ESTIMATION OF NON–LINEAR ROOT WATER UPTAKE PARAMETER FOR WHEAT CROP

Abstract

The root water uptake is an important factor in controlling the yield of crops. Irrigation is applied in order to ensure the availability of water for plants through system of roots. The rising scarcity of water demands for optimization of irrigation. This irrigation optimization is characterised by root water uptake by plant roots which depends on soil moisture content, transpiration, root depth & growing period of crops. Many root water uptake models of varying nature (like linear models, non-linear models, constant models exponential models etc.) were introduced for finding the moisture extracted from the root zone. However non-linear root water uptake models give more accurate results in comparison to other models. One such root water extraction model is O-R model, proposed by Ojha & Rai in 1996. The non-linearity in root water uptake is attributed to a parameter β contained in O-R model. The present study involves estimation of non-linear root water uptake parameter β of O – R model for wheat crop using Genetic Algorithm (GA) technique through inverse modelling. This requires numerical solution of soil moisture flow equation in unsaturated zone coupled with O-R model. Then the value of β is genetically optimized by reducing the difference between model estimated & experimentally found percentage soil water depletion in the root zone. The effectiveness of the developed model along with the optimization procedure is further verified using hypothetically generated percentage soil moisture depletion value corresponding to an assumed β value. The model is further implemented to wheat crop (Triticum) for estimation of its’ non-linear root water uptake parameter β.