Study On Environment Effect Of The Level Terrace In Southern Of Loess Plateau

Level terrace is one of the methods of preventing and cure soil erosion, which is the local masses and the masses of scientists during practice of struggling against soil erosion .In process of production, level terrace can conserve water, soil and maintenance nutrient, and raise land productivity. At the same time, it unavoidably cause moisture lose and soil pollution. The systematically study on the environment effect of level terrace, among the ecological environment construction in the development of the West Regions, is the key to resuming and rebuilding the ecological environment in loess plateau by. On the basis of studied results, the paper systematically studied and probed on the environment effect of level terrace through field survey, indoor experiment and summarizing data as well as analysis under guiding soil erosion, soil science and environmental pedology in the south part of Loess Plateau. Expected that can build and make certain contribution for the construction of ecological agriculture.1 .This text made PI as main factors, and analysis the runoff and sediment reducing benefit of level terrace. At PI < 20.0mm2/min, level terrace accomplish conservation, its benefit was 100%; as well as PI > 20.0 mm2/min,the benefits would reduce with increased of PL2.With annual rainfall output and flood season rainfall as annual rainfall index, we found the benefit would reduce with the increases of rainfall when the annual rainfall was greater than 350 mm or the flood reason rainfall was larger than 125 mm.3.Through analyzing the distribution of soil moisture in different land, we found level terrace have obvious conservation because of dispelling precipitation reallocate condition and the moistures at the profile distribute more rational. The variations coefficient of moisture storage in level terrace were lower 2.89 percentage than sloping field in 2 meter depth of soil layers.4.The soil nutrient losses were connected with soil texture, water content and fertilizer quantity, and lands utilize way. By artificial rainfall the losses of soil nutrient were found increasing with the increasing of time or rainfall intensity in sloping field. And the relations of time and nutrient contents were extremely remarkable in runoff5.In different land utilizing, the contents and space distribution of nutrients were different. In surface layer (0-20cm) of level terrace, the contents of soil nutrients were obviously higher than the nutrient contents of sloping fields, proved that level terrace have obvious benefit of conservation nutrients. At 100-160cm depth of the level terrace layer have a NCV-N accumulation layer because of using nitrogen in a large amount for a long time. In order to develop ecological agriculture and green agriculture, wemust recommend and use in right amount, and scientific using chemical fertilizer along with the development of agricultural production.6.While level terrace had the functions of conserving soil and water storage, it increased the possibility of the soil pollution too. Because using pesticide and chemical fertilizer in a large amount for a long time in terraced orchard, level terrace was apt to accumulate harmful element, thus form the pollution to the soil, and influence the quality of crop and mankind healthy in varying degrees. At different land the profile (space), time series or slope series of use patterns, the same element content in soil demonstrated different change characteristics. Heavy metal, such as mercury, copper, magnesium, manganese and zinc among surface layer soil, their content were greater than their background value in loess soil. And the contents of nickel and chromium were smaller than background value; the average contents of arsenic were pretty to value backgrounds of. The contents of copper were already larger than the critical value (100 mg/kg) making the crop drop 10% of production...