Improving the regional nitrogen rate recommendation tool for corn to achieve co-sustainability of crop productivity and ecosystem service

Optimizing nitrogen (N) fertilizer management in corn cultivation requires considering effects on both yield productivity and environmental sustainability. As one of the most important N fertilizer management practices, N rate recommendation in the U.S. Corn Belt has transformed from the yield-based method to the economic returns-based method, which considers the ratio of fertilizer to crop prices in combination with N fertilizer-yield response data (Maximum Return to N, or Maximum Return To N (MRTN)). The MRTN approach generally lowers N rates, thus improving economic return and environmental stewardship; however, environmental loss information (i.e. nitrogen-related loss into the atmosphere, surface, or groundwater) is not directly utilized. Additionally, the impact of environmental conditions (soil and weather conditions) on yield response to fertilizer rate are not explicitly explored and integrated in the recommendation tool. Here, we leveraged both the N trial data collected across Illinois (e.g. N fertilizer-yield responses data), and an advanced agroecosystem model, ecosys, to improve the existing N rate recommendation method in terms of two aspects. (1) We validated ecosys with field trial datasets and added the environmental cost components in the MRTN method by explicitly simulating N leaching and N2O emissions with corresponding environmental costs. (2) By clustering environmental conditions of the Illinois cornfields based on soil (e.g. soil organic carbon) and weather conditions (growing-season temperature and precipitation), we provide spatially explicit N rate recommendations for each clustered region. This study can provide farmers useful guidance on effectively managing N fertilizer in the U.S. Midwest.