Spatial distribution regularities of farmland soil quality in subsidence areas of coal filling mining and non-filling mining

Correlation research results showed that underground filling coal mining can effectively alleviate ground surface settlement in coal mining areas. To study whether filling coal mining was effective in protecting surface soils in cultivated lands, especially the ability of effectively maintaining soil fertility, an investigation was conducted in CT101 filling working face and 1013 non-filling working face in Wugou Coal Mine of Northern Anhui Mining Group. The test region and control region were set in the corresponding surfaces above the filling mining working face and non-filling working face. The two regions both non-filling area (A) and filling mine area (B) included division A₁ or B₁ in slope base of surface subsidence (point 1 to point 3 ), division A₂ or B₂ in middle subsidence slope (point 4 to point 6 ) and division A₃ or B₃ at top edge of subsidence (point 7 to point 9 ). In accordance with nine sampling points of each regions, each point was separately sampled at three soil depths 0-20 cm (H1), 20-40 cm (H2) and 40-60 cm (H3) and two parallel samples collected for each depth, totaling 108 samples in the two regions. By this way, the physical properties (including soil bulk density and water content) and nutrients (including organic matter, available nitrogen, available phosphorus and available potassium contents), the height and yield of wheat in the two regions were analyzed. The results showed that nutrients contents of surface soil in the test region were higher than those in the control region. Based on observations during the experimental period, wheat growth in zones B₂ and B₃ was better than that in zones A₂ and A₃ from May to June until harvest. However, this was not the case for wheat height in zone B₁, which was shorter than that in zone A₁ in March. Wheat yield was higher in B zones than that in A zones at harvest. Soil moisture in the test region was higher than that in the control region. The analysis showed that mine filling activity had a stronger ability than non-filling in holding nutrients and water in overlying soils in mining areas. This was critical for the protection of land and the environment. Compared with normal soil background values, however, the overlying soils of mine filling area still exhibited some problems with nutrients contents such as organic matter and available phosphorus. With regards any effect on agriculture field, mine filling areas needed strengthened artificial activities such as addition of fertilizers, strengthening of field management, etc.