Background Soil physical property is an important index to reflect soil erosion resistance, especially when soil particle composition is different, its sensitivity to rainfall and runoff is significantly different. At the same time, in the current research on soil erosion mechanism, more attention is paid to the representational relationship between various elements, but not enough attention is paid to the interpretation of their physical significance. Thus, to study the effect of soil properties on erosion characteristics and the physical significance of erosion rules can provide important theoretical support for the deep understanding of soil erosion mechanism and the optimization of evaluation model.

Methods This study applied indoor simulated rainfall experiment to analyzed the erosion characteristics of Ansai soil (soil A)and Suide soil (soil B) in loess hilly and gully region under the conditions of 90 mm/h rainfall intensity and four slopes (5°, 7.5°, 10° and 15°), and explained the erosion mechanism based on the mathematical relationship and physical significance.

Results 1) Compared with soil A, soil B has fast yield and high runoff, and is more prone to rill development and more serious erosion. 2) In general, the amount of erosion at the initial stage of runoff generation, sheet erosion stage and rill erosion stage increase with the slope. The sediment content of soil B in the sheet erosion stage is 1.09-4.47 times of that of soil A. The rill erosion stage of the former is 2.01 times that of the latter. The erosion amount of soil B in rill erosion stage is more than 98 % of the total erosion amount, and the average sediment content of soil B is 7.09-32.39 times of that in sheet erosion stage, while that of soil A is 96 % and 10.49 times, respectively. 3) The relationship between sediment yield and sediment content of the two soils can be expressed by y=ax+b. After optimization, the R² of the linear relationship can reach 0.98 or above. Based on the analysis of mathematical relationship and physical significance, slope a can be used to express the erosion capacity of runoff, and intercept b can be used to characterize the type and abundance of removable substances. Soil particle composition has an important effect on soil erosion. Soil with high clay and silt content has lower sediment concentration and lower soil erosion intensity.

Conclusions This study has important theoretical and practical significance both for deeply understanding the role of soil texture in slope erosion and for providing theoretical support for ecological protection.