SIMULATION OF SOIL-MOISTURE PROFILES FOR WHEAT IN BRAZIL

A computer model to estimate components of the water balance for a cro pped, layered soil profile without the influence of water table is des cribed, Infiltration and soil water redistribution are governed by Dar cy's law and evapotranspiration is partioned into three components: so il evaporation, transpiration, and evaporation of intercepted precipit ation on the crop canopy, Those terms depend on the atmospheric demand , soil water availability, root water extraction and crop growth chara cteristics. In addition to evapotranspiration, model output also inclu des fluxes, pressure head, and soil moisture at different depths of th e profile and runoff and pending at the soil surface. The model was va lidated for a subtropical humid region in Parana State, Brazil, under six wheat cropping periods. Predictions of soil water contents and eva potranspiration were in close agreement with field data. The model was considered appropriate for long term simulations of the water balance and irrigation requirements.