Study On Soil & Water And N & P Losses And Control Technology In Bench-terrace Area Of Dianchi Watershed

As the agricultural non-point source (NPS) pollution has become an important factor in the water environmental deterioration and lake eutrophication in China, more and more researchers focused on the pollution mechanism and control measures of NPS. Nowadays the researches for soil-water and nutrient losses have started to be done world-widely, most of which are based on a single method of measure, demonstrating something further according to a single rainfall and a single factor, and belonging to the multi-slope study. Those are hardly done from point of view of the ecological system, and with the comprehensive method and to study the annual change of nitrogen (N) and phosphorus (P) loss on small watershed. At present, there are little reports on the research for soil and N. and P. losses in the bench-terrace area of Dianchi watershed, hence the dissertation deals with them. Two research areas selected are the small watersheds in Dayu and Songhuapu located in southeast Dianchi, Chenggong county. The concrete study includes: to montior the loss of soil and N. and P. and its process via runoff plots and catchments in water colected to search for the change features of soil erosion under the seasonal rainfall, to predict the soil erosion in small watershed by using Universal Soil Loss Equation(USLE), to analysis the change of soil and N. and P. loss by measuring the runoff as well as the change N. and P. loss in rainfall with the time and the intensity of rainfall. The dissertation tends to find the better way to control the soil-water and N. and P. loss in the terrace area in Dianchi watershed, improving the soil quality, and even to provide the rational suggestions for the ecological restoration, planning and efficent land use. The major conclusion are as follows:1.Annual rainfall is mainly predominated in May through October in the experimental area, which is 80 percent of one year. And 90 per cent of the erosivity of rainfall is in this period, especially the rainfall in June through August is 54 percent of the year. In three months, the erosivity of rainfall is 71 percent of the whole year. Therefore, these months are very important for us to control soil loss.2.The research area is classified into diferent types, including the sloping cultivated land, the sloping wilderness, the area combined the agriculture with fruit trees, orchard of Chinese chestnut. The amount of soil erosion among them is degressive in sequence. However, as for the annual loss amount of N. and P., the area combined the agriculture with fruit trees ranks first in them, orchard of Chinese chestnut next, the Cultivation of land located the slope of hill then, slope of wilderness is last.