Nitrogen Source Effects On Nitrous Oxide Emissions From An Irrigated No-Till Corn Field (GRACEnet).

The effect of several N sources on nitrous oxide (N₂O) emissions from an irrigated, no-till (NT) continuous corn field was investigated.  Emissions were monitored in plots receiving 246 kg N/ha during the 2007 growing season and 202 kg N/ha during the 2008 growing season.  Nitrogen sources included dry granular urea, liquid urea-ammonium nitrate (UAN), two polymer-coated urea (PCU) sources, and urea and UAN treated with nitrification and urease inhibitors.  The N was surface band applied in the corn row at emergence with 1.3 cm of irrigation water applied within 3 days of N application.  Plot size was 2.7 x 4.6 m for each N source, with 3 replications in a randomized complete block design.   N₂O fluxes were measured during the growing season at two locations within each plot using static, vented chambers, one to three times per week, and a gas chromatograph analyzer.  In 2007, N₂O emissions were not significantly different between urea and UAN.   The PCU fertilizers and urea and UAN fertilizers treated with nitrification and urease inhibitors showed significantly lower N₂O emissions than dry granular urea in 2007.  Only the urea and UAN sources treated with the nitrification inhibitors had significantly lower N₂O emissions than UAN in 2007.  Based on the 2007 results, these N sources need further evaluation to determine their effectiveness in reducing N₂O emissions in irrigated cropping systems.  The study was continued in 2008.