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榆林地区总面积43578平方公里,全区12个县都是水土流失重点县,是我省土壤侵蚀模数最大、输沙量最多、洪水含沙量最高、泥沙颗粒最粗的一个水土流失严重地区。据资料分析,我区每亩坡耕地每年平均流失8吨表土,在每吨表土中,含氮量0.8~1.5公斤,磷1.5公斤,钾20公斤。全区现有坡耕地1200万亩,每年流失氮、磷、钾肥达216万吨,相当于每年化肥使用量的20倍。土壤肥份大量流失,坡耕地的亩产只有25公斤左右,严重地影响农业生产的发展。大量土壤的流失,特别是粒径大于0.05毫米以上的粗砂,使我区200多座水库,每年平均损失约4000万立方米的库容。此外,我区旱、
Yulin area with a total area of 43578 square kilometers, 12 counties in the region are key counties, is the largest in our province soil erosion modulus, sediment discharge is the most abundant, the highest sediment concentration, the most coarse sediment particles of a soil erosion area. According to the data analysis, the average loss of 8 tons of topsoil per acre of slope farmland per mu in our region is 0.8-1.5 kg nitrogen, 1.5 kg phosphorus and 20 kg potassium per tonne of topsoil. The existing slopes of 1,200 acres of arable land, annual loss of nitrogen, phosphorus and potassium reached 2.16 million tons, equivalent to 20 times the annual amount of fertilizer. Large amount of soil manure loss, slope acreage of only 25 kg per mu, seriously affecting the development of agricultural production. The loss of a large amount of soil, especially coarse sand with particle size larger than 0.05 mm, has caused more than 200 reservoirs in our district to lose an average of about 40 million cubic meters of storage capacity each year. In addition, my area drought,