Procedure to estimate ammonia loss after N fertiliser application to moist soil

Decision support systems (DSS) that provide advice on best N fertiliser management practice ideally need to assess the effect that fertiliser type, rate and management have on N loss. Currently only nitrate leaching and denitrification losses can be assessed in Australian DSS that use output from the Agriculture Production Simulator (APSIM). This paper describes a simple spreadsheet-based model for estimating NH3 loss from urea, urea ammonium nitrate and ammonium sulfate that can be used in conjunction or independent of current DSS. The use of scaling factors that reduce NH3 emission on the basis of factors known to be key determinants of NH3 loss, including type of fertiliser used, rate of fertiliser applied, management of fertiliser, rainfall and crop development was found to account for 85% of the variance between predicted and observed values when tested against 40 case studies. The model also had good predictive power with a root mean square error (RMSE) equivalent to 4.8% of N applied.