N Fertilizer Management Impacts N2O Emissions and Grain Yield in No-till Corn.

Agricultural lands that receive N inputs are considered primary source of N₂O, a potent greenhouse gas. The objective of this study was to assess the impact of N source and placement on N₂O emissions and corn grain yield. The experiment was conducted at the Agronomy North Farm located at Kansas State University, Manhattan, KS. The soil was a moderately well-drained Kennebec silt loam. The treatments were broadcast urea (BC-Urea), broadcast urea ammonium nitrate (UAN) (BC-UAN), broadcast coated urea (BC-CU), surface-band UAN (SB-UAN), subsurface-band UAN (SSB-UAN), subsurface-band UAN + nitrification inhibitor (SSB-UAN+I) and a 0 N control. Treatments were arranged on a randomized complete block design with four replicates. The N₂O emissions were monitored during the 2013 and 2014 growing seasons using static non-steady state vented chambers. In 2013, SSB-UAN emitted significantly more N₂O (2.4 kg N-N₂O ha^-1), whereas the control (0.3 kg ha^-1) and BC-UAN (0.6 kg ha^-1) treatments emitted the least. In 2014, most treatments emitted 3.3 to 2.5 kg N-N₂O ha^-1. Only SSB-UAN+I (0.97 kg ha^-1) and the control (0.26 kg ha^-1) were statistically significantly lower. The use of nitrification inhibitor decreased N₂O emissions by 62% and 55% in 2013 and 2014, respectively. In 2013, the highest grain yields were obtained under SSB-UAN (10.5 Mg ha^-1) and SB-UAN (9.8 Mg ha^-1). Accounting for both total N₂O emitted and grain yield, SB-UAN resulted in the best performance in 2013. Fertilizer source and placement management have the potential to both mitigate N₂O emissions and promote high yields in corn.