Demonstrating the Economic and Environmental Advantages of Legume Cover Crops to New England Growers

Demonstrating the Economic and Environmental Advantages of Legume Cover Crops to New England Growers

Summary

As integral components of sustainable agriculture, cover crops reduce erosion and control weeds. In addition, legume cover crops such as hairy vetch, vicia villosa, can reduce farmers' inputs of nitrogen (N) fertilizer. Legumes have proven to be effective cover crops in warm climates, but perceived problems have limited their utilization in New England.

In this project, we will extend information concerning best management practices for cover crops through 17 on-farm demonstrations and eight field studies on three research farms where field days will be held. Our hypothesis is that farmer concerns about insufficient establishment time, winter-killing, and increased weediness with legumes are not justified. Three years of data collected in four New England states have demonstrated the ability of cover cropping systems to reduce N, herbicide and fossil fuel inputs. By establishing on-farm demonstrations and conducting a series of extension activities, including twilight meetings, field day, workshops and information services, we will ensure that our research findings, and those of other researchers, are rapidly implemented by farmers throughout New England.

Emphasis is placed on quantifying N contribution from rates of hairy vetch as low as 20 lbs/acre, which are significantly lower than the previous recommendation of 40 lbs. Seeding rate greatly influences the economics of using cover crops and large expenditures on seed could be an important reason for the lack of adoption of cover cropping practices by many growers. Preliminary studies have shown seeding rates may be reduced without loss in vetch bioassays and N contribution. Should this be feasible throughout the region, hairy vetch/rye cover crops would be more profitable than rye alone.

A second area of emphasis in this proposed project is demonstrating to farmers the potential N contribution and weed suppression effects from winter-killed cover crops. These can be planted into in early spring without knock-down herbicides and little or no tillage.

A third area of emphasis is a comparison of N contribution and weed control from hairy vetch cover crops that are either incorporated into the soil with conventional tillage practices or mow-killed and left as surface mulches for no-till vegetable production systems. Vegetables to be grown following cover crops include beans, cabbage, squash and sweet corn.

This project continues, in part, work initiated under two 1989-91 LISA program grants It is a five state, multi-disciplinary effort involving 17 growers (conventional and organic), three land grant universities, two private agricultural extension/research and education organization, and one state department of agriculture. The total two-year budget of $276,946 consists of $152,039 in matching funds and a request for $124,907 from the Sustainable Agriculture program.

Objectives

(1) Conduct farm-scale demonstrations of hairy vetch/rye cover crops and determine regional variability of hairy vetch nitrogen supplying capacity at varying seeding rates.

Currently winter rye, Secale cereale, is the predominant cover crop used in New England. Three years of research supported by the LISA granting program, however, have demonstrated several benefits of the winter annual hairy vetch not provided by rye. Vetch has provided substantial amounts of nitrogen (N) to the soil, in some situations eliminating the need for additional N fertilizer.
Perceived problems, however, have limited the utilization of vetch and other legume cover crops in New England. Farmers have raised concerns about the high seed cost of hairy vetch, poor fall growth, winter-killing resulting in a lack of spring cover, and a fear of excessive growth in the spring being difficult to incorporate with present tillage equipment.
Hairy vetch has survived harsh winters from Connecticut to Maine and has been successfully integrated into crop rotations by some growers. Our previous research has shown similar N contribution from 20 lbs. of vetch compared to the previously recommended 40 lbs./acre. While it is not known if this N contribution holds true throughout the region, if it does, a clear economic advantage will be demonstrated over rye alone. Therefore, regional variability of N contribution still needs to be determined.

(2) Evaluate (and demonstrate to vegetable growers) hairy vetch/rye and hairy vetch/oat cover crop systems for weed suppression and nitrogen contribution with conventional and reduced tillage systems, and evaluate nitrogen movement toward ground water

To help ensure public support and to benefit from direct marketing opportunities, farms should employ sustainable agricultural practices that minimize hazards to farmers, consumers and the environment. The hairy vetch/rye cover crop has shown promise in controlling weeds when mowed and left as a mulch on the soil surface.
Our preliminary research has shown increased competitive suppression of weeds when legume residues serve as the major N source for crops. Integrated studies are needed to evaluate crop nutrition and weed management in cropping systems dependent on slow release of N from legume residues vs. rapid release from synthetic fertilizer. Reduced tillage with hairy vetch and winter killed oat (Avena sativa), and mow-killed hairy vetch/rye after rye stem elongation, have been found to reduce herbicide applications and provide some weed suppression. Further investigation of the availability of N from no-till surface mulch systems and seasonal N loss from tilled systems compared to synthetic N fertilizer are needed.

(3) Demonstrate the economic advantage of legume/grass cover crops

To encourage farmers to use alternative cover crops, clear economic advantages must be demonstrated. However, because cover crops increase profits by lowering input costs rather than increasing yields, enterprise budgets for these systems must be integrated into a whole-farm financial analysis to enable farmers to make sound management decisions regarding cover crop practices. To ensure credibility, we will use economic data collected from commercial New England vegetable farms. Finally, even if a new cover cropping system is a biological and economic success, only extensive outreach efforts will ensure widespread adoption. Therefore, as part of this project, we will convene twilight meetings, farm field days, workshops and offer access to written information and researchers in addition to the large farm-scale field plots.