MEASUREMENT OF SATED HYDRAULIC CONDUCTIVITY OF SURFACE SOIL IN THE FIELD WITH A SMALL-PLOT SPRINKLING INFILTROMETER

Abstract

The purpose of this study was to determine the sated (near-saturated) hydraulic conductivity, K, of surface soil in the field. With K as a parameter, an equation describing cumulative water runoff from a small-plot sprinkling infiltrometer was developed from an empirical infiltration equation matched to Green-Ampt infiltration theory for constant-intensity water application; also incorporated was a fixed-average static concept of surface water storage on the small soil plot. To evaluate K, this runoff equation was fitted by least squares to field data from a small-plot (1.16mx1.16m) sprinkling infiltrometer on four combinations of soil type and cover: Clermont and Cincinnati silt loam (grass), and Chelsea sandy loam (grass and fiberglass). The runoff equation fitted the field data very well, especially at times greater than 10-15min after the first appearance of water runoff. The order of the mean K values for the four soils-cover combinations was: Chelsea-grass>Chelsea-fiberglass>Cincinnati-grass>Clermont-grass, which is compatible with the physical characteristics of these soils and covers. Of the various differences between mean K values, half were statistically significant. The fixed-average static surface-water storage behaved in reasonable fashion, both physically and statistically, and in regard to site slope and plot cover.