deep, we have seen that the Brassicas rapidly depleted the soil profile of soluble N. However, our investigation of mineral forms of N in the upper 30 cm of soil in March, May and June failed to account for the N taken up by the cover crops, killed by frost in January (radishes, mustard) or by tillage or herbicide in April or May (rye as well as rape). Further research will be conducted to attempt to account for the fate of this N.

The optimum planting method for our region appears to be drilling seed in mid to late August. This practice is most practical for diversified vegetable growers. Most grain farmers in the mid-Atlantic region do not plant cover crops until several weeks later (mid-October following corn harvest, and mid-November following soybean harvest). Grain farmers, who typically account for much larger acreage than the vegetable growers, have expressed interest in finding alternative approaches to planting the brassica cover crops. They have suggested either flying the seed on into standing corn or soybean crops before mid September, or planting the covers early in spring, instead of in fall. In the coming spring, we plan to work with several farmers who want to try planting one or more of the Brassicas at spring “green up” time (late March) and kill them just before planting soybeans around June 1.

Two large scale farmers also collaborated with us to fly replicated strips of forage radish seed into standing corn crops in mid August. Both of these farmers were interested in the soil compaction effects of the forage radish and both used the same airplane applicator flight to seed three widely spaced strips 300 feet long in their respective fields of corn. One of the farmers wants to avoid having to deal with killing a cover crop in the spring, and was therefore attracted by the winter kill characteristic of the forage radish. In some cases, the “aerial seeding” has resulted in very good stands that eventually produced 50 to 80% as much dry matter as the August drilled covers. In other cases, especially when seeding was done too far ahead of crop senescence, the Brassica understory seedlings suffered from lack of light, resulting in thin stands, poor initial growth and a low root to shoot ratio that might compromise the cover crops’ ability to improve soil quality. In fall 2004, we also implemented “aerial seeding” in our four on-station experiments by spinning the seed into soybeans at leaf yellowing.

In summary, although there is need for much more research on the influences of the Brassica cover crops and on their practical management, we believe we are stimulating interest in the Brassicas among regional farmers and are beginning to make progress in empowering farmers to do their own research.


Steve Groff

[email protected]
Cedar Meadow Farm
679 Hilldale Road
Holtwood, PA 17532
Office Phone: 7172845152
John Teasdale

[email protected]
Weed Scientist and Research Leader
USDA/ARS, Sustainable Agric. Systems Lab
Wallace Agric. Research Center
Bldg. 001 Room 245
Beltsville, MD 20705
Office Phone: 3015045504
Sandra Saardanelli

[email protected]
IPM Coordinator and Nematologist
University of Maryland
H. J. Patterson Hall, Rm. 2105
University of Maryland
College Park, MD 20742
Office Phone: 3014057877
David Almquist

[email protected]
County Extension Director & Extension Educator, Ag
Harford County Extension Cooperative Extension
Caragh Fitzgerald

[email protected]
Extension Educator, Agriculture & Natural Resource
Howard County Cooperative Extension
Office Phone: 4103132710