Erosion/productivity modelling of maize farming in the Philippine uplands; part 1: a simple description of the agricultural production systems simulator
1996
Nelson, R.A. | Dimes, J.P. | Silburn, D.M. | Carberry, P.S.
Erosion/productivity models summarize and mathematically represent erosion and crop growth processes, and provide a fast and inexpensive way of exploring the long term consequences of different farming methods. This paper provides an overview of the processes simulated within the Agricultural Production Systems Simulator (APSIM) to improve the relevance and accessibility of the model to those unfamiliar with cropping systems models. APSIM is a point-scale cropping systems model simulating soil physical and crop growth processes on a daily time step. A feature of APSIM is that the soil, rather than the crop, forms the central unit on which all the processes described in the model operate. The water content of each soil layer is calculated from daily infiltration, drainage, unsaturated flow, soil evaporation and transpiration. Soil carbon dynamics are simulated through the decomposition of organic carbon on the soil surface and within the soil profile. Mineral nitrogen available to plant uptake is simulated through various transformations of carbon; losses such as leaching, denitrification and erosion; and additions from inorganic fertilizers and surface residues. The phenology and growth of maize are simulated from daily temperature, radiation and growth stress factors for soil water and nitrogen. Erosion is calculated from slope gradient, runoff and surface cover, and reduces soil depth, waterholding capacity, nitrogen and carbon. APSIM can be used to simulate the key agronomic features of hedgerow intercropping, by parameterising the runoff and erosion modules to predict measured runoff and erosion from fields with hedgerows. The effect of adding hedgerow prunings can be simulated by adding legume biomass from outside the plant/soil system. Maize yields predicted by APSIM can be adjusted for the effects of hedgerow/crop competition using measured yield depression for different soil conditions
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