The impact of surface gravel cover and slope gradient on splash and interrill erosion rates in two contrasting soils

Due to low plant cover in arid and semi-arid regions, surface gravel cover (SGC) plays an important role in soil erosion control. The aim of this study is to investigate the effect of SGC and slope gradient on splash as well as interrill erosion in two contrasting soils. For this purpose, a constant rain was simulated on two soils namely sandy and cropland with different aggregate size distributions at four slope gradients including 0.5, 2, 5 and 10 % and five levels of SGC including 0, 5, 10, 20 and 40 % each at three replicates. Through producing a rain intensity of 35 mm/h for 35 min duration on a 0.35 m by 0.35 m test area, both splash (downward, upward and the total splashed material) and interrill erosion rates were measured. Result showed that with increasing SGC in both soils, the downward, upward and the total average splash increased, significantly. However, the downward splash rate was higher than the upward splash rate. With increasing SGC from 0% (control) to 5, 10, 20 and 40 %, the downward splash rate decreased for the sandy soil by 12.9%, 25.3%, 35.7% and 47.7%, and for the cropland soil by 13.9%, 25.4%, 37.0% and 49.4%, respectively. Regarding the interrill erosion rate, the corresponding reduction percentages for the sandy soil were 13.5%, 26.4%, 33.3% and 46.4% and for the cropland soil were 12.9%, 30.7%, 37.3% and 45.9%, respectively. Moreover, nonlinear increases in the interrill and splash erosion rates were found at steeper slopes. Due to lower cohesion and greater detachability of sandy soil, it exhibited higher erosion rates than those for the cropland soil. The findings of this study revealed that in the presence of SGC, both splash and interrill erosion rates will reduce, significantly.