Enhanced-efficiency N fertilizers (EENFs) have potential for mitigating N 2O 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 N 2O 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 N 2O emissions by 42% compared with urea and 14% compared with urea-NH 4NO 3 solution (UAN) in no-till and strip-till environments, but had no effect in a conventional tillage environment. A stabilized urea source, SuperU, reduced N 2O emissions by 46% compared with urea and 21% compared with UAN. A stabilized UAN source, UAN+AgrotainPlus, reduced N 2O emissions by 61% compared with urea and 41% compared with UAN alone. A slow-release UAN source, UAN+Nfusion, reduced N 2O emissions by 57% compared with urea and 28% compared with UAN. Urea-NH 4NO 3 reduced N 2O emissions by 35% compared with urea. A linear increase in N 2O emissions with increasing N rate was observed for untreated urea and UAN. Developers of management protocols to reduce N 2O emissions from irrigated cropping systems in semiarid areas can use this information to estimate reductions in N 2O 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.
