IDENTIFICATION OF ERODED PHASES OF AN ALFISOL

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Abstract

The objective of this study was to determine the extent and location of eroded phases of an Alfisol at a cultivated site. The area was located on a backslope, with 5 to 10% slopes, which was to be used for tillage research. The extent of soil loss from cultural erosion was calculated using comparisons of soil properties with a forested site having similar soil, slope, and landscape characteristics. It was not possible to find a virgin site with similar characteristics. Most land in Southern Illinois has been cleared during the 190 years since initial European settlement. The interpretation of direct comparisons of A (and E) horizon thicknesses of the forested site with A (and E) material thicknesses in the Ap horizon of the cultivated area was complicated by the tillage equipment mixing Bt materials into the Ap over time. This resulted in pockets of Bt material in the Ap, a lighter matrix Ap color, thinning of the underlying Bt horizon, and an increase in the clay content of the Ap horizon. The depths to gray mottles and Bx horizon were also reduced at the cultivated site under a crop rotation that included forages for extended periods of time. The cultivated site was dominated by the moderately eroded phase of the Grantsburg (finesilty, mixed, mesic Typic Fragiudalf) soil. Based on paired transect comparisons with a forested site, changes in the clay content of the Ap, thickness of the Bt, and depth to gray mottles and Bx horizon, approximately 7.5 cm of soil (38% of the upper 20 cm of original soil) has been eroded from the cultivated site during the past 80 years.

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