Enhanced-Efficiency Nitrogen Fertilizers: Potential Role in Nitrous Oxide Emission Mitigation

Enhanced-efficiency N fertilizers (EENFs) have potential for mitigating N2O emissions from N-fertilized cropping systems. Stabilized EENFs contain nitrification and/or urease inhibitors. Slow-release EENFs contain N components that are slowly released with variable release rates. Controlled-release EENFs release N at more predictable rates. The effectiveness of several EENFs in reducing soil N2O emissions from a clay loam soil under irrigated, corn (Zea mays L.)-based production systems in Colorado (2002-2012) was investigated. A controlled-release, polymer-coated urea, ESN, reduced N2O emissions by 42% compared with urea and 14% compared with urea-NH4NO3 solution (UAN) in no-till and strip-till environments, but had no effect in a conventional tillage environment. A stabilized urea source, SuperU, reduced N2O emissions by 46% compared with urea and 21% compared with UAN. A stabilized UAN source, UAN + AgrotainPlus, reduced N2O emissions by 61% compared with urea and 41% compared with UAN alone. A slow-release UAN source, UAN + Nfusion, reduced N2O emissions by 57% compared with urea and 28% compared with UAN. Urea-NH4NO3 reduced N2O emissions by 35% compared with urea. A linear increase in N2O emissions with increasing N rate was observed for untreated urea and UAN. Developers of management protocols to reduce N2O emissions from irrigated cropping systems in semiarid areas can use this information to estimate reductions in N2O emissions when EENFs are used. Policymakers can use this information to help determine financial credits needed to encourage producers to use these technologies in their crop production systems.