Erosion/productivity modelling of maize farming in the Philippine uplands part I: Parameterising the agricultural production systems simulator

This paper describes the parameterisation of the Agricultural Production Systems Simulator (APSIM) model to simulate open-field farming and intercropping of maize with leguminous shrub hedgerows. Whenever possible, parameters for the model were determined from measured or standard values for the environment of the field trials, while other parameters were derived from previous modelling experience in tropical environments. The remaining parameters were derived using step-wise calibration, where one or two parameters were calibrated against closely related measured data. Once parameterised, APSIM gave acceptable predictions of maize yields and soil loss from open-field farming and hedgerow intercropping. The version of APSIM described in this paper is used to simulate maize yields and soil erosion from open-field farming and hedgerow intercropping in the second paper in this series (Nelson et al., this issue). In the third paper, Nelson et al. (this issue) use cost-benefit analysis to compare the economic viability of hedgerow intercropping relative to traditional open-field farming of maize in relatively inaccessible upland areas.