Simulation of the Water Dynamics and Root Water Uptake of Winter Wheat in Irrigation at Different Soil Depths

Abstract

Soil water content (SWC) distribution plays an important role in root water uptake (RWU) and crop yield. Reasonable deep irrigation can increase the yield of winter wheat. The soil water movement model of winter wheat was established by considering the root water uptake and the different soil depths of irrigation and using the source term of the soil water movement equation to simulate irrigation at different soil depths. For model verification, experiments on three treatments of winter wheat growth were conducted at irrigation soil depths of 0% (T1), 40% (T2), and 70% (T3) of the distribution depth of the winter wheat root system. The SWC calculated by the model is in accordance with the dynamic change trend of the measured SWC. The maximum absolute error of the model was 0.022 cm3/cm3. The maximum average relative error was 7.95%. The maximum root mean square error was 0.28 cm3/cm3. Therefore, the model has a high simulation accuracy and can be used to simulate the distribution and dynamic changes of SWC of winter wheat in irrigation at different soil depths. The experimental data showed that irrigation soil depth has a significant effect on the root distribution of winter wheat (p < 0.05), and deep irrigation can reduce the root length density (RLD) in the upper soil layers and increase the RLD in the deeper soil layers. The dynamic simulation of RWU and SWC showed that deep irrigation can increase the SWC and RWU in deep soil and decrease the SWC and RWU in upper soil. Consequently, deep irrigation can increase the transpiration of winter wheat, reduce evaporation and evapotranspiration, and increase the yield of winter wheat.