Substituting Legumes for Fallow in U.S. Great Plains Wheat Production

Substituting Legumes for Fallow in U.S. Great Plains Wheat Production

Summary

Abstract
A collaboration among three state universities, three non-profit farmer organizations, and more than a dozen individual farmers, the goal of this project is to discover legumes and crop/legume systems which will effectively substitute for black and chemical fallow in the Central and Northern Great Plains. Of the 42 legume species evaluated to date, yellow-blossomed sweet clover, hairy vetch, foxtail dalea, and black lentil have shown the greatest immediate promise to create true "green" fallows production systems. Current barriers to adoption of green fallow have been: 1) developing systems which reduce the vulnerability to excessive soil water depletion, 2) relatively low-cost and adapted legume species to use, 3) crop rotations that allow reliable and cost-effective establishment of legumes, and 4) sufficient knowledge and demonstration of promising systems to both the institutional (research, extension, consultant, and conservation communities) and general farming public.

In the past year, this project has sought solutions to each of these obstacles: 1) Alternative legumes and management approaches have been found effective in transforming evaporative and leaching water loss (from black and chemical fallow) into transpirational water loss (through green fallow) at all but the driest of environments within the targeted region. Only in south and west central Kansas have green fallow systems yet to be developed which sufficiently conserve water for recropping; 2) Sweet clover remains the most widely used legume because it is inexpensive and readily available seed. Other legumes, such as black lentil, are also becoming available commercially. Both hairy vetch and foxtail dalea will require less expensive seed sources before being widely adopted. 3) The development of a wheat/sunflower/green fallow rotation holds promise in both the spring and winter wheat regions as a reliable and cost effective rotation to promote soil and water conservation; and 4) demonstration and dissemination of this project is being conducted through three non-profit organizations.

In addition, the project sponsored a conference in October of 1993 targeted at state research, extension, and conservation staff to better acquaint these public institutions of the progress make in developing feasible green fallow systems for the Great Plains.

Objectives
To demonstrate and conduct on-farm research of a cereal-legume production system in the spring and winter cereal regions of the U.S. Great Plains.

To determine through exploratory small-plot research the suitability of alternative legumes in cereal/legume production systems and then develop management systems including other locally adapted crops, and livestock, to substitute for fallow in the spring and winter wheat regions of the U.S. Great Plains.

Using cost/return data generated in legume and system comparison studies, compare both wheat enterprise and whole-farm budgets for conventional fallow versus alternative legume production systems.

Results
This project has established viable green fallow production systems for the Northern Plains spring wheat region and a wheat/sunflower/green fallow system for both the Northern and portions of the Central Great Plains region. As compared to the traditional crop production systems in these regions, the green fallow systems reduce dependency upon nitrogen fertilizer, increase and extend the period of adequate surface cover to prevent wind and water erosion, build soil quality, and increase biodiversity across fields and landscapes which prevent pest and disease outbreaks. Specific results by location can be found in the recently compiled conference proceedings.

In both North Dakota and Nebraska, the non-profits have taken the lead in organizing and conducting on-farm research of various specific components of locally adapted green fallow systems. In North Dakota, alternative legumes such as hairy vetch are being experimented with on-farm to establish reliable systems of seed production. Local produciton and distribution of the legume seed needed for green fallow would decrease overall costs of the system. Also in North Dakota, more than a dozen farmers are actively helping spread wider adoption of various green fallow techniques, including the interseeding of sunflower and the use of spring-planted grain legumes. In the winter wheat region, Nebraska farmers and researchers are developing equipment to aid establishment of interseeded legumes in row crops. Though equipment was developed, due to the unusual weather of 1993, no demonstration plots were able to be established. In 1994, a coalition of non-profit, university, and oilseed crushing industry representatives are planning a series of on-farm demonstrations of the wheat/sunflower/green fallow cropping systems.

Rotational plots continued in each of the three states to further gather legume growth, nitrogen cycling, and wheat recropping data. In addition, the project has begun a cooperative venture with NRCS to evaluate the erodability of soil from farms practicing green fallow versus neighbors that don’t. Monthly surface soil samples are being gathered across the Plains and compared at the NRCS Big Spring, Texas, lab for their vulnerability to erosion. These data should help expand the inferences about the impact of green fallow systems on the environment across the Plains as a whole.

Preliminary analyses have shown certain green fallow systems economically competitive with both black fallow and continuous cropping. Additional specific results are attached and found within the conference proceedings.

Outreach
Local field days, winter extension-type meetings, and various news articles in the popular press were the principle means of dissemination during the past year. In addition, a conference was held in Rapid City, South Dakota, on October 25/26 targeted at the research, extension, and conservation community.