Predicting Seasonal Irrigation Water Requirements on Coarse-Textured Soils

Abstract

ABSTRACT Awater-balance model has been developed for predicting seasonal irrigation water requirements. The model treats the soil as a multi-layered water storage reservoir. Reservoir capacity is defined by soil water desorption data, rate of root growth, and effective rooting depth. Water withdrawal rate or crop water use is determined from pan evaporation data corrected to potential ET and converted by consideration of plant growth stage. Rainfall is partitioned into runoff, effective precipitation, and deep percolation. Field data from corn and soybeans during the seasons 1979-81 on two soil types were used for verification. The mean absolute difference between predicted and measured seasonal irrigation water requirements was 16%. Simulation data were fitted to frequency distributions, and irrigation requirements are expressed in terms of probabilities.