Interpreting Infiltration Measurements of a Vertisol: Effects of Land Use and Landscape Position.

It is known that K_sat values have high spatial variation across landscapes but little is known about how to interpolate a few measurements of K_sat across a landscape and account for this inherent variation.  Variations in soil structure, macropores (especially in shrinking and swelling soils), land uses (plant roots), and soil development can cause large variation in K_sat within one soil type.  It is important to characterize the impacts of land use and terrain attributes on K_sat rates to properly understand how land use, management, and human activity affect local and regional hydrology and water quality. Particularly, hydrology models, which assess the impact of land management decisions, commonly ignore the impact of management and landscape position on soil infiltration and K_sat because there is little information on how to change K_sat under different topography and land uses for a given soil type.  The overall objective of this research is to understand how infiltration and soil K_sat vary over a Vertisol under different land uses and terrain attributes and to extend this knowledge to develop a smart-sampling strategy for collecting future K_sat data.  To achieve this goal, soil infiltration measurements are collected across catenas of Houston Black clay (fine, smectitic, thermic Udic haplusterts) and Heiden (fine, smectitic, thermic Udic haplusterts) under different land uses. Measurement locations were selected to account for variation in land use and terrain attributes (slope, contributing area, wetness index).  Infiltration results will be analyzed using Fishers protected LSD using soil landscape position and electrical conductivity values. Regression analysis of K_sat and soil characterization data will also be presented. This knowledge will be used to enhance current data bases that provide information on soil hydraulic properties for use in hydrology models.