The determination of field‐saturated hydraulic conductivity in some Scottish soils using the Guelph permeameter

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Abstract
Soil hydraulic conductivities are frequently required for process‐based modelling of the soil water regime. Field‐saturated hydraulic conductivity was measured with the Guelph permeameter in 10 soil series with a range of structures and textures. The permeameter offers a range of options for calculating conductivities depending on soil conditions, particularly homogeneity of pore distribution within each horizon. However, even horizons described as massive or apedal were not sufficiently homogeneous to satisfy the boundary conditions entirely.Hydraulic conductivities were calculated by the one head, fixed α* procedure; α* is an index of capillarity. No direct correlations were found between hydraulic conductivity and land use. However, the average hydraulic conductivity of coarse textured topsoils which were mainly under arable agriculture was less than that of the finer textured topsoils largely under grassland. Even limited structural development increased the hydraulic conductivities of fine textured, compact subsurface horizons. It is important to match the adopted procedure to the soil conditions both during the determination of flow rates in the field and in the subsequent analyses.