Enhanced Efficiency Fertilizers: Effect on Nitrous Oxide Emissions in Iowa

Fertilizer application in crop production agriculture is a major factor influencing soil emissions of the greenhouse gas N2O. Enhanced efficiency fertilizers (EEFs) have the potential to decrease N2O emissions by improving the synchrony between soil N supply and crop N demand. This study was conducted to compare the effects of N2O emissions from soil cropped to corn (Zea mays L.) and EEFs and conventional fertilizers. During a 3-yr period, growing-season N2O emissions were quantified in unfertilized check plots and plots fertilized with urea-NH4NO3 (UAN), UAN containing the urease and nitrification stabilizer AgrotainPlus (UAN+Ag), a stabilized urea containing urease and nitrification inhibitors (SuperU), and a controlled-release polymer-coated urea (ESN). In the third year of the study, conventional urea and an additional fertilizer formulation, Nutrisphere, were evaluated. We observed no reductions in cumulative seasonal N2O emissions from treatments fertilized with the EEFs in any of the study years. Generally, N2O emissions were significantly higher than emissions from the check (no fertilizer) treatment. There were no differences among fertilizer types except in 2009 when the ESN treatment had significantly higher emissions than the check, UAN, and UAN+Ag treatments. Our results indicate that, due to the episodic nature of N2O emissions induced by rainfall events, reduction of N2O emissions through the use of EEFs may be limited in rainfed regions.