| The purple hilly area is located in the upper reaches of the ChangJiang River, east of the Three Gorges reservoir area which is the major grain producing areas of the Sichuan Basin, its relatively large amount of chemical fertilizer, heavy precipitation and concentrated, serious soil erosion, farmland, farmland nutrient emissions gives great pressure on the environment. Purple soil layer is shallow, light soil texture, shallow soil development, poor structure, low soil water-retention capacity, soil saturated leakage rate (up to23mm/min.),Soil infiltration of water and low water holding capacity, underlain by weakly permeable parent material-the parent rock, showing the overlying soil, underlying rock "the geotechnical dual structure, the structure of the soil profile can easily make the rain fills the infiltration to the formation of subsurface flow, in the total runoff a considerable share, provided the conditions for the leaching of soil nutrients at the same time, the poor purple soil underlying surface (parent rock) permeable, so that a large part of soil seepage and reverse osmosis to face surface water pollution caused by in recent years for purple Soil surface erosion and sediment yield and nutrient migration law, many scholars have done some research, these studies generally against the slope surface runoff under the action of erosion and sediment yield, nutrient commence with the surface runoff and sediment migration of but some only study of soil runoff leaching of N. P, an element, some research methods in the absence of crop conditions, not fully understanding the purple soil nutrient loss pathway and influencing factors of production on a large area of application of straw mulch plastic film mulching, and other measures less impact study on the nutrient loss. Therefore, the soil nutrient leaching and surface runoff combined system to explore straw mulch, plastic film mulching, and other measures in the different tillage conditions on soil erosion, surface runoff and the proportion of soil runoff, soil nutrient loss, loss of channels and soil nutrient loss of the carrier, not only the needs of the theoretical development of non-point source pollution, point source pollution control needs, such research is not only necessary, but also the form of urgency.This paper clarifies the effects of tillage, cover and other measures of Purple Soil nutrient loss, by analysis and monitoring runoff plots under natural rainfall conditions, surface runoff, underground runoff, sediment loss, and its different forms of N, P and K concentration, which reveals the nutrient loss of the pathway and the loss mechanism, screening farming measures and coverage measures which control point source pollution in Slope Land, the purple Soil Erosion and farmland non-point source pollution control, provide a theoretical basis to maintain and improve soil fertility. Studies have shown that:1.Different coverage approach is superior to control runoff and erosion of sediment effect than different farming methods to deal with.Under uncovered circumstances surface runoff depth is2.7～4.8times of the subsurface flow. Compared with ridged up down, flat, ridged contour and ploughed in contour strips can reduce surface runoff depth and the total runoff deep. Flat took little obvious on reducing the amount of sediment erosion. Ridged contours and ploughed in contour strips can be more than40%reduction of sediment erosion. Dealt with accordingly and uncovered, straw mulch and the mulch cover can reduce the total runoff deep, straw mulch is better than plastic film mulching. For all processing flat+straw runoff deep minimum. Straw mulch and plastic film mulching can reduce erosion, sediment yield, straw mulch is better than plastic film mulching, erosion of ridged contour+straw is smallest and flat+straw followed in all treatments.2. The impact of tillage methods on runoff nutrient concentrations performance showed that: Compared to the ridged contour and cross sub-surface, smooth ridge increased the content of nitrogen, TP and potassium in runoff, but reduced the concentration of nitrogen in soil runoff. Flat against the runoff nutrient concentration has little effect. Farming methods have little effect on P and K concentration of soil runoff. The impact of nutrient loss of farming methods showed that, ridged contour, cross points can reduce the loss amount of nitrogen and flat increase that in runoff compared with the smooth ridge; flat, ridged contour and ploughed in contour strips also could decrease the loss amount of phosphorus in surface runoff and total runoff; ridged contour and flat could decrease the amount of TK in runoff, but ploughed in contour strips increased. The total loss amount of nutrient was substantially higher than the effective nutrient loss amount in sediment. Flat, ridged contour and ploughed in contour strips could reduce the total and effective nutrient loss.3. The effect on runoff nutrient concentrations of different coverage modes showed that:Compared with uncovered, straw mulch and the mulch cover could reduce the concentration of TN and TK in subsurface flow and TP in surface flow, but both increase the concentration of TK in surface flow. The effect on nutrient loss in runoff and sediment of different coverage modes showed that:Compared with uncovered, the other coverage treatments could reduce the amount of nitrogen loss in runoff expect ridged up down+straw; both straw and plastic film could reduce the amount of phosphorus and potassium loss in runoff, and straw treatments showed better than plastic films, flat+straw performed best which reduce the nutrient loss amount most. The result of nutrient loss in sediment showed that all coverage treatments could reduce the loss, and ridged contour+straw is lowest, flat+straw followed. Generally spoken straw treatments is better than plastic film treatments on reducing the nutrient.Compared to the traditional,down slope ridge cultivation,the contour ridge cultivation lowered nutrient.soil and water losses associated with surface and underground runoff and soil erosion.The integration of flat cultivation and straw mulching can be an improved practice as it does realize straw recycling, reduce losses of soil and water and plant nutrients. |
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