Simulating response of N2O 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 (N2O) 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 N2O 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 N2O emissions for seven scenarios of fertiliser N application under various climatic conditions (19702006). 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 N2O emissions from the soil compared with field observations in two fertiliser treatments during calibration and validation. About 70% of total N2O emissions were estimated as nitrification-induced. The scenario analysis indicated that the WNMM-simulated annual N2O 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 N2O emissions. Multiple linear regression models for estimating annual N2O 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 inWestern Australia, which explained 64-74% of yearly variations of theWNMM-estimated annual N2O emissions. CONCLUSION: The WNMM was tested and capable of simulating N2O 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 N2O emissions. (C) 2011 Society of Chemical Industry