Study On Spatial Variation Of Soil Characteristics And Evaluation Of Soil Quality In Coal Mining Subsidence Area

Coal mining forms underground goaf,which leads to surface subsidence and causes spatial variation of cultivated land soil characteristics,thus reducing soil quality.The soil characteristics can characterize the fertile and barren condition of the soil and are closely related to the growth and yield of crops.Therefore,fully grasp the spatial variation and distribution state of the soil characteristics and understand the coupling relationship between soil quality and crop growth is the basis for realizing the soil management and is also a prerequisite for land reclamation and sustainable use of soil resources in mining areas.Taking the coal mining subsidence slope of the second Coal Mine of Zhao Gu in Xinxiang City,Henan Province as the research area and based on the data sources are soil sample data collected from the field,this paper uses date source like soil sample data and wheat data which were collected from the field,using the theory of geostatistics and the method of mathematical statistics and combining with GIS space analysis technology to systematically analyze the spatial variation of soil organic matter,total nitrogen,total phosphorus,rapidly available phosphorus,moisture content,PH,saccharase and the spatial variation law and influencing factors of urease;The spatial variation of soil organic matter and total nitrogen at different sampling scales was discussed and a multi-scale ensemble model of soil organic matter and total nitrogen half variance function was constructed to analyze the spatial variation of soil organic matter and total nitrogen at different sampling scales;The three-dimensional spatial variation of soil organic matter and total nitrogen is clarified,and the three-dimensional spatial variation of soil organic matter and total nitrogen are displayed intuitively;Based on principal component analysis method and comprehensive evaluation method,soil enzyme activity and soil nutrient index are used to establish soil quality evaluation index system of coal mining subsidence slope,and comprehensive evaluation of soil quality of coal mining subsidence slope is carried out to clarify the influence of coal mining subsidence on cultivated land soil quality and wheat yield to provide theoretical guidance and technical reference for soil nutrient management and implementation in mining area.The main research results are as follows:(1)Spatial variation of soil propertiesCoal mining subsidence significantly changes the spatial structural characteristics of soil properties.Studies have shown that the spatial distribution of soil organic matter,total nitrogen,total phosphorus,rapidly available phosphorus,moisture content,PH,saccharase and urease content is different in different slope and soil depth in coal mining subsidence slope and in the 0-20 cm soil layer,the spatial variation coefficient of each factor of soil characteristic is the largest,showing a downward trend from the surface layer to the lower layer.Each factor of soil characteristic has half-square structure,and the spatial variation characteristic of different soil characteristic is different.(2)Spatial variation of soil characteristics at different scalesTaking soil organic matter and total nitrogen as examples,Statistical methods were used to investigate the spatial structure and distribution of soil characteristics on different sampling scales.There are some differences in the characteristic functions of soil organic matter and total nitrogen content on different sampling scales,and the scale effect of spatial structure is obvious.The spatial variation characteristics and the main influencing factors of soil organic matter and total nitrogen in different scales were investigated by geostatistical scale ensemble method and a multi-scale ensemble model of soil organic matter and total nitrogen was constructed.The spatial distribution of soil organic matter and total nitrogen content fitted by kriging interpolation method is basically consistent with the spatial distribution of soil organic matter and total nitrogen content fitted by single-scale kriging interpolation method.(3)Three-dimensional spatial variation of soil propertiesTaking soil organic matter and total nitrogen as examples,3D kriging interpolation method and 3D random simulation method were used respectively to perform the 3D spatial simulation of soil organic matter(0-60 cm)depth in coal mining subsidence slope and the 3D spatial distribution of soil organic matter is better reflected.The results show that the prediction accuracy of 3D stochastic simulation method is higher than that of 3D Kriging method.The spatial variation of total nitrogen in horizontal direction and vertical direction were studied by using Markov chain model and the characteristic parameters of the Markov chain model quantitatively describe the spatial distribution and transfer law of total nitrogen content in soil.The 3D Markov chain model shows the three-dimensional profile configuration of total nitrogen in coal mining subsidence slope,reflecting the correlation between different nitrogen content and its spatial distribution asymmetry and continuity.(4)Comprehensive evaluation of soil quality in coal mining subsidence slopeThe soil quality of cultivated land is obviously reduced by coal mining subsidence,and the soil quality of different subsidence slope and soil depth is different.In 0-20 cm soil layer,compared with the contrast area,the soil quality index of middle slope is lower,the soil quality index of upper slope is higher.In 20-40 cm soil layer and 40-60 cm soil layer,the soil quality index of down slope is lower and the soil quality index of middle slope is higher than that of the contrast area.The distribution of soil quality index of different soil depths is as follows: contrast area>the 0-20 cm soil layer>the 20-40 cm soil layer>the 40-60 cm soil layer.The yield characters of wheat showed different subsidence slope as follows : middle slope<down slope<upper slope<contrast area.By analyzing the relation between the soil quality and the yield in coal mining subsidence slope,the results show that there is a high correlation between wheat yield and soil quality index of upper,middle and down slopes.This study shows that the evaluation index system adopted in this paper is feasible.