S. N. Prasad
University of Mississippi

M. J. M. R?mkens

          Infiltration is a highly complex process which, over the years, has received much research attention. However, it remains a difficult component to estimate runoff and soil erosion predictions. A major reason for this difficulty is the highly complex nature of soils as manifest by the spatial and temporal variation of the soil matrix, heterogeneity of the soil profile with depth, and the instability of the soil matrix during wetting and drying processes.

          The experiments of this study focus on the role of cracks in infiltration processes of Mississippi Delta soils. The objective is to develop relationships that partition rainfall into surface runoff and infiltration for evaluations of chemical movement from agricultural fields.

          Ongoing experiments have shown that crack development (depth and size) increased upon drying following each of a series of rainstorms of 3 h duration and 30 mm x h^-1 intensity applied to an initially air-dry soil bed of Sharkey soil sieved to pass a 2 mm screen and of 2% slope. Crack development on soil beds with seal development had both vertical and horizontal cracks (curling up phenomenon). Infiltration and incipient ponding time increased with increasing crack formation. Following closing of cracks upon wetting, infiltration rates were not detectable on soil beds with seal development The cracking pattern appeared to be similar following each rainstorm and at the same general location.

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