Study On Soil And Water Conservation Engineering Erosion Control Technologies Of Thin Layer Soil Slope Farmland

China is one of the most serious soil erosion countries in the world, for a long time, the research of farmland soil and water conservation engineering and covering technology is always the focus and hot spot, and has formed a series of effective technology of soil and water conservation of farmland such as transforming slope into terrace, covering, minimum tillage and no-tillage. But there is still no stable engineering technology for the governance of soil erosion in thin layer slope farmland,it is becoming the "bottleneck" of farmland soil erosion governance and it is restricting the soil and water conservation work of farmland.In view of the problems of thin soil layer, large soil erosion area, high erosion intensity and difficult governance in mountainous area and based on the huge difference of runoff form, erosion kinetic and erosion intensity between surface erosion and gully erosion, corresponding engineering erosion control technologies of thin layer soil slope farmland have been designed. Through the 3 years’ observation in field runoff plots, the control effectiveness and stability, economic feasibility, production and maintenance convenience of different design had been analyzed and evaluated, and has come out following main conclusions:(1) Terrace open and runoff storage technology of straight slope farmland had good surface runoff and sediment regulation effects, the average runoff cutting rate and erosion cutting rate reached 31.48% and 94.25% respectively. Through the regulation of runoff and sediment by terrace open and runoff storage technology of straight slope, this technology can reduce the loss of soil nutrient and increase the soil moisture content. And this can improve the productivity of slope farmland and have a certain effect on the increase of crop yield. The average annual yield of Spring Maize in experimental plot had increased by 6%. According to the cost of field runoff plot layout, the project cost of terrace open and runoff storage technology was estimated to be 1165 Yuan/Mu, only 29% of the project cost of northern Rocky Mountain Rock Ridge Terrace, and it proved that this technology has good economic applicability.(2) Gravel cutting slope and soil drainage technology of straight slope farmland had certain runoff and sediment regulation effects of slope on the initial layout stage, the runoff cutting rate and erosion cutting rate on the initial layout stage were 38.93% and 36.43% respectively. Because the gravel filter layer was easily blocked, the runoff cutting efficiency and erosion cutting efficiency decreased sharply with the increase of the age of layout of the technology, the slope water sediment regulation effect was unstable and it did not meet the design expectations.(3) The comparative analysis of the effect of two straight slope engineering technologies and supplementary analysis on the terrace open and runoff storage technology showed that terrace open and runoff storage technology had more stable erosion control effect, cleaning and maintenance convenience, both ecological and economic benefits compared with gravel cutting slope and soil drainage, parameter design of terrace open and runoff storage technology had been basically completed, and it could be applied as the main engineering corrosion control technology in straight thin soil layer slope farmland in a certain range.(4) As the experimental design of erosion control technology of thin layer soil wavy slope, retaining and filtering-drainage technology of wavy slope farmland had met the design expectations. It can basically satisfy the soil erosion prevention and control requirements of wavy slope farmland. Its annual average runoff cutting rate and erosion cutting rate were reached 48.91% and 87.01% which proved that the design idea of "retain- filtering-drainage" was basically feasible. But it still existed the problems that filter layer blocked, drainage efficiency decreased and cleaning maintenance was relative inconvenient.(5) As the optimized design of erosion control technology of thin layer soil wavy slope farmland, the design ideas of Mortar laid stone retaining and precipitating-drainage technology of wavy slope farmland “retaining-filtering-drainage” was adjusted to “retaining-precipitation-drainage”. This technology had good effects on the control of surface erosion of slope farmland, the annual average runoff cutting rate and erosion cutting rate reached 96.88% and 99.52% respectively. According to the cost of field runoff plot layout, the project cost of mortar laid stone retaining and precipitating-drainage technology was estimated to be 1887 Yuan/Mu, only 47% of the project cost of northern Rocky Mountain Rock Ridge Terrace, and it proved that this technology has good economic applicability.(6) As the simplified design of erosion control technology of thin layer soil wavy slope and based on the good application effect of mortar laid stone retaining and precipitating-drainage technology in slope sediments underlying surface, Precast slab retaining and precipitating-drainage technology of wavy slope farmland was designed. This technology had achieved good effect by set in the loess underlying surface of thin layer soil slope farmland. The runoff cutting rate and erosion cutting rate were 41.99% and 80.03% respectively. This indicated that the application of retaining and precipitating-drainage technology to loess underlying surface slope farmland was feasible. The project cost of precast slab retaining and precipitating-drainage technology was estimated to be 11387 Yuan/Mu, it was 40% less than that of mortar laid stone retaining and precipitating-drainage technology, and 75% less than that of northern Rocky Mountain Rock Ridge Terrace This technology had met the original design intention of reducing construction process and engineering cost.(7) Engineering erosion control technologies of wavy slope farmland experienced the experimental design, optimization design and simplification design stages, and the stability, underlying applicable and the control effect had been verified. Main components of this technology had achieved the factory production conditions, and the cost of it had been further reduced; the parameters of this technology had been basically completed, after the field layout, this technology needs only one cleaning by ordinary tools every year, it is convenient to maintenance, it could be applied in a certain range.