Determination of withdrawal of water from soil by crop roots as a function of depth and time

Abstract

Theory is presented to permit the calculation of water withdrawal by plant roots at any depth in soil as a function of time, without neglect of water movement in the soil. Such neglect may be a source of error in using other approaches to this problem. The method proposed requires a knowledge of the moisture and hydraulic conductivity characteristics of the soil as a function of depth. When this theory was applied to data from an irrigated cotton crop, it was shown that the maximum rate of water withdrawal by roots was between the soil surface and 25 cm, and that rates were relatively low below 30 cm. The withdrawal pattern is discussed in relation to potential evaporation and the water status of the crop.