Quantification of Nitrogen Lost to Greenhouse Gas Emissions in Cover Crop Systems

View the project final report

Commodities

• Agronomic: corn, wheat

Practices

• Crop Production: cover crops, nutrient cycling

As the cost of inputs increases, farmers seek tools to maintain a competitive edge. One such tool is the use of cover crops, which can improve nitrogen (N) retention in the cropping system and thus decrease the amount of N fertilizer that needs to be applied. Cover crop N release isn’t always in sync with cash crop demand, however. Decomposing fall-planted oilseed radish biomass may release scavenged N too early, while winter-hardy grasses such as annual ryegrass can immobilize N into mid-summer. The former is particularly problematic as it represents N lost from the system; this lost N is both a potential environmental problem and an economic problem. A number of researchers are investigating the amount of N lost to leaching from decomposed oilseed radish biomass. Another, less studied, method by which N may be lost is through greenhouse gas emissions. I propose to quantify the amount of N lost to greenhouse gas emissions when oilseed radish, annual ryegrass, and a mix of the two are planted after wheat harvest in a wheat/corn/soybean rotation. Field corn planting will follow cover crop termination. Data to be collected include cover crop biomass and N content, gas samples taken before/during/after oilseed radish decomposition, soil N content analyses, and corn growth/yield measurements.

Short-term project outcomes include: increased farmer knowledge of cover crops and confidence in their use, and awareness of relationships between cropping systems and greenhouse gas emissions. The intermediate-term outcome is the increased adoption of cover crops, while long-term outcomes are the realizations of benefits accrued due to wide-scale cover crop use.

Short-term outcomes will be measured via use of the Turning Point audience response system, through which surveys will be administered. A farmer panel will also provide input on the project periodically. The intermediate-term outcome will be partially evaluated through the efforts of the MSU Extension cover crop team to quantify changes in cover crop use. Project outcomes have relevance to farmers/ranchers because they will improve the economic and environmental sustainability of producers in the North Central region who use cover crops.

This project will also be evaluated based on its success at outreach. Many of the project outputs serve as outreach methods. Presentations at MSU Ag Expo, the Great Lakes Fruit, Vegetable, and Farm Market Expo (GLEXPO), and winter meetings will reach a wide variety of people. The Midwest Cover Crops Council (MCCC) meeting attracts farmers and researchers with a strong interest specifically in cover crops, as will the planned workshops/field days. The annual meeting Crop Science Society of America attracts primarily researchers; the data from this project will be of interest to both Extension personnel and others investigating the use of cover crops and/or greenhouse gas emissions in agricultural systems.

This project will generate one new MSU Extension bulletin. Data will also be used to update Bulletin E2884 – Cover Crop Choices for Michigan. Brief project update-type articles will also be written for the MSU Extension website. At the regional level, data will be used to update the MCCC online cover crop selector tool. Finally, this project will result in at least one peer-reviewed journal article.