Assessing the impacts of different nitrogen application strategies on corn productivity and environmental sustainability in Illinois

Improving nitrogen (N) fertilizer management strategies is urgently needed to meet the economic and environmental objectives in increasing nitrogen use efficiency (NUE) for agroecosystems. To evaluate impacts of different N application strategies on crop productivity and environmental sustainability in the U.S. Midwestern agroecosystem, we quantified crop yield and N losses (i.e. N leaching and N2O emissions) at seven continuous corn fields in Illinois with different N application strategies using an advanced process-based model, ecosys, after a comprehensive validation of the model performance. Specifically, we first did simulations for 12 different fertilizer application strategies at each field, including fall applications with or without nitrification inhibitors, spring application, and 9 side-dress applications. For the side-dress applications, we applied part of the total N fertilizer at planting (25%, 50%, and 75%), and applied the remaining fertilizer to the field at different growth stages ranging from V1 to V18 stages. We then conducted both economic assessments and cradle-to-farm-gate life cycle assessment (LCA) to evaluate how these different application strategies perform in terms of total economic benefits and carbon intensity (CI). We found that (1) applying fertilizer in fall had the lowest NUE and caused the largest yield loss compared with spring applications, which can be mitigated but cannot be eliminated by adding nitrification inhibitors and/or more N fertilizer. (2) Side-dress at earlier growth stages (V1-V6) with higher side-dress-to-total proportion (75%) can reduce N loss and increase cron grain yield to the greatest extent compared with spring applications, and add more fertilizer can improve the benefits of earlier side-dress on reducing N loss and increasing crop yield. (3) Earlier side-dress had higher total economic benefits especially at higher ratio of fertilizer to crop prices, and had lower CI mainly due to less CO2 emissions among all fertilizer application strategies. Our findings provide useful insights to improve N fertilizer management in the U.S. Midwestern agroecosystems.