Experiment and analysis of high water retention coal gangue reconstructed soil in the mining area of the farming-pastoral ecotone in China

Owing to the unique climatic conditions and ecologically fragile characteristics of farming-pastoral ecotone regions, soil reconstruction in mining areas must be performed with caution to ensure favorable soil moisture. In this study, to explore an appropriate method for reconstructing soil with coal gangue, a three-stage indoor soil column experiment was conducted to investigate the Soil Water Content (SWC) characteristics, vertical water distribution pattern, and water-holding capacity of reconstructed soil with different mixture ratios and thicknesses, as well as the changes in SWC before and after watering and fertilization activities. The Coal Gangue-mixed Topsoil (CGTS) 1:1 (mixing ratio) exhibited the best recovery effect (39.51 %) and the SWC in the 60-cm and 50-cm thick soil was superior to that in the 40-cm soil. The water movement in the reconstructed soil was similar to that of the control group and all the experimental groups could adapt well to watering and the application of organic fertilizer; however there were significant differences in the water-holding capacities of the various experimental groups, whereas the CGTS1:1a and CGTS2:1c groups reached the level of undamaged soil (51.78 % and 60.42 %, respectively). Accordingly this research indicates that in the farming-pastoral ecotone mining area, a 1:1 ratio of gangue to topsoil and a 60 cm thickness of the reconstructed layer can achieve good volumetric water content and water-holding capacity, providing certain references for soil reconstruction and sustainable use of mining solid waste.