Assessment of detachment and sediment transport capacity of runoff by field experiments on a silt loam soil

The detachment capacity ( D c ) and transport capacity ( T c ) of overland flow are important variables in the assessment of soil erosion. They determine respectively the lower and upper limit of sediment transport by runoff and therefore control detachment and deposition pro‐cesses. In this study, the detachment and transport capacity of runoff was investigated by rainfall simulations and overland flow experiments on small field plots. On the bare field plots, it was found that T c was strongly related to total runoff discharge. This was also observed for the plots covered by maize residues, but T c was less due to the lower runoff velocity. A simple regression equation was derived to estimate T c for both bare and covered soil. Comparing our observations with T c equations mentioned in the literature revealed that T c equations based on laboratory experiments overestimated, on average, our measurements. Although T c can be assessed more easily in laboratory experiments, the applicability of the results to field conditions remains questionable. Detachment by runoff was also related to total runoff discharge. The D c values were, however, 4–50 times smaller than the T c at corresponding high and low runoff discharge. This indicates that detachment by runoff constitutes only part of the transported sediment. Interrill erosion supplies an important additional amount of sediment. In this study, however, only sealed soils were considered. In the case of freshly tilled, loose soils, the D c of runoff may be larger, resulting in a larger contribution to the total soil loss. Copyright © 2008 John Wiley & Sons, Ltd.