Nitrogen Source Effects on Soil Nitrous Oxide Emissions from Strip-Till Corn

Nitrogen (N) application to crops generally results in increased nitrous oxide (N2O) emissions. Commercially available, enhanced-efficiency 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 strip-till (ST) corn (Zea mays L.) production system. Enhanced-efficiency N fertilizers evaluated were a controlled-release, polymer-coated urea (ESN), stabilized urea, and UAN products containing nitrification and urease inhibitors (SuperU and UAN+AgrotainPlus), and UAN containing a slow-release N source (Nfusion). Each N source was surface-band applied (202 kg N ha(-1)) at corn emergence and watered into the soil the next day. A subsurface-band ESN treatment was included. Nitrous oxide fluxes were measured during two growing seasons using static, vented chambers and a gas chromatograph analyzer. All N sources had significantly lower growing season N2O emissions than granular urea, with UAN+AgrotainPlus and UAN+Nfusion having lower emissions than UAN. Similar trends were observed when expressing N2O emissions on a grain yield and N uptake basis. Loss of N2O-N per kilogram of N applied was < 0.8% for all N sources. Corn grain yields were not different among N sources but greater than treatments with no N applied. Selection of N fertilizer source can be a mitigation practice for reducing N2O emissions in strip-till, irrigated corn in semiarid areas.