Pedro Vitor Ferrari Machado1, Shannon Brown2, Katelyn Congreves2 and Claudia Wagner-Riddle2, (1)School of Environmental Sciences, University of Guelph, Guelph, ON, CANADA (2)School of Environmental Sciences, University of Guelph, Guelph, ON, Canada
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.