Nitrogen Placement and Source Effects on Nitrous Oxide Emissions and Yields of Irrigated Corn

Limited information is available on how N fertilizer placement affects soil nitrous oxide (N 2 O) emissions under irrigated conditions in the semiarid western United States. Our objective was to compare surface banding near corn row and broadcasting of three N sources (urea, polymer‐coated urea [PCU], and stabilized urea [SU] containing urease and nitrification inhibitors) on N 2 O emissions from a clay loam soil under sprinkler‐irrigated continuous corn production. The N fertilizers were applied at a rate of 202 kg N ha −1 to strip‐till (2010 and 2011) and no‐till (2011) corn at crop emergence, with ∼19 mm irrigation water applied the next day. Band‐applied N had a 1.46‐fold greater N 2 O emission than broadcast N averaged over N sources and three studies. Soil N 2 O–N emissions from urea were 1.48‐ and 1.74‐fold greater than from PCU and SU, respectively, when averaged over N placement and studies. The N placement × source interaction was not significant. Averaged across studies, grain yield and N uptake did not vary with N placement, whereas grain yields were greater for SU than PCU but were not different from urea. Nitrous oxide emissions per unit of N applied, per unit of grain yield, and per unit N uptake were 59, 49, and 47% greater, respectively, with banded than with broadcast N fertilizer. These studies show that N placement and N source selection are important manageable factors that can affect N 2 O emissions and need to be considered when developing N 2 O mitigation practices in irrigated cropping systems in the semiarid western United States.