Impact of Urease and Nitrification Inhibitors, As Well As Nitrogen Application Rate on Nitrogen Losses from Rainfed Spring Wheat Production System.

Urease and nitrification inhibitors have the potential to reduce nitrogen (N) losses and increase N use efficiency from urea fertilized fields. The effectiveness of these inhibitors has been studied extensively in irrigated but not in rainfed systems. Therefore, this study was conducted in 2014 to 2015 growing season to compare the effects of urea (U), stabilized urea with urease and nitrification inhibitor (SU), and stabilized urea with nitrification inhibitor (UI), each applied at two varying rates of 146 and 168 kg N ha-1, on nitrous oxide (N2O) emissions, ammonia (NH3) volatilization, nitrate (NO3-) leaching, as well as on grain yield and protein content of rainfed spring wheat. In 2014, cumulative NH3 volatilization and N2O emissions were significantly reduced by 26 % and 50 % respectively with SU, but no significant reduction was observed with UI compared to U. We did not observe a significant effect of higher N rate on N2O emissions, but lower N application rate (146 kg N ha-1) significantly reduced NH3 volatilization by 26% compared to 168 kg N ha-1. Soil water NO3- concentration below the rooting zone was reduced at lower N application rate and also through the use of SU and UI instead of U. Soil inorganic N intensity was significantly related with cumulative N2O emissions. Nitrogen source and N rate did not influence grain yield and protein content. We concluded that urease and nitrification inhibitors can minimize N losses from rainfed production systems without compromising grain yield and protein content.