Soil Moisture Dynamics Modeling Considering the Root Compensation Mechanism for Water Uptake by Plants

摘要

A numerical model is developed in this study for simulating soil moisture flow in layered soil profile with plant growth. A dynamic root compensation mechanism (RCM) is used for a nonuniform root distribution pattern to compute water uptake by plants in a moisture scarce environment. The governing soil moisture flow equation integrated with the roots water uptake function is solved numerically by the implicit finite difference method coupled with the Picard iteration technique. The model is first tested for a barren layered soil profile using numerical simulation data available in the literature. A nonlinear function for water uptake by roots is then incorporated in the flow equation and the rate of water removal is simulated with and without considering the RCM for a characteristic example under optimal and water scare conditions. The model is finally applied to a rain-fed wheat (Triticum aestivum) field using a dynamic root growth model. The simulation considering the RCM shows better agreement with the observed data compared to the model results obtained without considering the RCM. Results show that under favorable soil moisture conditions, plants extract water at the maximum rate according to the root distribution pattern and when the moisture stress is developed in the upper soil profile, the diminished water uptake rate in the water scarce region is compensated for by an enhanced water uptake from the lower wetter layers. The model can be used for sound irrigation management practices especially in the water scarce arid and semiarid regions and can also be integrated with a transport equation to predict the solute uptake by plant root biomass.