Effect of Erosion and Landscape Position on the Productivity of Piedmont Soils

The objective of this study was to determine the effect of past accelerated erosion in the North Carolina Piedmont on soil physical and chemical properties and soil productivity, and to determine the relationship between soil productivity, soil erosion, and landscape position. Data from five Piedmont fields were collected over a 2-yr period. Within each field, plots were located on all erosion classes and landscape positions present. Definite relationships between erosion class and soil physical and chemical properties were observed. Clay content increased approximately 10% for each erosion class change from slight to moderate to severe. Organic matter content tended to be higher on the more eroded sites. Differences in topsoil depth among erosion classes in a given field ranged from 2.4 to 8.7 cm and the severely eroded areas were always significantly shallower. Available water-holding capacity of the A horizon (g g⁻¹) always was slightly higher on the more eroded sites. Available P decreased sharply with erosion severity but all sites had levels ≥ 17 g P m⁻³ which is considered adequate. The highest corn grain yields were usually obtained on the moderately eroded sites as compared to the slightly and severely eroded areas. This was particularly true in 1981 which was a dry year. In a more favorable year (1982) with regard to amount and distribution of growing season rainfall, the yield differences among erosion classes were less. The differences in corn grain yield among landscape positions were much more consistent than yield differences among erosion classes. Those landscape positions that received water from higher elevations produced the highest yields. Because landscape position and erosion severity are not mutually exclusive, we believe that much of the published data dealing with the effects of erosion on soil productivity are confounded by the effect of landscape positions on soil erosion.