SIMULATION AND EXPERIMENTAL STUDY ON EVAPOTRANSPIRATION OF WHEAT CROP

Abstract

Root water extraction by the plant roots is one of the difficult parameters to estimate, since most of roots lie within the unsaturated zone and the demonstration of the moisture flow within this zone is a complex process. The governing equation is Richard's equation with a sink term representing extraction of water by the root system. Two approaches, a microscopic and a macroscopic methodology, have been developed to simulate water uptake by plant roots. There are different root-water uptake models to determine the extraction rate of soil moisture by roots. All these models differ in the concept, in complexity and in the volume of input data and the parameters needed. Many of these may often show a general agreement with mean measured soil water content of the root zone. However, this doesn't imply that they are satisfactory in predicting the soil water content profiles and that they perform in the same way, because each model is incorporated into a larger more complex soil water simulation model that differs from one to the next in its way of dealing with the other components of the water balance and the imposed upper and lower boundary conditions. Here we have put more emphasis on the microscopic approach and thus we considered a microscopic modelwhich has been developed (by Manoj Kumar Trivedi, 2001, Indian Institute of Technology Roorkee, Roorkee) for the simulation of two dimensional(r-z plane) axis symmetric unsteady state flowin the unsaturated zone towards the plant roots calibrated for the wheat crop. Experimental studies were conducted on the wheat crop to justify the model predicted parameters. The crop growth period was divided into 4 stages in accordance with the model. The observed values of the moisture content show a general agreement with the model predicted values. Keywords: Root water uptake, unsaturatedzone,Plant Transmissivity