Nitrogen Source and Placement Effects on Soil Nitrous Oxide Emissions from No‐Till Corn

A nitrogen (N) source comparison study was conducted to further evaluate the effects of inorganic N source and placement on growing‐season and non‐crop period soil nitrous oxide (N2O). Commercially available controlled‐release N fertilizers were evaluated for their potential to reduce N2O emissions from a clay loam soil compared with conventionally used granular urea and urea‐ammonium nitrate (UAN) fertilizers in an irrigated no‐till (NT) corn (Zea maysL.) production system. Controlled‐release N fertilizers evaluated were: a polymer‐coated urea (ESN), stabilized urea (SuperU), and UAN+AgrotainPlus (SuperU and AgrotainPlus contain nitrification and urease inhibitors). Each N source was surface band applied (202 kg N ha−1) near the corn row at emergence and watered into the soil the next day. Subsurface banded ESN (ESNssb) and check (no N applied) treatments were included. Nitrous oxide fluxes were measured during two growing seasons and after harvest using static, vented chambers. All N sources had significantly lower growing‐season N2O emissions than granular urea (0.7% of applied N), with UAN+AgrotainPlus (0.2% of applied N) and ESN (0.3% of applied N) having lower emissions than UAN (0.4% of applied N). Similar trends were observed when expressing N2O emissions on a grain yield and N uptake basis. Corn grain yields were not different among N sources but were greater than the check. Selection of N fertilizer source can be a mitigation practice for reducing N2O emissions in NT, irrigated corn in semiarid areas. In our study, UAN+AgrotainPlus consistently had the lowest level of N2O emissions with no yield loss.