Effect of soil loosening on the hydraulic properties of a duplex soil
1992
Jayawardane, N.S. | Prathapar, S.A. (Commonwealth Scientific and Industrial Research Organisation, Griffith (Australia). Div. of Water Resources)
In a duplex, transitional red-brown earth, the relationships between hydraulic conductivity K, diffusivity D, soil water potential (SWP) and volumetric water content (VWC) in different soil layers were evaluated. Replicated large undisturbed and repacked cores of 0.75 m diameter and 1.35 m deep, located in a lysimeter, were used. The undisturbed soil showed similar soil water characteristics in all soil layers at depths greater than 0.25 m. In contrast, K at high SWP was significantly lower in the upper subsoil, 'throttle' layer with high clay content, compared with the deeper soil layers. The repacking of the soil to a lower bulk density caused an increase in K at high SWP values. The decrease in diffusivity D with reduction in VWC was less marked in the repacked soil compared with the undisturbed soil. The calculated values of macroscopic capillary length decreased and characteristic pore radius increased, reflecting the changes in pore sizes and hydraulic conductivities due to soil loosening. However, at any given supply and antecedent SWP, the sorptivity was greater in the loosened soil due to larger changes in water content and hydraulic conductivities. The potential application of these soil properties in evaluating water flow in undisturbed or loosened soil is briefly discussed.
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