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

Waterhouse, Hannah, Wade, Jordon, Horwath, William R., Burger, Martin
Journal of environmental quality 2017 v.46 no.5 pp. 1123-1130
Zea mays, ammonia, calcium nitrate, corn, dicyandiamide, furrow irrigation, greenhouse gas emissions, growing season, loam soils, nitrification, nitrification inhibitors, nitrogen, nitrogen fertilizers, nitrous oxide, nutrient use efficiency, stabilizers, starter fertilizers, urea ammonium nitrate, urease, California
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. NH₃), 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.