| As the water source of middle route line of South-to-North Water Transfer Project,the water quality of Danjiangkou reservoir area is at good situation and is suitable forwater transfor in general. With development of agriculture, it is also facing more andmore serious water pollution problem which is mainly caused by agriculture NPSpollution and water and soil loss. Therefore, it is important to study agriculture NPS pollution andwater and soil loss with mainly soil in danjiangkou reservoir, and it is useful for setting up of themodel for NPS pollution.In this thesis, with simulated rainfall equipment, factors affecting soil and water lossand soil nutrients(TN,NH4-N,NO3-N,TP,AP) from purple soil, such as slope gradient,rain intensity and fertilizer measure are discussed.The main results obtained in this studyare as follows:(1) Soil erosion coused by rainfull enhances when slope gradient and rain intensityincrease. Different fertilizer measure is not interrelated with soil erosion. Compared with5°, average infiltration rates reduces 1/5 under 10°and reduce 1/2 under 20°;runoff-yielding time reduces 0.21min and 1.61min; but runoff increases 11.28％and18.62％; sediment increases 23.29％and 31.87％. When rain intensity increases from0.5mm/min to 1.0mm/min, average infiltration rates increase twice, runoff increases 1.5times and sediment increase a few, but runoff-yielding time reduce.(2) When slope gradient or rain intensity increases the content of nitrogen and phosphorus inrunoff increase. The fertilizer measure can increse the consistence and content of nutrient in runoff.Slope gradient is not interrelated with the consistence of available nutrient(NH4-N, NO3-N, AP) inrunoff, but can affect total nutrient(TN, TP).When slope gradient, the consistence of TN reduces, butTP increse. Rain intensity affects little on the consistence of nutrient. While rain intensity increases,the consistence of NO3-N and TP increase sharply, NH4-N reduce, and TN and AP change little.(3) Slope gradient, rain intensity and fertilizer measure have different effect on the loss ofnutrient in sediment. When slope gradient increase, the consistence of nutrient in sediment reduces, butthe content of nitrogen and phosphorus in sediment increases except AP. When rain intensityincreases from 0.5mm/min to 1.0mm/min, the content of NO3-N and NH4-N reduce, APincrease, TN and TP change lillle.The consistence of nutrient (NH4-N, TN,AP, TP) in sediment under1.0mm/min is largerer than 0.5 mm/min, except NO3-N. The consistence of all nutrient besides TPin sediment increase after fertilizer measure.(4) The content of nutriment after rainfall is lower than the content of nutrimentbefore rainfall in surface layer of soil except AP and NH4-N. The content of nutrients loss from the layer of soil is not interrelated with rainfall intensity and slope. After fertilizingwith nitrogenous fertilizer or phosphatic fertilizer can increase the content of nutrients inthe layer of soil and the content of nutrients loss. But if two mix fertilize can reduce thisinfluence.(5) Under natural rainfall, the influences of rainfall, slope gradient and fertilizationhave different effect on the enrichment ratio (ER) of nitrogen and phosphorus in sediment.According to the ER of N, the order of the three is NH4-N＞TN＞NO3-N.ER of AP is largerthan TP. All nutrients reduce when slope gradient(5°-20°) or rain intensity(0.5-1.0mm/min)increase.Afer fertilizing ER increases except TP, which keep the same under differentfertilizer measure.(6) The consistence of NO3-N in soil mainly losses in runoff, but NH4-N, TN, AP andTP mainly loss in sediment.(7) The sediments of eroded field richly gathered＜0.02mm clays and＜0.002mmmicroaggregates. The nutrient loss of the total nutrient is caused by＜0.02 mmmicroaggregates and the available nutrient is caused by 0.02～0.002 mm microaggregates.
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