Anisotropy of a Fragipan Soil: Vertical vs. Horizontal Hydraulic Conductivity
1987
Dabney, S. M. | Selim, H. M.
Undisturbed core samples were obtained in vertical and horizonal directions from surface and subsurface horizons of an Olivier silt loam (Aquic Fragiudalfs, fine-silty, mixed, thermic) in order to test for anisotropy. Saturated hydraulic conductivity, bulk density, penetrometer resistance, and volumetric moisture content at soil matric potential of 30 J kg⁻¹ were measured. Hydraulic conductivity values within the Ap did not differ in horizontal and vertical sampling directions. However, within the Btx1 horizon, measured conductivity values were three times greater in vertical than in horizontal directions. This was attributed to the primarily vertical orientation of flow-restrictive zones within the fragipan. Bulk density and moisture content differed between surface and subsurface horizons, but were not influenced by direction of core sampling. Penetrometer resistance did not differ between horizons or sampling direction, but was significantly greater in brown than in grey areas of the fragipan. The results of this study have relevance to models of soil water flow and the sampling methods described should be applicable to testing for anisotropy in other soils.
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