Nitrous Oxide Emissions from a Corn Field in Response to Adopting Best Management Practices for Nitrogen Fertilization.

Nitrous oxide (N₂O) emissions are a global concern because N₂O is a potent greenhouse gas and also contributes to ozone destruction. Agricultural soils + nitrogen (N) fertilizers contribute to global N₂O emissions. Synchronizing N fertilization with plant N demand contributes to mitigating agricultural N₂O emissions. Applying N at the right time and using improved N sources, such as fertilizers treated with urease and nitrification inhibitors are ways of achieving this synchronicity. Despite the potential of urease and nitrification inhibitors to mitigate N₂O emissions, results from the literature are not consistent. The aim of this study was to compare N₂O emission from a corn (Zea mays L.) field in response to four combinations of N fertilization management practices, consisting of (1) urea fertilizer applied at planting (conventional practice) (2) applying urea treated with urease and nitrification inhibitor at planting instead of conventional urea, (3) delaying N fertilization from planting to side-dress stage (UAN application), and (4) combining the use of UAN treated with inhibitors and delayed application. Half hourly N₂O fluxes were measured semi-continuously by a micrometeorological method for each of the four management practices. Preliminary results from 2015 showed no difference in daily N₂O flux between urea and urea treated with inhibitors applied at planting (p>0.05). Also, no difference in N₂O flux was found between the conventional practice and the plot side-dress fertilized with UAN (p>0.05). Notably, the combination of both improved N source and better timing of N fertilization resulted in lower N₂O emission compared to UAN applied at side-dress stage, and compared to urea applied at planting (p<0.05). These results clarify some of the questions associated with adoption of  best management practices in mitigating N₂O emission. This trial will be continued into 2016 to test interannual variability effects on N₂O emission.