Sorptivity of a Slightly Moist Sandy Soil.

Sorptivity is a controlling parameter of water infiltration into soils. Many models exist to describe and predict sorptivity as a function of initial moisture content. Data from Washburn capillary rise experiments indicate that theoretical models of sorptivity are not accurate for the dry range of a sandy soil. In contrast to models which predict constantly declining sorptivity as initial moisture content increases from 0, we present data that indicates that sorptivity is highest at a certain moisture content higher than 0. Sorptivity for soils wetter than this water content decreases as expected from published models. Soils that are initially dryer than this threshold moisture content have lower sorptivity. We explain this phenomenon as an effect of film flow in slightly moist soils.