Tillage along slopes creates furrows similar to rills which exposes the soil surface directly to raindrop impact (RI) especially in semi-arid regions. In order to quantify the effect of RI on soil physical degradation and rill detachment we determined the change of soil aggregate stability, bulk density, surface resistance and rill detachment in semi-arid soils. Toward these some dominant soils including silt, silty clay, clay, sandy clay and loamy sand were exposed under rainfall impact at four slope gradients (5, 10, 15 and 20%). The laboratory experiments were set up at two soil surface conditions: with and without RI in a flume under simulated rainfalls with an intensity of 90 mm h⁻¹. Four rills with parabolic cross sections, 10 cm width and 4 m length were installed along the flume. Results indicated that the soils are physically degraded (aggregate breakdown, soil compaction and surface resistance) by RI. The rate of physical degradation processes was significantly influenced by the soil type and slope gradient. The soils with higher water-stable aggregates such as sandy clay showed lower physical degradation symptoms. The susceptibility of these soils to physical degradation processes increased with increasing slope gradient. Soil detachment through concentrated flow under RI was affected by the soil physical degradation rate, which in turn was controlled by the two variables i.e. soil type and slope gradient. However the direct effect of RI act in rill detachment (rainfall-driven force) increased rill detachment. As a conclusion, the rill detachment showed higher dependency to RI than soil physical degradation processes. This study revealed that the importance of maintaining the soil surface cover for controlling the negative effects of RI in the soil physical degradation as well as rill detachment especially in semi-arid soils with lower aggregate stability and under steep slopes.

沿斜坡耕作会产生类似于细沟的犁沟，使土壤表面直接暴露于雨滴冲击 (RI)，尤其是在半干旱地区。为了量化 RI 对土壤物理退化和细沟脱离的影响，我们确定了半干旱土壤中土壤团聚体稳定性、容重、表面阻力和细沟脱离的变化。对这些主要土壤包括粉砂、粉砂质粘土、粘土、砂质粘土和壤质砂在四个坡度梯度（5%、10%、15%和20%）的降雨影响下暴露。实验室实验在两种土壤表面条件下进行：在强度为 90 mm h ^{-1 的}模拟降雨下的水槽中，有和没有 RI. 沿水槽安装了四个具有抛物线横截面的细沟，宽 10 cm，长 4 m。结果表明土壤被 RI 物理降解（骨料分解、土壤压实和表面阻力）。物理降解过程的速率受土壤类型和坡度梯度的显着影响。具有较高水稳定性团聚体的土壤如砂质粘土表现出较低的物理降解症状。这些土壤对物理降解过程的敏感性随着坡度的增加而增加。RI 下通过集中流的土壤脱离受土壤物理降解速率的影响，而后者又受土壤类型和坡度梯度两个变量的控制。然而，RI 对细沟脱离的直接影响（降雨驱动力）增加了细沟脱离。综上所述，与土壤物理退化过程相比，细沟脱离对 RI 的依赖性更高。这项研究表明，保持土壤表层覆盖对于控制 RI 对土壤物理退化和细沟脱离的负面影响的重要性，尤其是在团聚体稳定性较低的半干旱土壤和陡坡下。