Temporal Variability of Soil Hydraulic Properties with Wetting and Drying Subsequent to Tillage 1

Modeling of water movement in soils requires mathematical representation of hydraulic conductivity and water retention functions. Hydraulic properties of soils are expected to vary over time during a cropping cycle, especially soon after tillage. Field experiments were conducted on two soils, a Typic Torrox and a Vertic Haplustoll, to evaluate the effect of soil deformation from repeated wetting and drying on soil properties such as hydraulic conductivity, sorptivity, and the water content-suction relationship. Hydraulic conductivity near saturation was the most sensitive measure of temporal changes of hydraulic properties, decreasing 100-fold with wetting and drying after tillage. Sorptivity measured with negative head, a simple and rapid method, was also sensitive to temporal changes and was judged the most appropriate for variability studies requiring a large number of samples. The impact of temporal changes in hydraulic functions on soil-water movement was demonstrated by a comparison of water content profiles predicted with a simulation model using input functions obtained before and after irrigation. Additional Index Words: sorptivity, water retention, tropical soils, soil shrinkage, compaction. View complete article To view this complete article, insert Disc 4 then click button8