Simulating the Impact of Climatic Variability on N2O Emissions from a Rain-Fed Wheat-Cropped Soil in a Semi-Arid Climate.

The Water and Nitrogen Management model (WNMM) was applied to simulate N₂O emissions from a rain-fed and wheat-cropped system on a sandy duplex soil at Cunderdin, Western Australia, Australia from May 2005 to May 2007. WNMM satisfactorily simulated crop growth, soil water content and mineral N contents of 0-10 cm topsoil, soil temperatures at depths and N₂O emissions from the soil, compared with the field observations during calibration and validation. About 89% of total N₂O emissions were estimated as nitrification-induced, according to WNMM simulation for this semi-arid and wheat-cropped system. The calibrated and validated WNMM was then deployed to simulate N₂O emissions from this soil from 1970 to 2006 for seven scenarios of N fertiliser application at Cunderdin. This sensitivity test found that the annual N₂O emissions for this rain-fed and wheat-cropped system were significantly correlated to annual average minimum air temperature (r=0.12), annual pan evaporation (r=0.10), N fertiliser application rate (r=0.91) and wheat yield (r=0.35). Based on this 37-year simulation, multivariate regression models for estimating annual N₂O emissions were developed to account for climatic variation (including annual pan evaporation and rainfall) for this rain-fed and wheat-cropped system in Western Australia, which explained over 84% of yearly variations of annual N₂O emissions predicted by WNMM.