Study On Soil Erosion Characteristics Under The Disturbance Of Ridge Cultivated Direction Of Black Soil Region In Bin Country

With the long-term over-cultivating and continuous cropping in the northeast black-soil region of China,it has been a severe problem that the erosion gullies cut up the rich cultivated land surface,the quality declined,nutrient flow loss and other issues highlighted.On the basis of fully understanding the temporal and spatial changes of cultivated land use structure and the characteristics of cultivated land erosion,comprehensive natural condition difference,erosion degree difference and tillage pattern difference,this research takes two towns in Bin County of Heilongjiang province as the typical areas to explore the characteristics of soil erosion under the ridge disturbance.First,The spatial distribution and the coupling laws between gully erosion of different ridges direction cultivated land and terrain in regional scale were studied based on the GIS and RS technology,integrated ridge,erosion gully,DEM data,used global spatial autocorrelation,sample of grid and so on.Second,statistical models was used to explore the effects of gully erosion on soil organic matter(SOM),total nitrogen(TN),total phosphorus(TP)and available potassium(AK),to explore the effects of gully erosion under different directions of tillage ridge on the four nutrients.Thesis research,the horizontal ridge means the direction of the crop ridge with the direction of the plot is vertical;the askew ridge means the direction of the crop ridge with the direction of the plot is horizontal.The results showed that:(1)In 1986~2000 year,the cultivated land changes in Bin Country were distributed in flat areas 2~4 degrees,in 2000~2015 year,the increase of new cultivated land has increased in high gradient.The cultivated land changes in 1986~2000 year were distributed in the low fluctuation zone,in 2000~2015 year,the increase of new land and return cultivated land has increased in high gradient;(2)In 1986~2015 year,fragmentation index was increase in 11 towns of Bin Country’s 17 towns,the overall cultivated land appeared fragmentation.The distribution of gully erosion on stable cultivated was extensive,and the density of gully erosion was relatively low compared with dynamic cultivated.The existence of erosion gully resulted of long-term effect of topography,rainfall and tillage ditch,tillage ridge was a long-term potential human erosion factor.(3)The spatial agglomeration of gully erosion was not the same in different towns,erosion degree of the dominant ridge in cultivated land was the most serious.The distribution of ridge incultivated land showed an obvious spatial auto-correlation,the different spatial distribution of ridge was the feedback toward the terrain conditions,and the reasonable spatial distribution of ridge would play a role in reducing gully density.(4)The gully density of different ridges direction in cultivated land increased first and then decreased with the elevation rising in addition to askew ridge of Tangfang town.The regularity of optimal ridge in different elevation levels was not obvious in Tangfang town,askew ridge tillage in any elevation level was optimal in Sanbao town.The interaction between slope length and slope gradient was significant.It showed that the horizontal ridge tillage was optimal under the condition of ‘small slope gradient’+‘small slope length’ or ‘big slope gradient’+‘small slope length’,and the askew ridge tillage was optimal under the condition of ‘small slope gradient’+‘big slope length’ or ‘big slope gradient’+‘big slope length’ in both towns.In 0~25 m terrain condition,askew ridge and dip ridge were the best way in Tangfang town and Sanbao town.From the view of the amount of cultivated erosion,askew ridge tillage had more effect on water and soil conservation in rolling hills region of black soil area.(5)Gully erosion had a great influence on soil nutrient contents,compared with non-gully erosion area,SOM and TN in gully erosion area decreased by 33.43% and 46.67%,respectively,but the changes of AK and TP were not obvious.Straw mulching could effectively reduce the loss of soil nutrients in gully erosion area.Gully erosion also weakened the correlation between SOM and TN.(6)SOM and TN were non-gully erosion region> dip ridge >horizontal ridge in two towns,dip ridge tillage was better than horizontal ridge in maintaining fertility in gully area.