Objective Long-term mulching increases the risk of white pollution in soil, affects soil microbial community structure, and consequently influences crop growth. This study aims to investigate the effects of long-term biodegradable mulching film coverage on soil bacterial and fungal community structures, so as to provide technical support and theoretical basis for the sustainable development of agriculture in Xinjiang.

Methods Two treatments were set up in this study: conventional plastic mulching film (CMPs) and biodegradable mulching film (BMPs). A multi-year field experiment was conducted to explore the effects of biodegradable mulching film on soil bacterial and fungal community structures in arid cotton fields.

Results The numbers of bacterial and fungal OTUs were 3,881 and 704, respectively. Among them, the numbers of unique bacterial species in the CMPs and BMPs treatments were 578 and 594, respectively, while the numbers of unique fungal species were 190 and 204, respectively. The bacterial Chao index and fungal Shannon index in the BMPs treatment were significantly higher than those in the CMPs treatment. At the phylum level, compared with the CMPs treatment, the BMPs treatment significantly increased the relative abundance of Acidobacteria and significantly decreased the relative abundance of Proteobacteria. For fungi, the BMPs treatment significantly decreased the relative abundances of Ascomycota, Mortierellomycota, and Basidiomycota. At the genus level, compared with the CMPs treatment, the BMPs treatment significantly increased the relative abundances of RB41, Arthrobacter, and Cephalotrichum, while significantly decreasing the relative abundances of Bacillus, Sphingomonas, Lophotrichus, Chaetomium, and Mortierella. The total numbers of co-occurrence network connections for soil bacteria and fungi in the BMPs treatment were 267 and 156, respectively, which were significantly higher than those in the CMPs treatment. Moreover, the BMPs treatment significantly increased the proportion of negative connections. Compared with the CMPs treatment, the BMPs treatment enhanced functions related to nitrogen metabolism and carbon metabolism, while reducing functions related to energy metabolism.

Conclusion Compared with conventional mulching film, biodegradable mulching film significantly increases the species richness and diversity of both bacteria and fungi, exhibits higher network complexity and connectivity, and enhances functions associated with nutrient cycling.