Soil water balance and plant water stress

Abstract

The soil water balance is calculated in the DSSAT crop models in order to evaluate the possible yield reduction caused by soil and plant water deficits. The model evaluates the soil water balance of a crop or fallow land on a daily basis as a function of precipitation, irrigation, transpiration, soil evaporation, runoff and drainage from the profile. The soil water is distributed in several layers with depth increments specified by the user. Water content in any soil layer can decrease by soil evaporation, root absorption, or flow to an adjacent layer. The limits to which water can increase or decrease are input for each soil layer as the saturated upper limit. The values used for these limits must be appropriate to the soil in the field, and accurate values are quite important in situations where the water input supply is marginal.