Leonardo M. Bastos, Department of Agronomy, Kansas State University, Manhattan, KS and Charles W. Rice, 2701 Throckmorton Hall, Kansas State University, Manhattan, KS
Global N fertilizer use in agriculture is projected to increase to match the increasing demand for food. Agricultural lands that receive N fertilizer are considered the main source of anthropogenic N2O and account for 68% of total N2O emissions in the US. Strategies that attempt to better match nutrient availability and plant needs, such as N fertilizer source and placement, and the use of enhanced-efficiency fertilizers, are recognized as practices to avoid N losses and increase crop N use efficiency (NUE), but quantification of N2O emissions is needed from these recommended practices. The objective of this study was to evaluate N strategies for N2O emissions. To test for that, treatments consisted of a combination between N source and placement: urea broadcast, UAN broadcast, coated urea broadcast, UAN surface-band, UAN subsurface-band, UAN + nitrification inhibitor subsurface-band and a 0 N control. The N2O emissions were monitored using a steady-state vented chamber, once per week before the fertilizer has been applied, two to three times per week when rainfall events occurred, and once a week otherwise. To date, UAN subsurface-band emitted the most (3.1 kg N-N2O ha-1), whereas the control (0.23 kg N-N2O ha-1), UAN broadcasted (0.52 kg N-N2O ha-1), UAN subsurface-banded + nitrification inhibitor (1.06 kg N-N2O ha-1) and coated-urea broadcasted (1.1 kg N-N2O ha-1) emitted the least. The use of nitrification inhibitor decreased N2O emissions by 66%, when compared to the fertilizer alone.