Monday, November 13, 2006

Soil Water Retention Curves of Two Wettable Soils and Their Matched Hydrophobized Counterparts.

Dedrick Davis, Robert Horton, and Joshua Heitman. 2543 Agronomy Hall, Iowa State University, Ames, IA 50011

The soil water retention curve is a useful tool for understanding the basic relationship between soil moisture content and the energy associated with the retained water. Most previous studies have focused on the wet end of the soil water retention curve while little attention has been given to the dry end of the soil water retention curve where surface adsorption is the critical component in determining the amount of water retained.  In this study we examine the dry end of the soil water retention curve and the hysterestic behavior associated with two wettable soils and their matched hydrophobic counterparts.  The soils used are Hanlon sandy loam and Ida Silt loam.  Soil samples consist of natural, wettable samples as well as dimethyl silane treated hydrophobized samples.  The soil water retention curves are measured by vapor equilibration of the hydrophobic and hydrophilic soil samples over saturated salt solutions of known osmotic potentials.  During vapor equilibration the initially moist samples dry and the initially dry samples wet.  We report the effects of wettability and wetting and drying history on soil water retention of these soils.