Experimental study on the influencing factors of infiltration characteristics of abandoned grassland on slope scale in the loess hilly and gully region

To explore the influence of various factors on the infiltration characteristics of abandoned grassland in the loess hilly and gully region of the Loess Plateau, a natural rainfall field observation method was used to study the influence of rainfall characteristics (rainfall, average rainfall intensity, rainfall duration and the maximum 30 min rainfall intensity (I₃₀)), antecedent soil water content, slope length (10 m, 20 m, 30 m, 40 m and 50 m), and vegetation coverage on soil infiltration characteristics. The grey correlation method was used to determine the dominant factors affecting the infiltration characteristics of the abandoned grassland. It was found that the infiltration amount increased significantly with increasing rainfall, rainfall duration and I₃₀ (R²>0.55, P < 0.01). The infiltration supplement coefficient decreased with increasing rainfall, I₃₀ and average rainfall intensity (R²>0.12, P < 0.05). The average infiltration rate increased with increasing rainfall intensity and I₃₀ (R²>0.53, P < 0.01). The infiltration amount and average infiltration rate decreased with the increase of antecedent soil water content, whereas the infiltration supplement coefficient increased with the increase of antecedent soil water content (R²>0.13, P < 0.05). The infiltration amount, infiltration supplement coefficient and average infiltration rate increased as the slope length increased (R²>0.56, P < 0.01). However, there was a critical slope length between 30 m and 40 m. Rainfall characteristics and slope length were the main factors affecting soil infiltration, and the effect of vegetation coverage on soil infiltration was not significant as the infiltration efficiency was high.