Influence Of Two Cropping Patterns On Soil And Water Conservation Effects Of Dark Brown Soil With Different Slopes

Most of the dark brown soil in the black soil region is distributed on sloped farmland.Soil erosion was a serious problem,which has a great impact on grain yield and seriously hinders the sustainable development of agriculture.Therefore,this thesis selected the Xingmu Soil and Water Conservation Base in Anshi Town,Dongliao County,Jilin Province as the text area.Through three years(2013 ~ 2015)of runoff plots positioning experiment and indoor analysis,we explored the influnence of horizontal ridge rotation(corn/soybean)and cross slope grass strip(Medicago sativa)cropping patterns on soil physical property,chemical property and soil and water conservation property,revealed the spatial variability of soil physical and chemical properties of sloped farmland in dark brown soil.Based on the principal component analysis,the contribution rate of each index to the properties of dark brown soil was quantitatively analyzed,and the effects of two cropping patterns on soil and water conservation effects of dark brown soil with different slopes were comprehensively evaluated.It lays a theoretical foundation for further study on the scientific cropping model of sloped farmland dark brown soil and the improvement of soil properties and prevention of soil and water loss.It plays an important role in stabilizing the grain market and ensuring national food security.The main conclusions were as follows:(1)Soil bulk density of rotation and grass strip with different slopes was lower than that of natural slope.The content of soil total porosity,capillary porosity and > 0.25 mm water-stable aggregates in each test plot of rotation and grass strip with different slopes were higher than that in natural slope plots.Soil particles and micro-aggregates in sloped farmland of dark brown soil had higher content of large soil particles,and less content of clay particles or < 0.002 mm microaggregates.The soil fertility was low.The soil CEC concentration,organic matter,total nitrogen,available nitrogen,total phosphorus and available phosphorus were all higher than those in natural slope.(2)The rotation and grass strip have the effect of inhibiting the movement and loss of soil particles and nutrients in dark brown soil sloped farmland with different slopes.The physical and chemical properties of dark brown soil sloping farmland have spatial variability.The soil particles were mainly fine particles which migrated down the slope in the dark brown soil sloped farmland with different slopes and different cropping patterns.The phosphorus loss in the soil of each plot was mainly caused by the migration of fine powder size(0.002-0.02mm)microaggregates or < 0.002 mm single particles.(3)The best soil infiltration performance was in rotation plot with a slope of 5°,and which was the worst in natural slope with a slope of 10°.Among different cropping patterns,the infiltration performance of rotation was the best,the grass strip was the second,and the natural slope was the worst.The yield and sediment yield of rotation and grass strip were significantly lower than that of natural slope.By mechanical analysis for sediment from each text plot,the sand content in sediment from the natural slope plots were higher,and which in the sediment from the rotation plots and grass strip plots were less.The content of clay and fine silt in the sediment from the rotation plots and grass strip plots were higher.It is further shown that rotation and grass strip with these two cropping patterns have effects on preventing runoff and sediment in sloped farmland of dark brown soil.(4)Based on principal component analysis,the effects of two cropping patterns on soil and water conservation of dark brown soil with different slopes were evaluated.The results showed that rotation had the best soil and water conservation effect on dark brown soil with different slopes,followed by grass strip with different slopes.