Grain farmers of Spokane and Lincoln Counties, WA, want to improve soil health on their land without compromising cash crops that are proven for this area, which depends heavily on winter precipitation. This project was a feasibility study for cover- and companion crop mixes for use in this dryland cropping zone. So far, seeding cover crops in the spring in place of fallow, results in excessive loss of soil moisture so that getting a crop germinated that fall has proven risky. Growing companion crops together with a cash crop shows potential for reaching the desired goal. However, many questions remain to be answered by future research.
Dryland grain farmers in Lincoln and Spokane Counties, WA, want to improve soil quality on their farms. In 2011, farmers who attended a WSU (Washington State University) Extension workshop were inspired and intrigued by the success of Midwest farmers in using cover crop cocktails for this purpose. A group of innovative growers developed the goal of learning how to include a cover crop or companion crop in their rotation to raise soil organic matter levels, break disease cycles, suppress weeds, penetrate soil compaction layers, and improve soil fertility by fixing atmospheric nitrogen. In addition, they want to make this system work with the winter precipitation (Mediterranean climate) of the area.
We used the following definitions.
Cover Crop – a crop grown to feed/benefit the soil. No harvested material leaves the field, it is incorporated by tillage or sprayed down.
Companion Crop –a cover crop grown together with a harvested/cash crop
Cover Crop Cocktail – a mixture of several species as cover crop. It may include warm and cool season species, grasses to provide biomass, legumes to fix atmospheric nitrogen, and broadleaf crops with a tap root to penetrate hardpan layers.
Cover crops, also known as green manure, were grown commonly in eastern Washington prior to the advent of synthetic fertilizers in the 1940’s. One of the farmers in the group had childhood memories of growing yellow sweetclover (YSC) on their farm as a green manure. Widespread use of this species ended when widespread insect damage in the YSC made it impractical to grow (G. Dobbins. April 2011. Personal communication).
Subsequent local research into cover crops has had varying results. Walter Goldstein reported that crimson clover showed promise as a cover crop species (W. Goldstein. 1986. WSU PhD dissertation). In an on-farm project, Lincoln County farmers found that Black medic was not sufficiently competitive as a companion crop (J. Jahn and C. Carstens. 1992. Personal communication). In testing a wide array of cover crops at Pullman, USDA (United States Department of Agriculture) researchers concluded that nothing was economic (D. Huggins. 2011. Personal communication).
None of this research, however, looked at multi-species cover crops. The advantage of using a cover crop cocktail is twofold. Different species provide different soil benefits, and if one species in the mix fails to grow, others will take its place.
The local farmer group recognized that successful developments in Midwest states, which have a summer rainfall pattern, would not necessarily translate directly to eastern Washington where most of the annual precipitation occurs in the winter months. For example, an organic farmer from Big Sandy, Montana, has developed a system for growing all his fertilizer in the form of cover crops and companion crops (including yellow sweetclover) on his 4,000 acre dryland farm. However, although his total annual precipitation is similar to Davenport, WA, June is typically the wettest month on his farm. This enables him to grow warm season species that do not thrive in eastern Washington (R. Quinn. July 2008. Personal communication).
The model for this project was that the farmer collaborators developed the ideas for which cash cover crops to try, and they grew a demonstration block on their farms. The Extension professionals repeated these tests in randomized, replicated strips (about 18 ft wide by 200 ft long) on the WSU Wilke Research Farm at Davenport, WA.
The project began (prior to funding from Western SARE) in the spring of 2011. While interest in the project from around the region has been high, we do not yet have “proven recipes” to share with other growers. It is truly a work in progress.
While the Wilke Farm and most of the farmers in the group use direct seeding/no-till farming, we believe that these cover crop methods should benefit any type of farming system.
Experiment with cover crop cocktails and companion/intercropping to develop mixtures and places in the local dryland grain rotations where they benefit soil health and moisture retention.
In all the following trials, we took soil tests each season to track changes in soil moisture, organic matter, and nutrients.