lntercropping the Perennial Grain Kernza® with Legumes for Sustained Economics and Environmental Benefits

View the project final report

Commodities

• Agronomic: grass (misc. perennial)

Practices

• Crop Production: cropping systems, fertilizers, intercropping, nutrient cycling, organic fertilizers
• Education and Training: farmer to farmer, networking, on-farm/ranch research, participatory research
• Farm Business Management: new enterprise development
• Natural Resources/Environment: biodiversity, carbon sequestration, soil stabilization
• Pest Management: competition
• Production Systems: agroecosystems, organic agriculture
• Soil Management: nutrient mineralization

Kernza^® (grain harvested from intermediate wheatgrass; Thinopyrum intermedium) is becoming the country’s first widely available perennial grain crop, which has potential to be a profitable alternative crop that greatly decreases the environmental impacts associated with US agriculture. The ecological sustainability of Kernza could be further improved using legume intercropping practices to reduce or eliminate synthetic nitrogen fertilizer requirements and improve soil health. Problems being addressed include a) limited agronomic advice for managing legume/Kernza intercrops to optimize profitability and ecological services regionally, b) a lack of quantifiable soil health metrics resulting from legume/Kernza intercrops and c) insufficient support for farmers to develop and share information and experiences related to Kernza production. This project identified solutions to these problems by conducting research trials on farm and at research institutions to develop agronomic recommendations for managing legume/Kernza intercrops, to quantify the soil health impacts from legume/Kernza intercrops, and to develop and support a Kernza Growers Network for farmers to engage and share knowledge with other farmers and researchers related to Kernza production. Results from our institutional research studies show that legume establishment and productivity varied by species and location. As expected, Sainfoin performed well in KS by producing biomass and not reducing Kernza grain yields more than other legume treatments compared to fertilized monocultures. Alfalfa was also a strong intercrop legume producing well under drought conditions. Slight reductions in Kernza grain yields were measured in all Kansas legume treatments in the establishment year, but no reductions were measured in year two. Sainfoin was not a good legume for the northern environments as biomass was very low. Alfalfa performed well as an intercrop in Minnesota as it resulted in positive N mineralization in year 2, produced consistent biomass yields, and supported Kernza grain yields equal to fertilized monocultures. Alfalfa also dominated in the mixture with red clover and white clover in Minnesota. Legume intercropping with Kernza resulted in similar Kernza grain yields compared to fertilized monocultures in Wisconsin in year one, but yields were lower in year two. There was no effect of legume intercropping on soil aggregate stability in the timeframe of this project. On-farm trials were successfully established and grain yields in the intercropped treatments were similar to monoculture controls in Minnesota. Unlike previous studies, Kernza grain yields did not decline in the third year of production. By the third year, total straw biomass (Kernza plus legume biomass) was greater in the intercropped plots compared to the monoculture in Minnesota. Results from this study were shared broadly at various events, all of which were designed to strengthen the network of Kernza growers and facilitate knowledge transfer from experienced growers to new and future growers. Since starting this project, on-farm partners have become more involved in growing and marketing Kernza and have helped this new crop expand on the landscape and in the marketplace.

Agronomic knowledge of legume-Kernza intercropping systems to improve Kernza yields while reducing costly nitrogen fertilizer inputs. We determined which legumes work well as intercrops in three states and develop recommendations for managing legumes with Kernza. Ecological knowledge quantified soil health impacts of legume intercrops, including changes in nitrogen mineralization. Outreach activities improved grower connectedness and provided education, management documents, field days, and winter workshops. Skills and awareness for farmers to successfully produce profitable Kernza yields without expensive synthetic fertilizers.