A simple empirical model of root water uptake

Abstract

An empirical sink function describing water extraction by roots is proposed. Water uptake is given as a function both of the potential transpiration rate and a weighted stress index which accounts for the effects of the vertical distributions of roots and soil water content. The model was tested in the field using measurements of water content in a clay soil in which oats, spring rape and mustard crops were grown under mobile shelters. Measured changes in soil water content were considered primarily due to root water uptake, since recharge was prevented and the redistribution of water assumed negligible. Best-fit parameter values were found by optimization during one experimental year. Model predictions compared well with measurements in two further years ( r 2 values of 94 and 81%), with no change in the optimized parameter input values.