Hydraulic Conductivity in a Clay Soil: Two Measurement Techniques and Spatial Characterization

Abstract

AbstractInfiltration, drainage, and chemical leaching are strongly influenced by the magnitude and spatial distribution of the field‐saturated soil hydraulic conductivity (Kfs). The Guelph permeameter (GP) method shows promise as an effective means for field measurement of Kfs and its spatial distribution, but its accuracy in medium‐ and fine‐textured soils is not well established. To further assess its accuracy and effectiveness, the GP method was compared with the auger hole (AH) method at the 0.5‐m depth at 68 grid locations in a texturally uniform silty clay soil that had stable but spatially variable structure. The two methods yielded similar geometric mean Kfs values (P < 0.001), as well as similar semivariograms. The two methods were also positively correlated (r = + 0.6565, P < 0.0001). We therefore concluded that the two methods gave equivalent estimates of Kfs at this field site, and that the GP method is capable of providing valid estimates of Kfs in at least some fine‐textured soils. The Kfs values were not correlated with soil texture, organic C content, or soil surface topography, but were negatively correlated (r = −0.7240 for GP method, r = −0.6070 for AH method, P < 0.0001) with antecedent volumetric water content (θa) measured in situ prior to the GP measurements using a down‐hole time domain reflectometry probe. The semivariogram for θa was similar to those for Kfs. These results suggest that the magnitude, range, and pattern of variability of the Kfs measurements were controlled primarily by the well‐developed and stable soil structure at the field site, rather than by texture, organic C content, or surface topography.