Cover Crops and Cover Crop Mixtures
Mixed cover crop in October near Amsterdam, MT
Cover crops can potentially improve subsequent crop yields through enhanced soil health and reduced soil erosion, cut fertilizer, herbicide and pesticide costs, and protect water quality, all of which can increase farm sustainability. The potential to fulfill these benefits may be increased by using mixed rather than single species cover crops. Although there has been substantial research on single species cover crops, research on mixed species cover crops is in its infancy, so many of the potential benefits are hypothesized rather than known. Species can be selected for desired traits such as fixing nitrogen, producing large amounts of root and shoot biomass, or scavenging resources from deep soil layers. Because each crop in a species mix may respond differently to soil, pest and weather conditions, mixtures may increase cover crop survival, ground cover, biomass and nitrogen production, weed control, duration of growing season, range of beneficial insects attracted or pests deterred and forage options.
Current Research Overview and Updates
Our 4 year study (2011-15), funded by Western SARE, was a collaborative project with Montana producers to look at cover crop mixtures as a partial replacement of fallow in rain-fed cropping systems. We have continued a portion of that study with funding from the Montana Fertilizer Advisory Committee. We are studying how combinations of plants or plant functional groups might change specific soil quality indicators, and determine optimal timing of growth for water use and soil improvement. The study will help provide information on plant functional groups to help farmers when selecting cover crop seed mixtures.
This study tests the effects of cover crop mixtures, planted in the spring and terminated in June, on crop yield, soil quality, and water availability and subsequent wheat yield and quality. We are comparing seed mixes containing either two, six or eight species from four functional groups against fallow and a single species cover crop. The functional groups address soil quality issues specific to farming in the northern Great Plains. They include species that;
- fix nitrogen to reduce nitrogen fertilizer inputs
- provide ground cover to reduce weed establishment and evaporation
- have deep tap roots to minimize compaction and move nutrients upwards
- have fibrous and extensive root systems to add soil carbon and promote aggregation
Soil quality has been assessed with measures of soil nutrients and mineralization rates, characterization of the microbial community and mycorrhizal fungi, and physical parameters including measures of temperature, compaction and aggregation. The study has included both plot-scale and on-farm field-scale studies.
SURVEY: In the winter of 2015 we sent a survey to 500 Montana producers to learn of their experiences and perspective about mixed species cover crops. The major findings are reported here (15-page report with graphs). A short College of Agriculture report is also available (4 pages, no figures), as is the survey.
RESULTS: Our results are available in the final report and being presented at field days, workshops with presentations by farmers and researchers, through documents, radio, streaming video, grain grower newsletters and this web page (see link below).
The collaborators on the WARE study were: Perry Miller, Clain Jones, Cathy Zabinski, and Meg Housman, all from the Department of Land Resources and Environmental Sciences at Montana State University; Susan Tallman, USDA-NRCS Agronomist; Jay Norton from the Department of Ecosystem Science and Management at University of Wyoming; Jane Holzer with the Montana Salinity Control Association; and Carl Vandermolen, Herb Oehlke and Chad Doheny, producers.
For More Information
- Cover Crop Survey
- Presentations, videos, publications and reports
- Links to related resources