Effects Of Different Protective Types On The Prevention And Control Of Farming Soil Wind Erosion In The Loess Plateau

Soil wind erosion and desertification are important environmental problems, which affect the survival and development of human society. And sand movement caused by soil wind erosion is one of the main manifestations of sandy desertification.Farmlands in the Loess Plateau soil wind erosion area, shelter and resumed forests or grasslands from farmlands were used as the research object, fixed-point field tests, located observation and laboratory were adopted as analysis methods, PC-3 multi-channel portable automatic weather station and gradient sand dust collection device were used to observe different vegetation model farmland. The main research contents were as follows:(1) The strong winds and sandstorms spatial and temporal distribution characteristics: According to the weather data, analyzed the trends of the occurrence and development of wind erosion, established the spatial and temporal distribution characteristics of the occurrence days of strong winds and sandstorms that caused wind erosion, provided theoretical basis for the design and layout of soil wind erosion prevention and control measures.(2) The soil wind erosion prevention and control effect of conservation tillage: According to the crop growing season, growing season prevention and control and slack farming season prevention and control were divided. In the crop growing season, before and after planting and early growth period were the peak period of wind erosion, different tillage measures were used to change the surface condition, increased surface roughness and coverage, improved the soil surface moisture, enhanced the cohesion between soil particles, and enhanced the critical friction speed to prevent the occurrence of wind erosion, at the same time reviewed the growth status and yield of crop. In the slack farming season, the effect on the near-surface wind and soil wind erosion sediment migration were analyzed through the comparative experiment between different mulching methods and stubble height, and studies on wind prevention and sand resistance were carried out.(3) The wind farm effect of shelter belt (net): Different shelter belts (net) were chose to reduce wind speed, investigated shelterbelt structure and the effect of windbreak in arid and semi-arid areas, the effects of transparence degree, ventilate coefficient, belt width, tree height, forest belt trend and other factors on the wind speed movement changes were quantitative analyzed.(4) The soil wind erosion prevention and control effect of plantation grass vegetation: In the same weather and site condition, microclimate, soil texture and moisture, coverage, surface roughness and amount of wind erosion of different types of artificial vegetation were mensurated, different surface wind field coverage, roughness, wind speed, sand dust, wind attenuation and so on were studied.The conclusions showed that:(1) The occurrence frequency of strong winds showed an upward trend before 1990 and then declined, while the occurrence frequency of dust storms increased year after year, the occurrence intensity gradually increased also. From the occurrence season, strong winds and dust storms mainly occurred in the spring, and sporadic occurrence in the summer in the northern of Shaanxi Province.(2) Wind-induced movement of dust particles was effectively reduced by different tillage measures, the amount of wind erosion of ridging the land and covering membrane patterns was 28.32% lower than the conventional tillage, and the production increased 27.28%; The wind speed was reduced by coverage measures in wilderness, at 50cm height the wind speed of corn straw mulch test B reduced 30.69% ~ 31.36% than bare land; The amount of swind erosion was significantly reduced by stubble, reduced 57.38% than conventional tillage, reduced 47.58 % than nor-stubble, 40cm was the best stubble height.(3) The wind effects of sparse forest structure could up to 34.27%, the average was 32.69%, and when the transparence degree had differences between forest canopy and trunk layer the wind effect was better; The narrow belt windbreak (belt width≤5H) was better than the width belt windbreak (belt width> 5H); The wind effect enhanced with the belt height increased; The wind speed reduced by 30% effective protection distance increased with the angle value of sinusoidal between wind direction and belt increased; When the airflow entering into the forest net region, the first four forest belts before showed weakened trend, the reduction of the first belt was largest, after the first four forest belts the wind speed began to recover.(4) Different models of artificial vegetation could increase surface coverage, reduce the near-surface wind speed, and effectively reduce the handling capacity of wind flow. Mixed forest vegetation was the best model, and its coverage was more than 75% in leaf stage, and more than 30% in non-leaf stage. The roots mixed with the soil, so the soil anti-erodibility enhanced, and the wind weakened, and the occurrence of wind erosion reduced.In conclusion, ridging, covering and film mulching, shelter, plantation grass vegetation can prevent and control the occurrence of soil wind erosion, and crop conditions and yield directly affected the economic benefits of local farmers. And studying on the anti-corrosion and yield mechanism in the Loess Plateau, has an important practical and theoretical significance of the ecological environment and conditions of crop production improvement, the conservation tillage promotion and developement, the shelterbelt structure technology configuration and creation, as well as the model selection of returning farmland to forest.