Development and evaluation of a soil water evaporation model to assess theeffects of soil texture, tillage and crop residue management under field conditions

A number of mathematical models to predict soil water evaporation are avail able in the literature which generally require complex input data. In the p resent study, a simple parametric model has been developed by coupling exis ting and newly developed equations to assess soil water evaporation and dra inage under field conditions in relation to potential evaporation rate, soi l texture, time and depth of tillage and crop residue management. The model has moderate input data requirements and predicts well the effects of till age and crop residue management practices on soil water loss (evaporation drainage) with multi-drying and -wetting cycles prevailing under natural c onditions. The root mean squares of deviations between observed and predict ed cumulative water loss at different periods of study were 0.82, 2.04 2.31 and 1.74cm for untreated, residue-mulch, tillage and residue-incorporated treatments, respectively. Simulation analysis on cumulative evaporation and evaporation rate has shown that the evaporation reduction with different c ombinations of tillage and crop residue followed the order of residue-under cut > residue-mulch > residue-incorporated,tillage. Thus, the magnitude of beneficial effects of crop residues and tillage on soil water evaporation r eduction are associated with amount of residues, mode of residue management (mulched or incorporated in the soil) and time and depth of tillage.