Simulating nitrogen loss due to ammonia volatilisation after urea fertiliser application in APSIM

Abstract

Excess nitrogen (N) use in agriculture has greatly disturbed N cycling exceeding its planetary boundary with serious sustainability implications. Systems modelling allows the integration of interactions between daily moisture, energy and processes of N cycling to better understand N dynamics in diverse farming systems to improve N use efficiency. However, the most widely used agricultural systems model in Australia, the Agricultural Production Systems sIMulator (APSIM), only assesses nitrate leaching and denitrification losses. Ammonia volatilisation is a key pathway for N loss in agricultural systems. This study implemented two methods to estimate likely N loss due to ammonia volatilisation after urea application in APSIM Next Generation and assessed their reliabilities in dryland cereal cropping and pasture systems using published datasets from diverse locations in Australia. The methods allowed the prediction of N volatilised from topsoil N pools iusing easy-to-obtain parameters based on whether the field is cropped, in fallow or under pasture, and whether detailed climate data (e.g. wind speed) is available. Cross validation showed that the methods have moderate predictive accuracy at a daily time step compatible with the certainty of the model inputs and the scale of model application, allowing flexibility for users to choose the appropriate method based on data availability. The inclusion of ammonia volatilisation pathway is useful for the realistic representation and analysis of N dynamics to enable effective N fertilisation to achieve sustainable outcomes.

Yunru (Chloe) Lai

Research Fellow - Soil and Crop Modelling

My research interests include pedometrics, empirical and mechanistic soil and crop modelling.