The Effect Of Planting Soybean On Soil Erosion Resistance On Loess Plateau

The Loess Plateau has vast land and is rich in natural resources.However,most of the land is in the form of sloping land.Due to the unreasonable land use and natural factors,the water and soil loss of the Loess Plateau is serious,which can not only cause land degradation and reduce land productivity,but also cause agricultural non-point source pollution.Soil and water loss has become the main form of agricultural non-point source pollution.As the point source pollution has been controlled effectively,the problems,such as the water environmental degradation,caused by agricultural non-point source pollution become more and more important.The serious soil and water loss of Loess Plateau has become a factor which seriously restrict the healthy development of economic,social and ecological environment.Soil erosion of sloping farmland is the main source in Loess Plateau,which has become the working emphasis in the control of soil erosion in China.Agricultural production is an important part of the local economy and sloping farmland agricultural production is the main form of local agricultural production in the Loess Plateau area.Soil erosion resistance is one of the most important factors to affect soil erosion.It will be conducive to further the mechanism of soil erosion controlling studies of crops and will provide a solid theoretical basis for the agricultural production guiding to research the mechanism of crops roots on soil erosion resistance increasing.In this study,a series of experiments was designed based on artificial simulation of rainfall and soil erosion resistance determination to study the characters of runoff and sediment yield and soil erosion resistance,which include soil anti-erodibility,soil anti-scouring ability and soil shear strength,of sloping farmland under the condition of soybean planting.The main conclusions is as follows.1.The soil disintegration rate showed a decreasing trend and then increased after the initial grain forming stage,in which period the soil disintegration rate reached the minimum.And the soil anti-erodibility showed an increasing trend and then decreased after the initial grain forming stage,in which period the soil anti-erodibility reached the maximum.The enhancement rate of soil anti-erodibility by soybean root system can be up to 73%.In vertical direction,the soil disintegration rate showed an uncertain difference relative to growth stage of the crop.After blooming stage,the soil disintegration rates of 5-10 cm soil layer were lower than the other two layers,which was to say soil anti-erodibility is best in this soil layer after blooming stage.2.It will improve soil anti-scouring ability significantly if there are soybean roots in the soil.The soil anti-scouring showed an increasing trend and then decreased after the initial grain forming stage,in which period the soil anti-scouring ability reached the maximum.In vertical direction,the soil anti-scouring ability of 0-5 cm soil layer were higher than the other two layers in the seedling stage and branching stage of soybean.However,the soil anti-scouring ability of 5-10 cm soil layer were higher than the other two layers after blooming stage.The enhancement value of soil anti-scouring ability by soybean root system can be up to 6.51 min·g-1.3.The strengthening effect of soybean root system on soil shear strength was obvious.But it was different of the enhancement effect of different soil layers in various growth stages.In the same soil layer,the soil shear strength showed an increasing trend and then decreased after the initial grain forming stage,in which period the soil shear strength reached the maximum.In the same growth stage,soil shear strength showed an increasing trend with the depth of the soil.The enhancement rate of soil shear strength by soybean root system can be up to 58.15%.4.After the correlation analysis of each index of soil erosion resistance ability and the soybean root system parameter respectively,the results showed that soil erosion resistance ability is closely related to the root parameters in soil,of which,root weight,root volume and root surface area could affect soil erosion resistance ability significantly.It was highly significant correlation between soil erosion resistance ability and the root length,the root diameter of which is less than 0.05 mm.some rational agronomic management measures,use of cultivars that tend to have developed root systems,could also be adopted to improve soil erosion resistance of soybean fields.5.Under the condition of artificial rainfall simulation,the existence of the soybean plant could extend contributing time,reduce runoff velocity and runoff yield of slope surface and erosion modulus effectively.Compared with the bare land treatment,the runoff yield of slope surface was reduced by 34.21%-58.16% and the sediment production was reduced by 73.86%-80.28% in the slope,in which,there were whole plants.The effect on decreasing sediment production and runoff yield of soybean root system was between bare land treatment and whole plants treatment.Compared with the bare land treatment,the runoff yield of slope surface was reduced by 9.70%-14.78% and the sediment production was reduced by 38.35%-64.92% in the slope,in which,there were only soybean roots.The slope protection effect of soybean root mainly embodies in reducing sediment content and erosion modulus.6.Soil erosion resistance varies with the crop growing and depth in soil profile.It is quite low at the seedling and branching stages.It is,therefore,recommended that measures be taken to strengthen soil erosion resistance in the early growth period of the crop.Meanwhile,some rational agronomic management measures,like mulching,could also be adopted to improve soil erosion resistance of soybean fields.