Responses of soil bacterial communities in soybean rhizosphere of abandoned mining area to fertilization methods

Objective  To evaluate the effects of chemical fertilizers combined with sodium silicate or earthworm on bacterial community in soybean rhizosphere of abandoned mining areas from the perspectives of bacterial diversity and composition structure, and provide a theoretical basis for future mining area reclamation and ecological restoration.

Method  ‘Huachun 9’ soybean was planted in the abandoned mining area of Huangshe Village, Meizhou City, Guangdong, China. Four fertilization treatments were set up. Nitrogen (N), phosphorus (P) and potassium (K) fertilizers were combined with sodium silicate (3NPK+S and 5NPK+S), NPK fertilizers were combined with 20 earthworms per square metre (3NPK+E and 5NPK+E), and No fertilizer was used as control (3CK and 5CK). Soybean rhizosphere soil was sampled three and five months after fertilizing respectively. The soil bacterial total DNA was extracted, 16S rRNA was sequenced and basic soil chemical properties were determined to analyze diversity and structure of bacterial community in soybean rhizosphere responsing to different fertilization treatments in the mining area.

Result  Compared with 3CK, 3NPK+E treatment significantly increased Chao1 and Shannon indexes. Compared with 5NPK+E, 5NPK+S treatment significantly increased Shannon index. The principal coordinate analysis (PCoA) showed that rhizosphere bacterial communities in different treatments were significantly separated at operational taxonomic unit (OTU) level. In terms of relative abundance, uncultured_f_Anaerolineaceae was the dominant genus in soil treated by 3NPK+S, 3NPK+E, 5NPK+S, and 5NPK+E. Mantel test and canonical correlation analysis (CCA) showed that soil organic matter, available phosphorus and total carbon contents had significant effects on rhizosphere bacterial community of 5NPK+E treatment.

Conclusion  The applications of NPK+S and NPK+E fertilizers can effectively improve bacterial diversity, and indirectly promote soil amendment. The bacterial communities are significantly affected by different fertilization treatments. The longer the fertilization duration was, the more significant the effect was. Uncultured_f_Anaerolineaceae is enriched in fertilized soil. It may play an important role in promoting carbon transformation and has the potential to repair soil pollution. NPK+E fertilizer increases organic matter content and promotes growth of bacterial community.