Wheat Cover Crop Management Impacts Corn Yield, Soil Nitrogen Dynamics, and Nitrous Oxide Emission

Agricultural soil  management is the main source of nitrous oxide (N₂O) emission, contributing 78% of total N₂O emissions. Winter cereal cover crops (WCCCs) are recommended as the best in-field management practice to minimize nutrient loss to Illinois water and the Gulf of Mexico. WCCCs including wheat (Triticum aestivum L.) are often terminated 3-4 weeks prior to planting corn. Delaying termination increases nitrogen (N) uptake and decreases N leaching potential. Literature is scant on the effect of wheat termination (early vs. late or cover crop removal) on corn yield and N₂O emission during corn growing season. The objective of the study includes evaluating effect of wheat termination management vs. a no-cover crop control on (I) corn leaf area index (LAI) and grain yield; (II) soil nitrate-N, ammonium-N, and total N dynamics; (III) soil volumetric water content (VWC) and temperature trends; (IV) soil N₂O emission; and (V) yield-scaled N₂O emissions. We found that Corn yield was higher in Fallow and explained by peak LAI values. Majority of N₂O emissions occurred after N fertilization prior to corn V10 growth stage. Soil nitrate-N had its peak period after sidedressing N coinciding with peak N₂O emissions for most of cover crop treatments. Yield-scaled N₂O emission were lowest in the fallow in both years and varies across other cover crop treatments in 2020 and 2021 reflecting on lower N balances in that treatment. Average soil VWC prior to corn V10 growth stage explained 74% of soil N₂O-N emissions indicating when N is supplied in high amount, soil VWC drives N₂O-N emissions. Gram + bacteria was negatively related to cumulative N₂O-N emissions.