Soil infiltration capacity and its influencing factors of different land use types in Karst slope

In order to ascertain soil infiltration capability and analyze its influencing factors in Karst region, this paper studied soil infiltration curves and their characteristics of four land use patterns in a Karst hill by using infiltration ring. Soil bulk density, porosity, soil particle-size distribution, water-stable aggregates and organic matter were also measured. The study indicated that, soil infiltration rates and permeability in surface layers of the four land use types were similar, but big difference existed in sub-layers between dry lands and other land use patterns. Land utilization was an important factor which should be responsible for the variation of infiltrability. Stable infiltration rates in soils, under natural conditions, were very high; cultivation and deforestation appeared to increase soil bulk density, while also reducing organic matter, water-stable aggregates and infiltration rates. Initial and stable infiltration rates changed in the same order: shrub land>orchard>grass land>dry land. Mean value of stable infiltration rates of sub-layers (15-30 cm) in shrub profiles was 8.11 mm/min, which was much higher than that of dry land (0.46 mm/min). The lowest value of stable infiltration rates in shrub soils was 4.22 mm/min that was thirty three times of dry lands (0.13 mm/min). Obstacle layers associated with low infiltration rates existed in sub-layers of dry land profiles. There were significant positive correlations between permeability and organic matter, soil porosity and water-stable aggregates. Water-stable aggregates and soil organic matter were the principal influential factors which affect infiltrability in Karst slope. This research provides theoretical basis of exploring and utilizing Karst water resource, soil and water resource conservation.