Footprints of corn nitrogen management on the following soybean crop

Corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] is among the most typical crop rotations in the U.S. Corn Belt, and N is the most limiting nutrient for both crops. This study aims to assess the effects of N management for corn on the following soybean crop. Two corn-soybean rotation N fertilizer rate studies-a long-term study (1983-2020, Case Study I) and a two-season study (2019-2020, Case Study II)-were conducted in Kansas (United States). Case Study I focused on soybean seed yield as the response variable, whereas Case Study II included a detailed seasonal characterization of soil N, symbiotic N fixation (SNF), and plant N uptake for soybean considering N fertilizer rates on the previous corn crop. Apparent N budgets from corn (N fertilizer minus grain N removal) ranged from approximately -100 to approximately +50 kg N ha(-1), and soybean yields were slightly or not affected by corn N management. Case Study I showed that long-term N budgets in corn crops did not affect the following soybean crop yields. In Case Study II, the previous corn N management produced negative or small N surplus that influenced neither soil residual N nor SNF, without compromising soybean productivity. Farmers applying close to economic optimum N rates on corn will likely not generate scenarios of N surplus to compromise SNF or soybean yields. Forthcoming research should further address how long-term and large soil N mining or surplus in corn may enhance or inhibit N fixation for the next soybean crop.

Automated summary

This study assessed the effects of nitrogen management for corn on the following soybean crop and found that reasonable nitrogen fertilizer application for corn does not negatively impact soybean yields.