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Combining Urease and Nitrification Inhibitors with Incorporation Reduces Ammonia and Nitrous Oxide Emissions and Increases Corn Yields

Drury, Craig F., Yang, Xueming, Reynolds, W. Dan, Calder, Wayne, Oloya, Tom O., Woodley, Alex L.
Journal of environmental quality 2017 v.46 no.5 pp. 939-949
Zea mays, ammonia, application methods, corn, grain yield, greenhouse gas emissions, nitrification inhibitors, nitrogen, nitrogen fertilizers, nitrous oxide, pollution, soil degradation, urea, urea ammonium nitrate, urease, urease inhibitors, volatilization, weather
Less than 50% of applied nitrogen (N) fertilizer is typically recovered by corn (Zea mays L.) due to climatic constraints, soil degradation, overapplication, and losses to air and water. Two application methods, two N sources, and two inhibitors were evaluated to reduce N losses and enhance crop uptake. The treatments included broadcast urea (BrUrea), BrUrea with a urease inhibitor (BrUrea+UI), BrUrea with a urease and a nitrification inhibitor (BrUrea+UI+NI), injection of urea ammonium nitrate (InjUAN), and injected with one or both inhibitors (InjUAN+UI, InjUAN+UI+NI), and a control. The BrUrea treatment lost 50% (64.4 kg N ha⁻¹) of the applied N due to ammonia volatilization, but losses were reduced by 64% with BrUrea+UI+NI (23.0 kg N ha⁻¹) and by 60% with InjUAN (26.1 kg N ha⁻¹). Ammonia losses were lower and crop yields were greater in 2014 than 2013 as a result of the more favorable weather when N was applied in 2014. When ammonia volatilization was reduced by adding a urease inhibitor, N₂O emissions were increased by 30 to 31% with BrUrea+UI and InjUAN+UI compared with BrUrea and InjUAN, respectively. Pollution swapping was avoided when both inhibitors were used (BrUrea+UI+NI, InjUAN+UI+NI) as both ammonia volatilization and N₂O emissions were reduced, and corn grain yields increased by 5% with BrUrea+UI+NI and by 7% with InjUAN+UI+NI compared with BrUrea and InjUAN, respectively. The combination of two N management strategies (InjUAN+UI+NI) increased yields by 19% (12.9 t ha⁻¹) compared with BrUrea (10.8 t ha⁻¹).