Prediction of Infiltration into Layered Field Soils in Relation to Profile Characteristics

ABSTRACT USING an infiltration model derived from flow theory, we examined the effect of nature and extent of horizons in profiles of a Cecil soil (member of clayey, koalinitic, thermic family of Typic Hapludults) commonly encountered in the upper plain of the Southern Piedmont, upon infiltration and soil water distribution. We concluded that the characteristics and thickness of the surface soil horizon, which overlies a subsoil of significantly higher clay content and lower saturated hydraulic con-activity, determine infiltration and consequent distribution of soil water during a significant period of a rainfall event. The length of period may vary from 10 to 40 min for high intensity storms, depending upon initial profile water content, and for a longer period for dry soils and low intensity storms. Usually, the B2 horizon of the Cecil soil begins to regulate infiltration after 30 to 40 min. The duration of these periods assumes that raindrops or wetting have an insignificant effect upon the surface hydraulic characteristics. The model adequately describes infiltration into a grass covered plot. However, under intense rainfall, e.g., 0.2 cm/min, modified surface hydraulic characteristics may prevent a good estimate of infiltration by the model if the surface canopy is limited and unless the model imposes an attenuation of infiltration.