京郊延庆农田保护性耕作措施对土壤风蚀的影响

Effects of conservation tillage measures on soil wind erosion in Yanqing,the suburb of Beijing

探究保护性耕作措施对京郊农田土壤风蚀的影响和防控作用等。野外采集京郊延庆地区几种典型农田(传统翻耕、玉米留茬、玉米留茬+覆盖、玉米秸秆覆盖)的原状土进行风洞模拟试验,对不同耕作措施农田土壤风蚀规律和影响因素进行研究。结果表明:试验条件下当风速不同时,各耕作措施农田地表的风速廓线主要呈对数函数规律递增。4种耕作措施空气动力学粗糙度的大小顺序为玉米留茬+覆盖>玉米秸秆覆盖>玉米留茬>传统翻耕;土壤风蚀强度规律为传统翻耕>玉米留茬>玉米秸秆覆盖>玉米留茬+覆盖。各措施在不同风速下的输沙率以指数函数规律递减,风沙流结构以跃移质为主。风蚀物主要集中在15 cm高度范围内的近地表。在相同的风速下,较之传统翻耕措施,保护性耕作措施总体上均能减少风蚀输沙率。与传统翻耕措施相比,玉米秸秆覆盖、玉米留茬+覆盖、玉米留茬这3种保护性耕作措施均可以削弱近地表风速,减少农田土壤风蚀;因此,可以通过推广使用保护性耕作措施来降低京郊乃至华北地区农田的土壤风蚀,保护土地生产力。

[Background]Yanqing is located in arid and semi-arid areas of northern China where wind erosion of farmland soil is serious.It is one of the sources of sand and dust in Beijing.The reason that there will be sandstorms and other disaster weather is that this region often has windy weather,dry climate,little precipitation and bare surface in spring and winter.Conservation tillage measures such as straw mulching and stubble can not only improve surface aerodynamic roughness,reduce near-surface wind speed and effectively weaken soil erosion,but also increase soil moisture and nutrients.Therefore,this study compared the effects of three conservation tillage measures including corn stubble,corn straw mulching,corn stubble and cover with traditional tillage measures on soil wind erosion,which can provide a basis for preventing soil wind erosion in this area.[Methods]Wind tunnel test with 5 wind speeds(8,12,16,20 and 24 m/s)were carried out on undisturbed soil of the farmland under 4 tillage measures in the study area.The aerodynamic roughness was calculated by using the Pitot tube to measure the wind speed profile of each axial wind speed.The soil wind erosion intensity was measured by weighing the undisturbed soil before and after the tests.The sand transport rate was calculated after weighing the wind erosion particles under different heights(1,4,7,10,13,16,19,22,25 and 28 cm)of different wind speed,which was collected by sand sampler.[Results]Under the test conditions,when the wind speed is different,the wind speed profile of the farmland surface of each tillage measure is mainly logarithmic function increasing.The order of the 4 tillage measures’aerodynamic roughness is:Corn stubble and cover>corn straw mulching>corn stubble>traditional tillage.The soil wind erosion intensity law is:Traditional tillage>corn stubble>corn straw mulching>corn stubble and cover.The sand transport rate of each measure at different wind speed decreases exponentially,and the wind-sand flow structure is dominated by saltation.The wind erosion particles is mainly concentrated in the near surface of the 15 cm height range.At the same wind speed,compared with the traditional tillage measures,the conservation tillage measures can generally reduce the sand transport rate of wind erosion.[Conclusions]Compared with the traditional tillage measures,corn straw mulching,corn stubble and cover,and corn stubble can not only weaken near-surface wind speed,but also reduce wind erosion in farmland.Therefore,we can promote the use of conservation tillage measures to reduce the soil wind erosion of farmland and protect the land productivity in the suburbs of Beijing and even in northern China.