Characterizing Soil Hydraulic Properties Under Varied Land Use.

Land use impacts on soil quality may be characterized by changes in soil hydraulic properties. These properties directly influence infiltration as well as runoff and erosion. Soils in the major land resource area, the Southern Mississippi Valley Silty Uplands (MLRA 134), have high erosion potential and land use practices affect soil loss. We measured hydraulic properties of the dominant soil (Memphis silt loam) in MLRA 134 on hardwood forest, pasture, and pine forest in Coles Creek watershed. Unconfined infiltration measurements were carried out in a rang of descending tensions, 15, 10, 6, 3 cm of water, using 20 cm disc tension infiltrometers on the soil surface and the 15-cm soil depth.  The Wooding’s equation for steady state flow was used to estimate soil hydraulic conductivity K(h). Soil cores were also extracted from the 0-15 and 15-30 depths to determine bulk density (r_b). The WP4 PotentiaMeter® was used to measure soil water retention values, q(h), at the two soil depths and the van Genuchten-Maulem model was fitted to the experimental data using the optimization computer code, RETC.  Results from this study showed significantly higher K(h) in the hardwood forest, followed by the pine forest for both experimental and fitted data (P<0.05). The van Genuchten-Maulem model showed a good fit to the experimental water retention data for all land use.