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 innortheast part of Thailand. In order to estimate the heterogeneityof soil hydraulic properties such as soil water retention, waterdiffusivity, and hydraulic conductivity with dry bulk density, soilhydraulic properties were measured in the laboratory for repackedsoil samples compacted to pre-determined dry bulk densities. Theexperimental data was fitted to the van Genuchten′s and Mualem′smodels using the RETC optimization computer code. Effects of drybulk density on soil hydraulic properties were deduced from variationsin the van Genuchten′s and Mualem′s models parameters. The correlationcoefficients between dry bulk density and the model′s parameterswere between 0.91-0.99. The van Genuchten′s and Mualem′s models ofsoil water retention and hydraulic conductivity, respectively, weremodified to be a function of original parameters and dry bulk density.Using these modified models and distribution of dry bulk densityin the field, distribution of soil hydraulic properties can be predicted.