Simulating response of N 2 O emissions to fertiliser N application and climatic variability from a rain‐fed and wheat‐cropped soil in Western Australia

BACKGROUND: Besides land management and soil properties, nitrous oxide (N 2 O) emissions from the soil may be responsive to climatic variation. In this study the Water and Nitrogen Management Model (WNMM) was calibrated and validated to simulate N 2 O emissions from a rain‐fed and wheat‐cropped system on a sandy duplex soil at Cunderdin, Western Australia, from May 2005 to May 2007, then it was deployed to simulate N 2 O emissions for seven scenarios of fertiliser N application under various climatic conditions (1970–2006). RESULTS: The WNMM satisfactorily simulated crop growth, soil water content and mineral N contents of the surface soil (0–10 cm), soil temperatures at depths and N 2 O emissions from the soil compared with field observations in two fertiliser treatments during calibration and validation. About 70% of total N 2 O emissions were estimated as nitrification‐induced. The scenario analysis indicated that the WNMM‐simulated annual N 2 O emissions for this rain‐fed and wheat‐cropped system were significantly correlated with annual average minimum air temperature ( r = 0.21), annual pan evaporation ( r = 0.20) and fertiliser N application rate ( r = 0.80). Both annual rainfall and wheat yield had weak and negative correlations with annual N 2 O emissions. Multiple linear regression models for estimating annual N 2 O emissions were developed to account for the impacts of climatic variation (including temperature and rainfall), fertiliser N application and crop yield for this rain‐fed and wheat‐cropped system in Western Australia, which explained 64–74% of yearly variations of the WNMM‐estimated annual N 2 O emissions. CONCLUSION: The WNMM was tested and capable of simulating N 2 O emissions from the rain‐fed and wheat‐cropped system. The inclusion of climatic variables as predictors in multiple linear regression models improved their accuracy in predicting inter‐annual N 2 O emissions. Copyright © 2011 Society of Chemical Industry