Effect of Soil Wetting Rate on Hillslope Erosion Characteristics of Cinnamon Soil under Contour Ridge Cultivation
The difference in collapse of soil aggregate among soil wetting rates and erosion types would induce variation of hillsope erosion processes.The unique erosion characteristic of a contour ridge system may change effect of soil wetting rate on erosion processes.Simulated rainfall experiment was conducted to evaluate the characteristic of runoff,sediment yielding,and soil aggregate transport under five soil wetting rates (10 mm/h,20 mm/h,30 mm/h,60 mm/h and 90 mm/h) for cinnamon soil in a contour ridge system at different stages of erosion.The result showed that runoff was increased with the increase of soil wetting rate during inter-rill stage,but no significant difference was observed among soil wetting rates at rill stage.For sediment yield,it was enhanced gradually when soil wetting rate was increasingly shifted from 10 mm/h to 90 mm/h during both inter-rill and rill stages.Compared with 10 mm/h soil wetting rate,sediment yield from 20 mm/h,30 mm/h,60 mm/h and 90 mm/h were significantly increased by 25.16％ ～ 115.51％,95.02％ ～ 144.34％,151.03％ ～ 164.49％ and 249.42％ ～ 398.91％,respectively.The variation of soil wetting rate only changed process of runoff yielding at inter-rill stage,while it altered runoff and sediment yielding processes at rill stage.The transport of micro-aggregate,which was the chief lost size,was mainly from breakdown of 2 ～ 5 mm and 0.25 ～ 0.5 mm at inter-rill and rill stages,and critical wetting rate thresholds of 20 mm/h and 10 mm/h controlled the collapse of 2 ～ 5 mm and O.25 ～ O.5 mm size,respectively.The mean weight diameter for the transport of soil aggregate at different stages from large to small was in order of rill stage,undergoing wetting stage and inter-rill stage.
soil wetting ratecontour ridge cultivationrunoff and sediment yieldingtransport of soil aggregatecinnamon soil
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