Preparation of topsoil alternatives for open-pit coal mines in the Hulunbuir grassland area, China

摘要

To solve topsoil shortages caused by the thinner topsoil layer resulting from open-pit land reclamation in northwestern Chinese grassland areas, the overlying rock and soil layer of an open-pit coal mine in Inner Mongolia was used as a matrix, and different additives were incorporated to improve topsoil alternatives for dump reclamation. The physical and chemical properties and nutrient composition of the undisturbed matrix and the weathering substances in layers II and III of the topsoil were compared and analyzed, with local topsoil as the control. The results showed that the III layer of the matrix after weathering had higher nutrient content, pH of 7.83, EC of 83 mu S/m, and as such was more suitable as a substitute for topsoil. Given the limitations of overlying strata, such as excessive viscosity, an imbalanced nutrient content and a lack of soil microorganisms, additives composed of vermiculite, peat, livestock manure, nitrohumic acid and microbial agents in different proportions were incorporated. Field experiments showed that the optimal formula of substitute material was a ratio of m (subclay):m (peat) = 20:1 and an applied microbial agent concentration of 0.15 kg/m(2). Compared to the original topsoil, the substitute material had a higher moisture content (32% for substitute and 20% for original topsoil), significantly higher phosphorus and potassium contents, and similar or greater numbers of microorganisms. The greatest increase in alfalfa plant height was 72%, the dry weight of the aboveground part increased by 26%.