Soil Hydraulic Properties in a Cassava Field as a Function of Soil Dry Bulk Density

Abstract

This study is being conducted at a commercial arable flat area in northeast part of Thailand. In order to estimate the heterogeneity of soil hydraulic properties such as soil water retention, water diffusivity, and hydraulic conductivity with dry bulk density, soil hydraulic properties were measured in the laboratory for repacked soil samples compacted to pre-determined dry bulk densities. The experimental data was fitted to the van Genuchten′s and Mualem′s models using the RETC optimization computer code. Effects of dry bulk density on soil hydraulic properties were deduced from variations in the van Genuchten′s and Mualem′s models parameters. The correlation coefficients between dry bulk density and the model′s parameters were between 0.91-0.99. The van Genuchten′s and Mualem′s models of soil water retention and hydraulic conductivity, respectively, were modified to be a function of original parameters and dry bulk density. Using these modified models and distribution of dry bulk density in the field, distribution of soil hydraulic properties can be predicted.