NONLINEAR ROOT-WATER UPTAKE MODEL

Sound irrigation management requires information about root-water upta ke patterns of different crops. In the existing literature, the extrac tion rate of sail moisture by the roots is assumed to be either consta nt or varying linearly with the root depth, during the crop period. Ho wever, both these models have limited application. With this in view, an empirical root-water uptake model in which the extraction rate vari es non-linearly with the root depth is proposed. Using experimentally obtained soil-moisture depletion values for non-limiting soil-moisture conditions, it is found that the proposed model performs better than the constant rate models and linearly varying rate models of root-wate r uptake. Also, constant as well as linear extraction-rate models are found to be particular cases of the proposed model. Based on simulatio ns :or limited soil-moisture conditions, it is also found that the fre quency of irrigation is sensitive to the use of root-water uptake mode ls.