| Overlapped area of coal and crop is an important energy and food production base in China. After coal mining, it will form mining subsidence land on the surface and will reduce the soil quality. Soil quality is an inherent attribute which closely related to the reasons of soil form and the dynamic change which caused by human society activities. Soil quality also can maintain productivity, maintain ecological environment quality and promote sustained development of animals, plants and human health. Based on the known essential attribute of external soil, soil quality evaluation presents soil intrinsic attribute quantitatively, in order to know soil correctly and properly and to manage soil in scientific way. The fundamental objective of soil quality research are as follows: Exploring the change mechanism of soil quality, researching the effect which caused by the variation of soil quality on healthy development of animals and plants. Establishing soil quality evaluation index system scientifically. Providing support and reference for maintaining the soil quality and cultivating soil directly.Thus maintaining the sustainable production of agriculture. The evaluation of the impact of mining subsidence on the cultivated land soil is essentially a comprehensive analysis and evaluation, which is about the effect of mining activities on physical, chemical and biological characteristics of soil in the overlapped area of coal and crop. The comprehensive evaluation on the impact of mining subsidence on soil plays a key role in land reclamation and ecological reconstruction, which is a basic work of the reclaimed soil characteristics analysis in mining subsidence area. It could provide the basic data for the land reclamation and ecological rehabilitation of the overlapped area of coal and crop.Therefore, we choose the typical mining subsidence land area in Jiu Lishan mine as the research object, and make full use of field investigation method, combined with fixed location monitoring, indoor analysis and mathematical statistics analysis method. We analysed the influence of the mining subsidence land(slope, cracks, waters) on the main factors of soil quality. Discussed the mining subsidence land soil quality factors, environment factors, fertility health factors in different micro topography and spatial distribution of different soil depth. We built the soil quality evaluation model of mining subsidence land and evaluation model of the soil quality degradation. Analysed the the influence of soil quality on maize yield in mining subsidence land(slope, cracks, waters). They could provide theoretical basis for soil reclamation, reported loss of arable land and the sustainable production of grain in the overlapped area of coal and crop.The main conclusions of research are as follows:(1)The mining subsidence changes the soil environmental factors significantly. In the tiny terrain on mining subsidence, mining subsidence cracks reduced the soil moisture content and pH significantly. The mining subsidence(slope, waters) increased the soil moisture content and soil p H significantly. The effects of tiny terrain on mining subsidence on soil moisture content are different. The order is: subsidence waters is more than subsidence crack, which is more than subsidence slope. And which showed the same regularity in 0-20 cm soil layer, 20-40 cm soil layer, 40-60 cm soil layer. And the effect of tiny terrain on mining subsidence on soil p H also different. The order is: sinking crack is more than subsidence waters and more than subsidence slope. And which showed the same regularity in 0-20 cm soil layer, 20-40 cm soil layer, 40-60 cm soil layer. The effect of mining subsidence on the different soil moisture content soil are different, the order are as follows:0-20 cm soil layer is more than 20-40 cm soil layer and which is more than 40-60 cm soil layer. However, the mining subsidence slope and the influence of mining subsidence crack on the soil p H and its effects on soil moisture content showed the same patterns. The effect of mining subsidence waters on soil p H is showing the opposite regularity.The mining subsidence changed the soil fertility factors significantly. Different tiny terrain on mining subsidence has great difference on soil fertility factors of soil layer. The impact of mining subsidence on soil fertility is: mining subsidence crack and subsidence waters is greater than mining subsidence slope. When the surface soil from 2m to 4m within the scope of subsidence waters, the fertility of the soil increased.The mining subsidence changed the soil health factors significantly. The mining subsidence has a larger difference on the influence of different soil health factors of soil layer. The mining subsidence on the influence of different soil moisture content soil order is as follows: 0-20 cm soil layer is more than 20-40 cm soil layer and which is more than 40-60 cm soil layer. In the tiny terrain on mining subsidence, settlement cracks has the greatest effect on the activity of soil invertase and activity of soil catalase in different soil layer. The subsidence crack has the greatest influence on the activity of soil urease in the 0-20 cm soil layer and 20-40 cm soil layer, the mining subsidence waters has the greatest influence on the activity of soil urease in the 20-40 cm soil layer. However, The mining subsidence slope has the minimum influence on the activity of soil invertase, urease and catalase in different soil layer relatively.(2)The mining subsidence changes the crop’s rhizosphere microenvironment. The coal mining subsidence on crop rhizosphere soil microenvironment shows different patterns. The crop rhizosphere soil moisture content and p H were lower than that of the rhizosphere soil. The coal mining subsidence area crop rhizosphere soil moisture content, p H value and enrichment rate is also different, and lower than controls. The crop rhizosphere soil organic matter, total nitrogen, alkali solution nitrogen, total phosphorus content are higher than in the rhizosphere, the effective phosphorus content lower than the rhizosphere. The coal mining subsidence land crop rhizosphere soil organic matter, nitrogen, phosphorus enrichment rate is also different, and lower than the control. The crop rhizosphere soil invertase, urease and catalase activity are higher than in the rhizosphere soil. The coal mining subsidence land crop rhizosphere soil invertase, urease and catalase activity of root soil are different, which are lower than the control. They showes that the slope, cracks, water of the mining subsidence reduces crop rhizosphere effect. The coal mining subsidence on the slope to the slope, the lower of the crop’s rhizosphere effect; The nearer to the mining subsidence crack, the lower of the crop’s rhizosphere effect; The closer from subsidence seeper, the lower of the crop’s rhizosphere effect.(3)The mining subsidence reduced the quality of the soil in the overlapped area of coal and crop significantly. The mining subsidence has a certain difference on the cultivated land which has the influence of different layers of soil quality. From the evaluation report on the soil quality of 0-20 cm soil layer, the different tiny terrain on mining subsidence has different influence on soil quality index. The mining subsidence has greater influence on the soil quality of downslope, and has little influence on the soil quality of upslope and midslope. The soil quality of upslope, midslope and downslope is lower than comparison respectively, the percentage is: 4.08%, 6.09%, 18.50%, the degradation index is 0.181, 0.239, 0.467, respectively.The mining subsidence crack has greater influence on the soil quality within 90 cm, lower 31.14%, 21.63%, 11.08% than comparison, the the degradation index is 0.636, 0.453, 0.232 respectively. The mining subsidence crack has little influence on the soil quality beyond 90 cm, lower 1.25%, 0.31% than comparison, the degradation index is 0.027, 0.008 respectively. In micro topography of mining subsidence, mining subsidence waters has the greatest influence on soil quality, the soil quality is lower 45.66%, 15.57%, 19.02%, 18.60%, 18.18%, 16.82% than comparison, the degradation index is 0.899, 0.314, 0.381, 0.369, 0.362, 0.335 respectively.In 20-40 cm soil layer, the influence of tiny terrain on mining subsidence on soil quality also has greater difference. Mining subsidence slope has greater influence on the soil quality of downslope, and has little impact on the soil quality of upslope and midslope. The soil quality of upslope, midslope and downslope is lower than comparison respectively, the percentage is: 3.60%, 4.20%, 11.10%, the degradation index is 0.107, 0.206, 0.352 respectively.The mining subsidence crack has greater influence on the soil quality within 60 cm, lower 14.20%, 5.40% than comparison, the the degradation index is 0.495, 0.290 respectively. The mining subsidence crack has little influence on the soil quality beyond 60 cm, almost without different. The degradation index is 0.087, 0.038, 0.170 respectively. Mining subsidence waters has the greatest influence on soil quality, the soil quality is lower 33.50%, 29.10%, 27.10%, 25.20%, 18.60%, 14.40% than comparison, the degradation index is 0.926, 0.79, 0.736, 0.678, 0.513, 0.403 respectively. The soil quality index of mining subsidence waters is lower than the soil quality index of 0-20 cm soil layer, and its degradation index is significantly greater than 0-20 cm soil layer, showed the mining subsidence waters has greater influence on the soil quality of 20-40 cm soil layer.In 40-60 cm soil layer, the effect of tiny terrain on mining subsidence on the quality of the soil is different. Mining subsidence on the quality of the soil slope with 0-20 cm soil layer and 20-40 cm soil layer showed the same regularity. The soil quality of upslope, midslope and downslope is lower than comparison respectively, the percentage is: 2.27%, 7.49%, 13.24%, the degradation index is 0.046, 0.188, 0.323 respectively.The mining subsidence crack has greater influence on the soil quality within 60 cm, lower 16.55%, 9.41% than comparison, the degradation index is 0.464, 0.261 respectively.The mining subsidence crack has little influence on the soil quality beyond 60 cm, lower3.14%, 2.09%, 0.87% than comparison, the degradation index is 0.077, 0.030, 0.018 respectively. Mining subsidence waters has the greatest influence on soil quality, the soil quality is lower 52.09%, 47.56%, 44.08%, 40.42%, 37.63%, 30.66% than comparison, the degradation index is 0.941, 0.838, 0.766, 0.682, 0.629, 0.531 respectively. The soil quality index of mining subsidence waters in 40-60 cm soil layer is lower than the soil quality index of 20-40 cm soil layer, and its degradation index is significantly greater than 20-40 cm soil layer, showed the mining subsidence waters has greater influence on the soil quality of 40-60 cm soil layer.(4)The mining subsidence has significant effect on maize yield. The influence of different tiny terrain on mining subsidence has significant differences on corn yield. The coefficient of variation effects on maize yield are 17.26%, 31.36%, 20.91% respectively, which are the medium variation. They shows that mining subsidence has different influence level on corn yield. The effect of tiny terrain on mining subsidence on maize yield is different, the order is: the subsidence cracks is more than the subsidence waters which is more than subsidence slope. The distribution characteristics of maize yield in tiny terrain on mining subsidence is consistent with soil quality, in contrast to the distribution characteristics of soil degradation index. We quantitatively analyzed the relation between maize yield and soil quality on mining subsidence in overlapped area of coal and crop. Correlation analysis showed that maize yield has significant positive correlation with mining subsidence slope, mining subsidence crack and the soil quality of mining subsidence waters. High correlation between maize yield and the soil quality of mining subsidence proved that our evaluation index system and evaluation method is practical.The innovative achievements of this study are as follows:(1) Carried out a comprehensive study on the effect of mining subsidence(slope, cracks, waters) on soil quality in overlapped area of coal and crop, analysed its spatial distribution characteristics and revealed its influence rule.To study the mining subsidence influence on the crop rhizosphere microenvironment systematically. Analysising the crop rhizosphere and the differences between the rhizosphere and norhizosphere soil characteristics. Revealing the influence law of the different coal mining subsidence micro topography on the crop’s rhizosphere microenvironment and rhizosphere effect.(2) Based on the spatial distribution characteristics of soil quality on mining subsidence land in overlapped area of coal and crop, established the evaluation model of soil quality and soil quality degradation. Studied the influence mechanism of the effect of mining subsidence on soil quality and the degradation mechanism of soil quality.Clarified the comprehensive effects of mining subsidence on soil quality in overlapped area of coal and crop, further analysed the effect of soil quality on maize yield, determined the reduction range which caused by mining subsidence, provided theoretical foundation to the breakage of mining farmland and the compensation of farmland damage. |
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