Studies On Effect Of Seasonal Grazing On Soil Quality In The Typical Steppe Region Of Abaga,Inner Mongolia

In this study,a research sample was set up in a herd pasture in Abaga,Inner Mongolia,and field surveys were carried out for spring pastures,summer pastures,autumn pastures,winter pastures and whole forbidden pastures under seasonal grazing conditions.The effects of seasonal grazing on soil physical properties and chemical properties were studied by laboratory test.At the same time,the soil quality index was screened by principal component analysis and correlation analysis,and the comprehensive index of soil quality was calculated.The results improved the understanding of the interaction between seasonal and grazing and the quality of grassland.The main conclusions are as follows:1.Based on the analysis of soil water content,bulk density and mechanical composition of pasture season,the water content of winter grassland was the highest in the 0-15 cm soil layer,and the water content of winter grassland was higher than that of summer grassland.The water content of the whole forbidden grassland did not change significantly between the surface soil and the deep soil,and its water content was moderate in the grassland.The weight of winter grassland is smaller than that of other pastures in general,with large porosity,good water permeability and high potential fertility.Indicating that the smaller the soil bulk density,the better the water holding capacity.The soil bulk density decreased gradually with the increase of soil depth in autumn,which was opposite to that of other grassland,which indicated that the compaction effect of grazing on surface soil was more significant in autumn.According to the soil texture classification standard,this study area belongs to sandy loam and sand accounted for67.69%-91.51% of the total soil particles.There was a decreasing trend in the0-15 cm soil layer with the increase of soil depth.There is a tendency to decrease gradually with the depth of soil layer in 0-15 cm soil layer.There is no obvious rule of the sticky grain with the soil layer.And the content of clay in the spring grassland is higher than that of other grassland.The more finesoil texture is formed,the more the soil aggregate structure is more complicated,which indicates that the grassland structure in spring is better than other grassland.2 According to the "second national soil grading standard",the main nutrient content of the soil in the study area is relatively low,which is below the middle level,but the influence of the different grazing season on soil chemical properties is also very significant.According to the variation range of the coefficient of variation,the coefficient of variation of available potassium in the seven soil nutrient indexes was 55.23%,which was medium variation,and the difference was 8.83 times.The coefficient of variation is16.79%,which belongs to low variation,followed by total phosphorus.The coefficient of variation is 18.53%,which indicates that the nutrient content of available phosphorus and total phosphorus is relatively stable in the soil.Based on the correlation analysis of soil chemical index,it was found that soil organic matter could effectively increase the content of soil nitrogen,phosphorus and potassium,and soil organic matter was the central index of soil nutrient.Soil comprehensive nutrient rankings are: winter pasture >spring pasture> autumn pasture > whole forbidden pasture > summer pasture.In winter,the nutrient of winter grassland was the worst and the summer grassland was the worst.In the summer season from June to August,the contents of organic matter,nitrogen and potassium were lower except for the total phosphorus and available phosphorus in the soil The Therefore,the grazing intensity of the summer grassland in the abaca flag should be reduced and the utilization of the winter and spring pastures should be appropriately strengthened.3 The factors contributing to the determination of soil quality,such as nitrogen factor,mechanical composition factor,potassium factor,bulk density factor,available phosphorus factor and pH factor,were calculated by using the principal component analysis of 13 indicators of physical chemistry.Rate can reach 85.61%.Seasonal grazing has a greater effect on soil total nitrogen and available nitrogen.Therefore,nitrogen is a more sensitive factor inseasonal rounds,and pH is less sensitive.Based on the comprehensive index of soil quality in spring pasture,summer pasture,autumn pasture,winter pasture and total forbidden grassland,the soil quality comprehensive index of five kinds of grazing pastures were: 0.717,0.600,0.629,0.777,0.567.Among them,the soil quality index of winter grassland was higher than that of spring grassland,summer grassland,autumn grassland and total forbidden grassland:8.37%,29.50%,23.53% and 37.04% respectively.The soil quality index of the summer grassland in the four seasons is the lowest,so the use of grassland should be reduced in summer,and the use of grassland can be increased in winter and spring.From the overall difference in soil quality,the annual grazing is not the best way of grazing management,seasonal enclosures for a more reasonable way of grazing management,including winter or spring grazing on the impact of soil quality is small.It is suggested that the pastoral area can expand the area of summer pastures,reduce the carrying capacity and reduce the area of winter and spring grassland.