Effect of Stones on the Hydraulic Conductivity of Relatively Dry Desert Soils

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Abstract
The objective of this study was to determine whether moisture transmission properties of stony soils could be evaluated using samples of the same soil in which the stony fraction (> 2 mm) had been excluded. Experiments were conducted in the laboratory on soil columns with and without stones. Unsaturated hydraulic conductivity (K) was measured with a transient outflow method over the matric potential range of −0.05 to −50 bars using tensiometers and soil psychrometers. The soils studied were Rock Valley gravelly loamy sand (Mojave Desert, Nevada) and Tubac and Rillito gravelly sandy loams (Sonoran Desert, Arizona). On a weight basis, these soils contain up to 40% stones > 2 mm in diameter.If expressed as a function of matric potential, hydraulic conductivity values were similar, with or without stones. Soil water potential as measured by tensiometers or by thermocouple psychrometers is not affected by stones because these instruments respond to moisture changes in the soil portion only. When K was expressed as a function of volumetric water content, the apparent conductivities were higher for a given water content when stones were present. A simple correction of water contents of stone‐free samples, based on the stone volume of each soil, adequately accounted for differenecs observed when water contents were computed on a total volume basis.
Funding Information
  • National Science Foundation
  • Center for Ecology and Environmental Technology, University of Louisiana at Lafayette (539)

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