Study On The Water Characteristics And The Infiltration Capacity Of Red-soil In The Southeast Of Hubei Province

In the red region of the southeast of Hubei province , the end of the summer and autumn are the drought season , soil water is very important for crop production and erosion at that time. My research include the water characteristics of several kinds of erosion soil using pressure membrane extractor and the percolation characteristics using simulator rainfall in the fields and in the lab.The water-holding capacity of red soil derived from Q2 was higher than the red soil derived from Granite. In the lower soil suction range , the different among the water-holding capacity of weekly and moderate and Intensely erosive red-soil derived from Q2 and Granite was not widely. In the higher soil suction range the different was widely. That of the intensely erosive red-soil was higher than the moderate and intensely erosive red-soil.The water-supply capacity of red soil in the lower soil suction range was higher than that of in the higher soil suction range. In the lower soil suction range , The water-supply capacity of red soil derived from Q2 was higher than that derived from granite while In the higher soil suction range the different was not widely. As to the different mother material, The water-supply capacity of weekly erosive red-soil was the highest that of the moderate was the secondly ,that of the intensely erosive red-soil was the lowest.Available water capacity of weekly erosion red-soil derived from Qz was higher than that derived from granite. Those of moderate and intensely erosive red-soil derived from Q2 was lower than that derived from granite. As to the same mother material , the water- validity of the weekly erosive red-soil is higher than the moderate and intensely erosive red-soil.The bulk density of aggregates increased when the size of aggregates decreased while the total porosities decreased . Some special soil water content and the aerate porosities in the low suction decreased when the size of aggregates decreased.The saturated hydraulic conductivity of the red-soil derived from Q2 was lower than that of granite. The saturated hydraulic conductivity and the water diffusion rate of the weekly erosion-soil were higher than those of the moderate and intensely erosive erosion-soils. In the lower water saturatepercentage , the difference between water diffusion rate of red-soil derived from different mother material was not widely. But in the higher water saturate percentage, the water diffusion rate of red-soil derived from Q> was lower than that of granite.In the condition of simulator rainfall ,with the time goes on , the percolation rate is gradually increase .until runoff come into being , the percolation rate reach the max .After that the percolation rate is gradually decline .when the runoff rate reach the stabilization , the percolation rate reach the stabilization, in the same rainfall condition , the different of percolation rate is widely between the different erosive degree , percolation rate of the weekly erosive soil is faster than the moderate and intensely erosive soil .The cumulative percolation have the same tendency . The water content before the rainfall , the bulk density, the site of the slope , the intensity of the rainfall and the raindrop kinetic energy would effected the percolation capacity distinctly .The total water content decrease distinctively after rain and the gravitational water content and unavailable water content decrease while available water content increase , the slow available water content have not the distinctive rule. The total porosity and the aerate porosity decrease after the rain while the faster available porosity and the slow available porosity increase .Further more the saturated hydraulic conductivity decrease highly ,and the degree of decrease of the saturated hydraulic conductivity in the bottle of the slope is more than the top.