Soil structural characteristics and its effect on infiltration on abandoned lands in semi-arid typical grassland areas

Soil rainfall infiltration, runoff and erosion are closely correlated with soil structure. Based on a new simulated rainfall method (run off-on-out method) and apparatus soil infiltration on abandoned slope lands of Yunwu Mountain in Guyuan of Ningxia were measured. The experiments were operated on slope farmland, 6 years, 11 years (graze 8 years and enclose 3 years) and 16 years abandoned lands under 17 mm/h, 43 mm/h, 56 mm/h rainfall intensities. Soil structural indices were determined in laboratory and evaluated the effects of soil structural characteristics on infiltration capability. Soil structural stability indices, pore indices and fractal indices indicated that as the years of abandoned lands increased, soil aggregate stability and porosity were significantly increased. With increasing simulated rainfall intensity, soil infiltration rates under abandoned lands increased while decreased under slope farmland. Top layer of 11 years abandoned land tightened by grazing had poor infiltration capability. By step-regression analysis soil steady infiltration rates under 17 mm/h and 56 mm/h rain intensities were mainly effected by bulk density and soil organic carbon content, and by capillary porosity under 43 mm/h rain intensity. Overall, the results indicated that soil structural characteristics controlled by soil organic carbon contents and pore characteristics largely influenced soil infiltration capability and processes.