The effect of slope length on the amount and size distribution of eroded silt loam soils: short slope laboratory experiments on interrill erosion

The data of rainfall simulation experiments on a sandy loam and a loamy sand were compared to assess the effect of slope length on the soil loss from short slopes (between 0.3 and 0.9 m). The total soil loss and the aggregate size distribution in the total soil loss were determined after 90 min of rainfall with rainfall intensities between 22.0 and 78.5 m h−1. The experimental results indicated that the slope length effect is different for the two soils. Although for both soils the total soil loss increased with increasing slope length, the soil loss per unit slope length increased with increasing slope length only for the sandy loam (soil 1) and decreased with increasing slope length for the loamy sand (soil 2). The difference in slope length effect between the two soils was also reflected in the aggregate size distribution in the soil loss. The different aggregate sizes displayed different relationships between soil loss and slope length. For the loamy sand the slope length effect was less for the large aggregate sizes which contained more sand than the original soil. For both soils the slope length effect was most pronounced for the aggregate sizes smaller than 0.05 mm.