Particle Size of Interrill‐eroded Sediments from Highly Weathered Soils

<jats:title>Abstract</jats:title> <jats:p> Fifteen highly weathered Alfisols and Ultisols from Georgia were used in runoff/erosion pan studies to delineate sediment character istics of interrill‐eroding soils and their relationship to soil particle size. Simulated rainfall was applied to the pans at 11.2 cm h <jats:sup>−1</jats:sup> , and runoff and sediment parameters were measured at 5‐min intervals for 25 min. Runoff rates and sediment concentrations varied consistently over time for the soils used, with concentrations increasing until peaking at 10 to 15 min, then decreasing as crust formation caused surface consolidation and decreased detachability, despite continued high runoff rates for most of the soils. Sediment particle size became finer after the initial sampling period, and was dominated by silt‐sized particles, with lesser amounts of primary clay and sand. Silt‐sized particles in the sediments were related statistically to a measure of water‐dispersible (0.5‐h shaking) soil silt, whereas primary sediment clay was related to both water‐dispersible (36‐h shaking) and total soil clay. Dispersible and total soil clay were also correlated with sediment concentration and soil loss rate, emphasizing the role of clay and its dispersibility in erosion and crust formation on these soils. A quadratic equation using soil clay described sediment clay content, showing greater relative enrichment of primary clay in sediments from sandy vs. clayey soils. The high proportion of easily transportable sediment generated by interrill erosion on these soils poses a serious environmental problem in areas of active soil erosion. </jats:p>