Nitrogen Credits and Fertilizer Dollars Saved: Identifying benefits for seeding diverse legume-based cover mixes into or after winter small grains

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Commodities

• Agronomic: clovers, corn, rye, wheat

Practices

• Crop Production: cover crops, cropping systems, crop rotation, nutrient cycling, nutrient management
• Education and Training: demonstration, on-farm/ranch research

Among grain growers in the Midwest, interest is growing in cultivating winter small grains followed by a legume cover crop to take advantage of the growing window after small grain harvest in July. By eliminating this late summer fallow, the soil is protected by maintaining plant cover and farmers can take advantage of nitrogen (N) fixation to benefit the following crop in rotation while contributing to soil health by keeping living roots in the soil and feeding microbes. Growers assume the legume cover is providing an N credit to the following corn crop, although research-backed estimates for these credits are not widely available and have mostly focused exclusively on red clover. We have convened a network of growers using more diverse legume mixes after winter grains who need good estimates of N credits to reduce their fertilizer inputs and costs. This project convenes growers, a nonprofit-based agroecologist, and a UW Extension Educator to identify cover biomass N, soil health benefits, N credits to the following corn crop (via an N fertilizer yield response experiment) and fertilizer dollar value for six different cover crop mixes on 6 farms. Results will be published in case studies, factsheets, and presented at grower conferences.

1. Quantify biomass production, N fixation, and soil health benefits of several legume-based cover mixes by collecting data on 6 collaborating farms and describe via 3 case studies.
2. Identify N credits of legume-based mixes to the following corn crops by measuring corn yield in N fertilizer response field trials on each collaborating farm.
3. Develop Extension factsheet reporting legume biomass, N credit values, and corresponding fertilizer $ values, among legume-based cover crop treatments, to aid grower decision making.
4. Present results and disseminate published products alongside collaborating growers at 2 on-farm field days and at 3 annual grower conferences.