Effects of Positively Charged Dicyandiamide and Nitrogen Fertilizer Sources on Nitrous Oxide Emissions in Irrigated Corn

Synthetic nitrogen (N) fertilizer formulations vary in their effects as substrates on nitrous oxide (N2O) emissions. Mitigation of N2O emissions can potentially be achieved through appropriate choice of N fertilizer sources combined with stabilizers. The effects of three N fertilizers and urease and nitrification inhibitors on N2O emissions, crop N uptake, and yields were determined in a furrow-irrigated corn (Zea mays L.) system in Reiff loam soil in the Sacramento Valley of California for one growing season. Aqua ammonia (Aq. NH 3), urea ammonium nitrate (UAN), and calcium nitrate were sidedressed at the rate of 202 kg N ha(-1). The control treatment received only starter fertilizer (20 kg N ha(-1)). Total seasonal emissions were in the order Aq. NH3 > UAN > calcium nitrate = control with 1.38, 0.97, 0.35, and 0.27 kg N2O-N ha(-1), respectively. A novel, positively charged form of dicyandiamide, KAS-771G77 (G77), was combined with Aq. NH3 and UAN to test the effectiveness of this nitrification inhibitor in reducing N2O emissions. When combined with Aq. NH3, G77 did not reduce the emissions, but G77 significantly lowered them in the UAN treatment. A similar reduction of N2O emissions in the UAN treatment was achieved with the urease and nitrification inhibitor AgrotainPlus. Yields and N use efficiency did not differ among the fertilized treatments. Ammoniacal fertilizers had higher N2O emissions than nitrate-based fertilizers, which could imply nitrification pathways as a source of N2O emissions. The use of G77 or AgrotainPlus, when applied with UAN, was an effective N2O mitigation practice.