Erosion Effects on Productivity of Cecil Soils in the Virginia Piedmont
1989
Thomas, P. J. | Simpson, T. W. | Baker, J. C.
A study was initiated in two counties in the southern Virginia Piedmont to assess the effects of erosion on soil properties and crop productivity. Plots were established in farmer-cooperator fields on slightly, moderately, and severely eroded Cecil soils (clayey, kaolinitic, thermic Typic Kanhapludults). The Ap horizon decreased as severity of erosion increased, although no differences were observed for Bt and solum thicknesses. Clay content of the Ap horizon increased as the severity of erosion increased. Increases in clay content were reflected by several soil properties. The volumetric water contents at −10 kPa and −1500 kPa increased with clay content of the Ap horizon, but the differences in plant available water remained at 0.09 m³ m⁻³. Thus, the effect of erosion on plant available water in both the Ap and Bt horizons was negligible. Cation exchange capacity was higher on the severely eroded sites. Exchangeable Al, expressed as either percent of the exchange complex or as concentration in the soil, was lower than expected and had no apparent adverse effect on yields. Available P decreased with severity of erosion and was significantly correlated with soybean [Glycine max (L.) Merr.] grain yield. Grain yields were greater on the slightly and moderately eroded sites compared to the severely eroded sites. This was attributed to levels of available P in the slightly and moderately eroded soils that were above the 18 mg kg⁻¹ critical P level for optimal crop growth, while available P was below 18 mg kg⁻¹ in the severely eroded soils. The magnitude of difference between noneroded and eroded soils may be difficult to assess because of the scarcity of uneroded upland Piedmont soils by which such comparisons are made. Thus, estimates of the impact of the severity of erosion in the Piedmont may be difficult to establish.
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