Modeling soil water movement with water uptake by roots

Soil water movement with root water uptake is a key process for plant growt h and transport of water and chemicals in the soil-plant system. In this st udy, a root water extraction model was developed to incorporate the effect of soil water deficit and plant root distributions on plant transpiration o f annual crops. For several annual crops, normalized root density distribut ion functions were established to characterize the relative distributions o f root density at different growth stages. The ratio of actual to potential cumulative transpiration was used to determine plant leaf area index under water stress from measurements of plant leaf area index at optimal soil wa ter condition. The root water uptake model was implemented in a numerical m odel. The numerical model was applied to simulate soil water movement with root water uptake and simulation results were compared with field experimen tal data. The simulated soil matric potential, soil water content and cumul ative evapotranspiration had reasonable agreement with the measured data. P otentially the numerical model implemented with the root water extraction m odel is a useful tool to study various problems related to flow transport w ith plant water uptake in variably saturated soils.