NUMERICAL MODELLING FOR IRRIGATION SCHEDULING OF CROPS

Abstract

Roots of the agriculture crops mostly lie in the unsaturated zone. The unsaturated zone extends from ground surface to the water table. The soil moisture status in the root zone has an important bearing on the evapotranspiration (ET) of crops. Transpiration defined as the process by which soil moisture is absorbed by the plant roots and evaporated into the atmosphere, is the major component of evapotranspiration in the vegetated areas. While transpiring water, plant roots function like water pumps moving water from the soil and into the atmosphere. The present study involves development of a macroscopic numerical model for simulating one-dimensional vertical unsteady state flow towards the plant root in the unsaturated zone. The model essentially comprises a numerical solution of mixed form of Richard's equation by finite difference method and accounts for the water taken by the plant roots as a sink term. The boundary condition at the root-soil interfabe is assigned more rationally by deriving it from the meteorological conditions prevailing over the plant. A computer program is developed in `CS language to model water flow through unsaturated zone and to plan the irrigation scheduling for wheat crop.