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Irrigation and N fertilizer management are important factors affecting crop yield, N fertilizer recovery efficiency, and N losses as nitrous oxide (N 2 O) and nitrate (NO 3 −) . Split application of conventional urea (split‐U) and/or one‐time application of products designed to perform as enhanced‐efficiency N fertilizers may mitigate N losses. The objective of this study was to compare the effects of controlled‐release polymer‐coated urea (PCU), stabilized urea with urease and nitrification inhibitors (IU) and split‐U on direct soil‐to‐atmosphere N 2 O emissions, NO 3 − leaching, and yield for fully irrigated and minimum‐irrigated corn in loamy sand. Indirect N 2 O emissions due to NO 3 − leaching were estimated using published emission factors (EF 5 ). Split‐U increased yield and N uptake compared with preplant‐applied PCU or IU and decreased NO 3 − leaching compared with PCU. Direct N 2 O emissions were significantly less with IU or split‐U than with PCU, and there was a trend for greater emissions with split‐U than with IU ( P = 0.08). Irrigation significantly increased NO 3 − leaching during the growing season but had no significant effect on direct N 2 O emissions. After accounting for significantly increased yields with irrigation, however, N losses expressed on a yield basis did not differ and in some cases decreased with irrigation. Post‐harvest soil N and soil‐water NO 3 − in spring showed the potential for greater N leaching in minimum‐irrigated than fully irrigated plots. Indirect emissions due to NO 3 − leaching were estimated to be 79 to 117% of direct emissions using the default value of EF 5 , thus signifying the potential importance of indirect emissions in evaluating management effects on N 2 O emissions.
Maharjan et al. (Fri,) studied this question.