Saturated hydraulic conductivity of soils in the Southern Piedmont of Georgia, USA: Field evaluation and relation to horizon and landscape properties

Saturated hydraulic conductivity (K-s) is one of the soil properties used most often to predict soil behavior and suitability for a variety of uses. Because of the difficulty in K-s measurement and its variability with depth and across the landscape, K-s is commonly predicted from other more easily evaluated properties including texture, clay mineralogy, bulk density, pedogenic structure and cementation. Of these, texture and pedogenic structure are most commonly used to estimate K-s, but the reliability of these estimates has not been evaluated for common soils in the Southern Piedmont of Georgia. Thus, the objectives of this study were to evaluate K-s, for major horizons in soils and landscapes in the Georgia Piedmont and to relate K-s to morphological properties of these horizons. Ten sites across the region were selected, and 21 pedons arranged in three transects were described from auger holes and pits. For each pedon, K-s was measured in upper Bt horizons, at 140 cm below the surface (Bt, BC, or C horizon), and at a depth intermediate between the shallow and deep measurements (Bt, BC, or C horizon) with a constant head permeameter. The K-s of individual horizons ranged from 1 x 10(-8) to 2 x 10(-5) m s(-1). At six of 10 sites evaluated, clayey upper Bt horizons had higher K-s than deeper horizons with less clay. This difference was attributed to weaker structure in the deeper BC horizons. Structural differences did not explain all variation in K-s with depth, however. Other soil and landscape properties including parent material composition, colluvium on lower slope positions, C horizon cementation, and depth of soil development also affected K-s of horizons in these soils and should be used to better estimate K-s. (C) 2007 Elsevier B.V. All rights reserved.