Field test of a soil water balance simulation model

A simple soil water balance model is used to simulate the soil water content in the active root zone of mustard crop (Brassica juncea) as well as is tested with field experimental data of 2 years (1998 and 1999) under rain-fed (no irrigation) and irrigated conditions. The model used includes physical process like infiltration from rainfall or irrigation, redistribution in soil water zone, plant water uptake in the form of actual evapotranspiration and percolation out of the soil reservoir. In addition, the model considers dynamics of crop root growth model that affect the plant water uptake and hence the soil water in the unsaturated zone. The model satisfactorily simulates the soil water content in the active root zone of the crop on daily basis. Values of the mean absolute relative error (MARE) index between the observed and simulated soil water content of the rain-fed mustard in 1998 and 1999 are found to be 0.046 and 0.058, respectively, whereas for irrigated mustard, it is 0.051 in 1999. Prediction efficiency (PE) index is found to be 0.98, 0.97 and 0.97 for rain-fed mustard of 1998 and 1999 and irrigated mustard of 1999, respectively. Since the MARE index is low and PE index is high for both rain-fed and irrigated mustard, the model can be used to simulate the soil water content in the active root zone of the crop.