Response of spatial variability of soil physical properties to soil erosion in purple soil slope farmland

In order to study the effects of soil erosion on spatial variability of soil physical properties in farmlands with different lengths and slopes, the response of spatial variability of soil physical properties to soil erosion was explored in the Sichuan Basin of China, with topography measurement, 137Cs tracer method and analysis of soil physical properties. The results showed that tillage erosion, which was the dominant erosion process on the short slopes with the gradients of 16.6%～25.1%, played an important role in redistributing soil and resulted in no significant variation in soil physical properties (i.e., soil texture and bulk density) of tillage layer along the slope (CV＜6.3%). Meanwhile, the soil physical properties of tillage layer had insignificant correlation with 137Cs contents due to tillage erosion. On the steep slope (35.6%), water erosion was the predominant erosion process due to reforestation, with evidence of 137Cs contents correlated closely with soil physical properties of tillage layer. Furthermore, on the long slope (10.1%), water erosion with separation and transport capacity was the predominant erosion process, which resulted in significant variation in soil physical properties with 137Cs contents, but there was no significant correlation between bulk density and 137Cs contents. Soil depth was affected both by tillage erosion and water erosion in slope farmlands in the Sichuan Basin of China. The erosion resulted in the fact that the thinnest soil layer was present at the summit and upper slope positions, and there was the thickest soil layer at the foot of the slope. In general, soil depth increased towards the downslope direction. Therefore, due to the differences in the predominant soil erosion process the soil physical properties varied with slope lengths in the Sichuan Basin.