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各种不同利用情况的土地中,坡耕的水土流失是相当严重和至关重要的。据山西省水土保持科学研究所的观测,晋西黄土丘陵沟壑区的王家沟,坡耕地的侵蚀模数为4830～11838吨/平方公里。在全流侵蚀总量中,来自坡耕地的占百分之52.5%。以当地土壤含氮、磷、钾肥份的一般情况计算,平均每亩每年要冲走全氮2.6～4.8公斤,五氧化二磷4.8公斤,氧化钾64.4公斤,流失的氮素相当于农家肥2000～4800斤,或者64斤碳酸氢铵。磷、钾肥损失分别相当于52斤过磷酸钙、103斤硫酸钾。 由于跑水、跑土、跑肥,加之冲刷破坏了土壤结构,恶化了土壤理化性质,因而肥力大为减退,所以坡耕地的作物产量很低。将坡耕地修成田面平整并具有一定宽度的地块,就是水平梯田。能防治流失,保
Soil erosion in different types of land use is very serious and crucial. According to the observation of Shanxi Provincial Institute of Soil and Water Conservation, the erosion modulus of Wangjiagou and slope farmland in the loess hilly and gully regions in western Shanxi is 4830-11838 t / km 2. In the total erosion of the total flow, from sloping fields accounted for 52.5%. Calculated on the basis of the general situation of nitrogen, phosphorus and potassium in the local soil, the average nitrogen per mu should wash away 2.6-4.8 kg of total nitrogen, 4.8 kg of phosphorus pentoxide and 64.4 kg of potassium oxide per annum, and the lost nitrogen is equivalent to farmyard manure 2000 ~ 4800 pounds, or 64 pounds of ammonium bicarbonate. Phosphorus, potassium loss equivalent to 52 kg of superphosphate, 103 kg of potassium sulfate. Because of running water, running the soil, running fertilizer, combined with erosion destroyed the soil structure, deteriorating the physical and chemical properties of the soil, which greatly reduced fertility, so the sloping crop yield is very low. The sloping farmland into a flat surface and a certain width of the land, is the level of terraced fields. Can prevent loss, Paul