Organic-inorganic combined fertilization alters reclaimed soil bacterial communities in an opencast coal mine area and improves soil quality

Opencast coal mining accelerates soil quality decline through removal of surface soil. Fertilization can influence soil biogeochemical processes by altering microbial community composition and influencing soil quality. Land impaired by mining activity can be restored to a productive state by fertilization. However, the effects of organic-inorganic fertilization on reclaimed soil biochemical features, coupled with the associated underlying microbial mechanisms, remain poorly understood, which is critical for predicting the associated soil quality. This study used high-throughput sequencing to analyze the community structure of soil bacteria in reclaimed soil from the Pingshuo opencast coal mine. We collected soil samples after the following fertilization treatments were applied: no fertilizer (CK), single applications of inorganic fertilizer (H) and organic fertilizer (S), and combined applications of inorganic and organic fertilizer at a 1:1 ratio (HS1) and a 1:1.5 ratio (HS1.5). High-throughput sequencing analyses of 16S RNA genes revealed that organic-inorganic fertilization altered the bacteria community structure. Differences were detected by cluster analysis, and the HS1 contained more abundant bacteria than other treatments by differential contribution analysis. Redundancy analyses showed that environmental properties explained most of the variation (62%) in the soil microbial community compositions. Kyoto Encyclopedia of Genes and Genomes analysis indicated enhancement of the metabolism functions and environmental adaptation of the bacterial community following HS1. Ten species of bacteria, noted for degradation of complex C compounds, were significantly ( p < 0.05) higher in HS1 compared to the rest coupled with N and P cycling-related bacteria. This led to enhanced C degradation and improved reclaimed soil quality. The improved soil also had higher total organic carbon and enzyme levels. Fertilization shifted the predominant microbial strategies and improved soil biochemical properties, accelerating soil organic matter decomposition and improving soil quality.