Background Soil erosion is very serious in the Pisha-sandstone area of Inner Mongolia Ordos, and rainfall erosion is an important factor causing soil erosion in Pisha-sandstone, while rainfall splash is the main erosion mode of soil at the early stage of rainfall. Since splash dispersion changes soil particles in the parent material, it is important to investigate the sorting law of rainfall splash on the particle size of loose Pisha-sandstone and the sensitivity to the sorting of particle size at all levels to reveal the mechanism of erosion of loose Pisha-sandstone at the beginning of rainfall.

Methods Indoor artificial rainfall simulation was used to conduct spattering experiments on loose Pisha-sandstone. In order to reveal more clearly and intuitively the sorting degree of each particle size in the splash erosion samples by rainfall intensity and slope, the magnitude of the absolute value of the change rate was introduced to indicate the variation of the number of particles in each grain size interval, and the trend of the variation was reflected by the positive or negative rate of change.

Results The slope and rainfall intensity are the main influencing factors for the occurrence of spattering erosion of Pisha-sandstone. On the slope with slope less than or equal to 20°, rainfall intensity is the most sensitive factor for splash erosion of loose Pisha-sandstone, in which the percentages of medium sand, fine sand and very fine sand particles increase with the increase of rainfall intensity, and the percentages of up-slope quantity are always larger than those of down-slope; while the percentages of powder sand quantity decrease with the increase of rainfall intensity, and the percentages of up-slope quantity are smaller than those of down-slope. In the slope with slope greater than or equal to 30°, the sensitive factors of spattering of loose Pisha-sandstone are slope and rainfall intensity, and the increase of rainfall intensity makes the size of soil particles that can be migrated gradually increase; when the slope and rainfall intensity are the same, the percentage change of the number of fine sand particles is the largest, and the effect of spattering on the sorting of fine sand is the most significant, then the medium sand, very fine sand, and silty sand in order.

Conclusions The severity of spatter erosion occurring in loose Pisha-sandstone is the result of the combined coupling of multiple factors such as rainfall intensity, slope, and soil particle size. Among them, rainfall intensity and ground slope have the greatest effect, but the sensitivity of these two factors can vary depending on the size of different particles.