Studies On The Law Of Soil Erosion Of Watershed In The Hill Region Of Hunan Province

Soil erosion and river jam, flooding, nutrient losses, soil degradation, water pollution aroused by erosion are the key points to sustainable agricultural development in China. Soil erosion in Zhiyun village watershed in Qidong county of Hunan province during exploitation from 1993-2000 was studied. 11 runoff plots and 6 catchments were built, and runoff and soil loss were monitored. The major conclusions are as follows:1. Terrace, rotation by crop and grass and fir notably reduce slope soil loss. Terrace, fir and bamboo markedly reduce runoff and large particle in sediment transported by runoff. Rotation by crop and grass only evidently reduce large particle in sediment transported by runoff.2. Catchment 1, 2, 4 were mostly transformed from slope to terrace change since 1993, and chestnut, plum, orange, peach and bamboo were planted in 1993. Soil erosion were severe in first and second years, since then with plant cover increasing and soil consolidation, soil erosion has become steady.3. Under condition of good light and heat in South China, if there were destruction by human vegetation could restored very well. So soil erosion could be ignored. Catchment 5, 3, 6 are reservation regions with plant coverage of 9-20%, 35-55% and 70% respectively, and their average erosion modulus is 21.87, 7.47and 2.65Mg/hm2/a.4. Soil erosion in Zhiyun village watershed mainly takes place between March and September, concentrated from April to July, especially in June. This is determined by the seasonal distribution of rainfall. Also serious erosion is brought by frequent farming activities.5. Rainfall, runoff and vegetation are mainly factors impacting soil loss in red soil watershed. Rainfall erosive ability is more important than rainfall in slope soil erosion, but in watershed rainfall has more effect than rainfall in both slope and watershed.