Maximizing Nitrogen Fixation in Cold-Hardy Hairy Vetch
Cool season cover crops used in organic systems have the capacity to improve soil health and nutrient contributions, if productivity and biomass can be optimized. Leguminous cover crops, in particular, provide nitrogen via biological nitrogen fixation (BNF), reducing the need for inputs such as manure, which can lead to overloading of bound phosphorus. The legume hairy vetch (Vicia villosa) is widely used as a winter annual cover crop in the Midwest because of its cold-tolerance and weed-suppressive effects. Although known to have among the highest BNF rates of common cover crop legumes, hairy vetch adoption has been limited in cold regions by management challenges, including weediness, termination difficulty, and inconsistent winter hardiness. Hairy vetch BNF also varies across landscapes, owing partially to the fact that recommended rhizobia inoculant strains commonly applied at planting may not be well-adapted to their environment. Cold growing conditions hinder BNF, but fortunately, in areas where hairy vetch was previously grown, there are indigenous populations of rhizobia that are well-adapted to their climatic conditions. This study will identify rhizobia strains best suited for symbiosis with two new cold-hardy hairy vetch ecotypes in the climatic conditions of the upper Midwest. Rhizobia adapted to severely cold climate conditions will be collected from the northernmost University of Minnesota field station. Two cold-hardy ecotypes of inoculated hairy vetch will be grown at 10°C, to reflect fall temperatures in the upper Midwest. Plants will be inoculated with rhizobia strains sourced from across a climate gradient, including the newly collected strains from northern Minnesota and existing strains from our extensive rhizobia collection. Plant BNF capacity and nodule number will be measured to determine efficiency of each rhizobia strain. I will disseminate my findings via a scientific publication and a talk at an organic-grower focused conference, with the potential action outcome of farmer inoculation strategy modifications.
Project objectives from proposal:
The goal of this project is to produce inoculant information for hairy vetch that can be used in cover cropping recommendations for farmers in the upper Midwest, especially those in USDA plant hardiness zones 3 and 4, in order to meet prescribed organic practices outlined in the USDA National Organic Program.
Learning outcome 1: Organic researchers and extension agents will have access to information about legume host-rhizobia relationships, and optimal inoculation strategies for hairy vetch.
Learning outcome 2: Approximately 50 farmers will learn about the role of rhizobia in improving hairy vetch BNF during a field day. An additional 50 farmers will learn this information at an organic farming conference (MOSES or Minnesota Organic Conference).
Action outcome 1: Around 50% of growers from the field day and conference presentation will try using rhizobia inoculants to improve hairy vetch, or other legume, performance in the coming season.
Action outcome 2: The published peer reviewed article will provide a foundation for future research on hairy vetch cultivation in the upper Midwest.