The Influence of Winter Cover Crops on Nitrous Oxide (N2O) Emissions from Midwest Row-Crops.

The practice of including winter cover crops in Midwest row-crop systems is increasing. This perennializaton of annual crop systems can provide climate stabilization through additional soil carbon storage, and perhaps nitrous oxide (N₂O) mitigation.

Nitrous oxide is the largest contributor to the greenhouse gas (GHG) burden of cropping systems in the US. An increase or decrease in emissions of N₂O from the soil due to management change, such as cover crop planting, can make the difference between abating or raising the overall Global Warming Impact (GWI) of the system. Limited, longer-term N₂O emissions data from winter cover crops make this evaluation challenging.

Here, we will present twelve site years of N₂O emissions data from a corn-soybean rotation, either with or without cover crops (grass – legume mixture) under conventional management, at the Kellogg Biological Station in SW Michigan.

Results show that including cover crops in annual crop systems did not have much affect on total N₂O emissions compared to their absence. There was evidence for decreased emissions in soybean years following cover crops, but not in corn years following cover crops. N₂O emissions were highest in corn (vs. soybean) years, irrespective of cover crop presence or absence. The largest N₂O fluxes occurred following fertilization, soil disturbance (annual crop planting and cover crop termination), and rainfall.