Surface sealing in Coastal Plains loamy sands
1991
Radcliffe, D.E. | West, L.T. | Hubbard, R.K. | Asmussen, L.E.
Soil surface seals may consist of a dense surface skin seal and/or a washed-in layer of dispersed clay just below the surface. Work in Israel has shown that when clay contents are below about 20%, the seals that form are relatively permeable. In Georgia, soils of the Piedmont region with clay contents above 10% can form low-permeability seals. Our objective was to determine if the more sandy soils of the Coastal Plain region would form seals and, if so, to describe the morphology of these seals. Infiltration was measured using a rainfall simulator on bare and straw-covered tilled soil at six sites on three loamy sands. The three soils used were Tifton (fine-loamy, siliceous, thermic Plinthic Kandiudult), Carnegie (clayey, kaolinitic, thermic Plinthic Kandiudult), and Clarendon (fine-loamy, siliceous, thermic Plinthaquic Paleudult). Final infiltration rates were significantly lower in the bare soil at all but one site, indicating that sealing occurred. Final infiltration rates were not as low as those observed in soils from the Piedmont region of Georgia, probably due to the lower clay content of the Coastal Plains soils. Thin-section micrographs suggested that these seals formed due to surface disruption with raindrop impact. Although grains that had been stripped of clay and oxides were observed at the surface, no distinct zones of clay and oxide concentration (washed-in layers) were observed. Size and spatial relationships of the areas of stripped grains suggested that they had been transported and redeposited rather than develop in place.
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