Unsaturated hydraulic conductivity of disturbed and undisturbed loam soil

Abstract

The soil water content-pressure head curve [θ(h)], described by van Genuchten, was used to predict some hydraulic characteristics of a Xeric torriorthent soil. Experimental data of volumetric soil water content (θ) and pressure head (h) were adjusted to the model, obtaining the three independent parameters used to calculate the unsaturated soil hydraulic conductivity (K) and soil water diffusivity (D). The K(θ) functions for disturbed and undisturbed soil samples were statistically different pointing to the effect of soil structure on soil water flow. For soil moisture values close to saturation, K values were ≥ 0.392 and ≥ 0.019 cm h-1, for undisturbed and disturbed soils, respectively. These low values would reflect the loam texture of the soil studied. In absence of roots capable of absorbing water, a supply of more than 4 L m-2 h-1 will lead to water-logging and losses through evaporation and runoff.