Simulating water uptake in the root zone with a microscopic-scale model of root extraction

Abstract

Root water uptake is a key element for analysing the evolution of soil water content, which regulates crop transpiration. Our objective was to design a model taking into account the vertical water redistribution and the root water uptake in order to assess the regulation of plant transpiration induced by the effective soil water availability. To do so, the root water uptake is described with a microscopic-scale model integrated within a classical model of vertical water redistribution. For root water uptake, the root water potential, leading the water transfer from soil to roots, is calculated in order to satisfy the climatic demand... By coupling the microscopic and macroscopic approaches to soil water transfer, the regulation of transpiration can be directly linked to soil hydraulic properties and to effective soil water availability: the numerical model is applied to simulate soil water movement with root water uptake, and simulation results are compared with a series of findings on plant functioning obtained by previous work. Qualitatively, simulated transpiration in response to the soil water content is reasonably consistent with the description of crop behaviour in drying soils and in soil with vertical water heterogeneity. The results are also compared with experimental results in order to evaluate the usefulness of this model: with conventional measurements under field conditions, the prediction of water balance evolution is rather consistent with experimental results.