Corn Nitrogen Management Influences Nitrous Oxide Emissions in Drained and Undrained Soils

To date, no studies have evaluated nitrous oxide (N₂O) emissions of a single versus a split-nitrogen (N) fertilizer application under different soil drainage conditions for corn (Zea mays L.). The objective of this study was to quantify season-long cumulative N₂O emissions, N use efficiency, and soil N dynamics when corn received a recommended N rate as single or split-N application in Minnesota soils with and without tile drainage over two growing seasons. Preplant urea was broadcast incorporated, and in-season split-N was broadcast as urea plus urease inhibitor. Tile drainage reduced N₂O emissions during periods of excess moisture but did not affect grain yield or other agronomic parameters. Conversely, when precipitation was adequate and well distributed, tile drainage did not affect N₂O emissions, but it did enhance grain yield. Averaged across years, the undrained soil emitted 1.8 times more N₂O than the drained soil (2.36 vs. 1.29 kg N ha^-1). Compared with the Zero-N control, the Single Preplant and Split N applications emitted 2.1 and 1.6 times more N₂O, produced 1.4 and 1.3 times greater grain yield, and resulted in 1.5 and 1.4 times more residual soil total inorganic N, respectively. Per unit of grain yield, the Split application emitted similar amounts of N₂O as the Zero-N control. Averaged across years and drainage, the Split application emitted 26% less N₂O than the Single Preplant application (1.84 vs. 2.48 kg N ha^-1; P² < 0.001) with no grain yield differences. These results highlight that soil drainage can reduce N₂O emissions and that a split N application may be a feasible way to achieve N₂O reduction while enhancing grain yield.