Project Number: 2090-21000-034-03-I
Project Type: Interagency Reimbursable Agreement
Start Date: Oct 1, 2015
End Date: Aug 31, 2019
Organic farmers use legume cover crops to provide nitrogen to subsequent crops and other important ecosystem services. Legume cover crops can help farmers reduce soil erosion, improve soil health, and avoid excessive applications of phosphorus from manure or compost. Despite the array of benefits that legume cover crops provide to organic farmers, legume cover crop breeding and cultivar development research has been extremely limited. Due to a lack of germplasm development efforts, most farmers use unimproved varieties or seed that is not adapted to their farm or region. Moreover, winter legume cover crops suffer late maturity, seed dormancy, winter-kill, and indeterminate flowering. We will implement an interdisciplinary, multi-institutional research and extension project focused on improving legume cover crops for organic farmers. Our project addresses knowledge gaps associated with legume cover crop germplasm performance (e.g. establishment, growth and development, biomass accumulation) and ultimately will increase availability, economic benefits, and adoption of legume cover crops. The long-term goal of this project is to maximize legume cover crop performance, profitability, and adoption through participatory germplasm screening, in field selection for elite lines and genetic marker development.
We will regionally screen and select legume cover crop germplasm, segregating populations, breeding lines, and varieties for improved performance and targeted agronomic characteristics of particular interest to organic farmers at sites across the U.S. In addition to organic research station sites around the country, 10 USDA-NRCS PMCs and 10 organic farms will participate in variety evaluation and selection, respectively. The locations selected for this project represent a range of environmental conditions and organic cropping systems found throughout the U.S. In tandem with screening and breeding efforts in MD, NC, NY, TX, WA, and WI, we will employ participatory variety trailing and breeding. Participatory variety trialing will bring farmers to sites of germplasm screening to identify genotypes that meet their needs. There, through focus group discussions, farmers can share information about the cover crop qualities that best suit their agricultural systems. Participatory breeding will also generate varieties. After 10 organic farmers establish segregating populations on their farms, they will have multiple opportunities throughout the cover crop season to observe and select the best individuals. Specifically, for winter peas, we will identify suitable existing cultivars, accessions, and germplasm releases from breeding programs (e.g. the USDA-ARS Grain Legume Genetics and Physiology Research Unit, ProGene, and the University of Wyoming). There are approximately 15 commercial winter pea cultivars available. Additionally, there are 63 unique winter pea PI lines in the USDA National Plant Germplasm System (NPGS) Pisum collection. Regional trialing locations will plant and evaluate replicated trials of germplasm with large amounts of seed available. Testing locations will be chosen which are representative of the region and provide some amount of low temperature stress, but not extreme. The experimental design will be an alpha lattice (or RCBD) with 4 reps. Plot size will be approximately 6 x 1.5 m. Inoculated (Rhizobium leguminosarum) seeds will be planted at a rate of 100 seeds per square meter. Seed from the USDA germplasm system is available in limited quantities and will need to be increased. In order to maximize seed production and minimize the time before replicated trials can be conducted with this material, seed will be increased in a counter-season nursery in the Southern Hemisphere (Plant Research NZ, LLC, Lincoln, New Zealand). By utilizing the counter-season, we will have enough seeds to begin field evaluations and selections at multiple locations in year 2. During the seed increase phase, accessions will be evaluated for potential use as a cover crop. Selections for inclusion in Year 2 trials will be based on traits including leaf type, internode length, and biomass production. The existing autumn-sown pea breeding program at USDA-ARS will initiate a new project that will specifically breed winter peas for use as a cover crop. Previously, existing F2’s and F1’s from new crosses were grown in the breeding nursery.