Title: LRBF meshless methods for predicting soil moisture distribution in root zone

Abstract: In this paper, we first propose a coupled numerical model of unsaturated flow in soils and plant root water uptake. The Richards equation and different formulations are used in the developed numerical model to describe infiltration in root zone and to investigate the impact of the plant root on the distribution of soil moisture. The Kirchhoff transformed Richards equation is used and the Gardner model is considered for capillary pressure. In our approach, we employ a meshless method based on localized radial basis functions (LRBF) to solve the resulting system of equations. The LRBF approach is an accurate and computationally efficient method that does not require mesh generation and is flexible in addressing high-dimensional problems with complex geometries. Furthermore, this method leads to a sparse matrix system, which avoids ill-conditioning issues. We implement the coupled numerical model of infiltration and plant root water uptake for one, two, and three-dimensional soils. Numerical experiments are performed using nontrivial analytical solutions and available experimental data to validate the coupled numerical model. The numerical results demonstrate the performance and ability of the proposed numerical method to predict soil moisture dynamics in root zone.