Spatial Variance Of Agricultural Soil Quality And Its Influencing Factors In The Loess Hilly-gully Regions

Soil is the material basis of human agricultural production.The quality of agricultural soil directly affects the productivity and production safety of land,and then affects human health and social economic development.Loess Hills Gully as one of the typical ecologically fragile areas,ecological sustainable development caused great concern of scholars.Therefore,exploring the spatial distribution of soil quality and its influencing factors in this area has important theoretical and practical significance for guiding decision of farmers to use land and promoting sustainable development of agriculture.In this paper,90 soil samples were obtained from Gaoqu Township,Mizhi County,Shaanxi Province,in the Loess Hilly-Gully Region based on different topographic conditions and planting methods.The soil quality was evaluated,combining the physical and chemical properties of the soil with soil heavy metals.Spatial mapping of soil quality was performed through GIS spatial analysis and geostatistical methods.And the micro and macro factors affecting soil quality were discussed.Among them,the effects and interactions of topographical factors and planting factors on soil quality is analyzed quantitatively from a microscopic perspective by combining geographic detectors and redundant analysis methods.Simultaneously,based on the landscape pattern index,the coupling relationship between landscape pattern and soil quality is explored from a macro perspective through redundant analysis.Finally,suggestions for sustainable development of agriculture were put forward based.The results are as follows:(1)Comprehensive evaluation of soil quality.The agricultural soil fertility in the study area is in grades IV(53.33%)and V(46.67%).Low organic matter and total nitrogen content,and alkaline p H have become the main factors limiting soil fertility.Soil heavy metals is at a clean level.There are two levels of comprehensive ecological risk levels: mild risk level(16.7%)and medium risk level(83.3%).The comprehensive soil quality is in grades III(5.56%),IV(77.78%),and V(16.67%).(2)Spatial distribution characteristics of soil quality.The spatial correlations of soil organic matter,total nitrogen,alkaline nitrogen,and available phosphorus in the study area are strong.Spatial correlations of total phosphorus and p H are moderate.Soil nutrient elements appear locally as “lumpy” high-value areas.The spatial change of p H is mainly from the southeast to the northwest.Soil fertility is higher in the west and lower in the east.Spatial correlation of the Pb and Zn are strong,and that of the As,Cu,Cr,and Ni elements are moderate.The spatial distribution of heavy metal elements is complex,with local high and low values.Pollution levels of soil heavy metal is lower in the north and south area than middle area.The spatial distribution of soil comprehensive quality and soil fertility quality are similar.(3)The analysis of influencing factors shows that: from a micro perspective,the impact of topography on soil quality is greater than that of planting factors of plots on soil quality.The major factors that affect the soil fertility quality and soil comprehensive quality are slope direction and plot area.The main factors affecting soil environmental quality are the slope direction and the distance of the plot from the road.The interaction of the two factors is greater than the effect of the single factor on soil quality.From a macro perspective,landscape pattern has some influence on soil quality.Among them,the percentage of forest land in the landscape and the complexity of the landscape shape have a significant impact.(4)Suggestions and measures for sustainable agricultural development.Improve the alkaline environment of the soil through scientific rationalization of agricultural inputs,implementation of rotation planting systems,and optimization of tree species.Reduce soil erosion by improving terrace facilities and developing industries of forestry and fruit.Improve farmers' scientific management capabilities and cultivate risk prevention awareness of them.Take advantage of terrain and arrange planting reasonably.Set up grassland buffer zones to prevent the potential harm of heavy metals.Optimize the landscape pattern rationally,and retain water and fertilizer of soil.