Soil Erodibility Parameters Of Long Slopes Under Composite Erosion In The Black Soil Region Of Northeast China

Farmlands on long gentle slopes of black soil in Northeast China is the main source of soil erosion.Soil erodibility is an important factor affecting soil erosion.The soil erosion process in the black soil region of Northeast China is characterized by overlapping and/or coupling of wind-hydraulic-gravity-freeze-thaw,multiple in force and in process.In spring,freezing and thawing accompanies melting water,and temperature fluctuation and freezing and thawing are the dominant factors affecting soil properties,while in summer and autumn,water erosion is the main form of erosion and rainfall runoff and dry-wet alteration are the two leading factors.However,so far little has been reported in the literature about field experiments on soil erosion resistance in the black soil region under the multi-forced compound erosion,thus making it hard to effectively implement the task of controlling the multi-forced compound erosion.Taking the typical long sloping farmland of Keshan Farm in Heilongjiang Province as the research object,select a typical long sloping farmland with a length of 1400 m.The soil shear forces of undisturbed soils were determined in April and September 2018,respectively.At the same time,the water-stabilized agglomerates were determined by slow-wet treatment in Le Bissonnais method to calculate the average mass diameter(MWD)and geometry of soil aggregates.Mean diameter(GMD)and mass fractal dimension(D),and determination of organic matter content,bulk density,total porosity,capillary porosity,137 Cs area activity and calculation of soil erosion,analysis of soil erosion in long sloping farmland in black soil area Sexual parameter characteristics.The results show that:(1)Through the determination of water-stable aggregates and soil shear forces in the spring and autumn of the long-slope slopes in the black soil region,it is found that the variation range of >0.2 mm water-stable aggregates in spring is 64.94%-99.08%.The variation range between 94.90% and 99.47% in autumn;the overall MWD and GMD values in autumn are 1.27 times and 1.37 times that of spring respectively;the fractal dimension of spring soil aggregates is between 1.6875 and 2.6022,and in autumn.Between 1.4833 and 2.1418;the soil shear stress is generally greater than the spring.As the depth of the soil increases,the soil shear resistance value and the stability of the water-stable agglomerate also increase.It is indicated that the soil corrosion resistance of the long slope slope in the black soil area is better than that of the spring soil,and the soil corrosion resistance increases with the increase of the section depth.In the spring,the main erosion and erosion of the camping force has a greater impact on soil erodibility than that in autumn.(2)Soil organic matter,total porosity and capillary porosity are higher in autumn than in spring,while bulk density is higher in spring than in autumn.The same slope is in the same soil layer at different seasons(spring and autumn).There is no significant difference by LSD test..The organic matter content and bulk density increased with the increase of soil depth;the total porosity and capillary porosity decreased with the increase of soil depth.(3)By measuring the activity of soil 137 Cs on the slopes in the black soil area,the annual average erosion modulus of the black soil in the study area is 3315.64 t·km-2·a-1.The moderate slope arable land is moderately erosive.By measuring the activity of 137 Cs in the soil,it can be seen that there is an erosion oscillation period of about 150 m in the long sloping farmland in the black soil area,which shows that the activity of soil 137 Cs is “first decreased and then increased”;The activity of 137 Cs in the long-scale range of 1400 m slope shows the fluctuation trend of “reducing ~ increasing ~ decreasing ~ increasing",and the overall erosion intensity of the slope is characterized by slope > slope up > slope.Through the correlation between soil erosion modulus and soil physical and chemical properties,the soil water-stable agglomerate index(SWMWD,SWGMD,SWD,SW>0.2mm)and organic matter have good correlation with soil erosion modulus index.Shear force is a poor indicator of soil erodibility on black soil slopes in spring(freeze,melt and snow erosion),and autumn(rainfall erosion)soil shear force is a good indicator for evaluating soil erodibility on black soil slopes.The order of sensitivity of soil erodibility was indexed as SWD >SWGMD >SWMWD>SW>0.2mm > organic matter content > capillary porosity > shear force > bulk density > total porosity.Therefore,the application of water-stable agglomerates and organic matter evaluation of the black soil slope is more excellent.The research results will provide a scientific basis for the prevention and control of compound erosion in long sloping farmland in the black soil region of Northeast China.