Evaluation of Soil Quality and Maize Growth in Different Profiles of Reclaimed Land with Coal Gangue Filling

Reclaiming subsidence and waterlogged zones caused by coal mining to maintain food and feed supplies is an urgent issue in China. Utilizing coal gangue (CG) as a filling matrix to construct different profiles of reclaimed land in coal mining subsidence has downsides, e.g., due to its low conservative capability of water-fertilizer and crop yield, its lack of quantitative evaluation of soil quality, and its limiting factors of crop growth. Quantifying the soil quality by principal component analysis (PCA), obtaining key soil indicators, and a scoring system can clarify the influence of the profile structure on soil quality and limiting productive factors of soil and ascertain the optimal profile. Soil quality was evaluated by the minimum data set (MDS) of soil quality index (SQI) obtained by PCA in seven different profiles of reclaimed plots constructed in a field with maize planting experiments. The agronomic traits of maize were analyzed and compared. The result shows that the pH value contributed highest in surface SQI value. Maximal and minimal SQI value is 0.57 and 0.18, respectively, the variation of SQI between different profiles reveals it increases with the increase in thickness of overburdens and decreases with the increase in soil interlayer depth of reclaimed land. SQI based on MDS has a correlation coefficient of 0.4280 with maize yield and the same sequence with comprehensive growth of maize in reclaimed plots. Agronomic traits of maize are positively correlated with the nutrient index and SM of the surface soil, and negatively correlated with pH, electrical conductivity (EC), and total salt content (TS). Choosing a thicker surface overburden and control pH of CG preceding filling can effectively augment soil quality and maize growth. This study provides the exploratory means and a scientific basis for the management and improvement of filling reclamation.