Plot-level soil fertility & crop productivity

Following equations proposed by Trenbath (1984, 1989), soil fertility (operationally defined as ‘the ability of a soil to support crop growth’) is assumed to proportionally decline during cropping periods and improve during fallow periods, with a characteristic half time of recovery. Fertilizer application may affect soil fertility through reductions on the depletion rate. Current soil fertility of cultivated plots is translated into crop productivity through a conversion efficiency of the crop. Crop sensitivity to stochastic weather and pressure of pest and diseases is also taken into account, with user-defined ranges for these impacts. Part of the landscape can be initialized as ‘wetland’, allowing for paddy rice cultivation with different yield trajectories and soil fertility dynamics than occur in the ‘upland’ plots.