228-Optimal Irrigation Schedules Based on Simulated Soil-Moisture Depletion Pattern.

Abstract

Modelling water movement in the cropped soil can give insight into effective management practices to conserve water. Most of the existing root water uptake models solve the equation for moisture flow in the unsaturated soil coupled with a sink term representing moisture uptake by plants. Modelling requires a mathematical description of the process of the uptake of water from the soil profile by the plant root system. In the present study a numerical model, based on a mass conservative, fully implicit finite difference scheme has been formulated, wherein Richards equation coupled with a non-linear root water uptake term has been subject to appropriate boundary conditions. The non linear system of equations is linearized using Picard's iterations and resulting system of equations are solved using Thomas algorithm. The model yields spatial distribution of pressure head and moisture content at successive advancing times in the soil. From the model computed moisture contents, the moisture depletion values at different zones of crop root at different times are computed by numerical integration. The simulated moisture depletions have been compared with field observed data. The field experiments on 'Maize' under controlled conditions have been carried out at Roorkee. The soil moisture variation in the crop root zone has been continuously observed. Comparison of simulated and field observed values indicates high values of statistical parameters, which validates the reliability of the simulation formulated. Hypothetical irrigation schedules based on the simulated root zone soil moisture depletion have been developed to illustrate the applicability of the numerical model.