Effects of residual mulching films with different mulching years on the diversity of soil microbial communities in typical regions

Polyethylene mulching film plays a critical role in agricultural production. To clarify the impact of residual film and microplastics on soil microorganisms, this study examined four cotton fields with different film coverage years in typical areas of Xinjiang and analyzed the changes in soil bacterial and fungal community structure and diversity under residual film and microplastics using high-throughput sequencing technology. The results showed that the residual film in the 0–150 mm soil layers and 150–300 mm soil layers at the same sampling point had spatial distribution characteristics of 60–70% and 30–40%, respectively. The short period of the 0–10 years film mulching treatment increased the soil microbial diversity of the cotton field, whereas continuous film mulching for 25 years significantly decreased the soil microbial diversity, in which Proteobacteria was the dominant bacterial phylum and Ascomycetes was the dominant fungal phylum. The microbial diversity of the film-covered soil was lower than that of the control group. The spatial distribution of the residual film and microplastic changed the distribution of the microbial communities. The diversity of the microbial community structure of the 0–150 mm soil layers was higher than that of the 150–300 mm soil layers. The increase in residual film and microplastics had no significant effect on the diversity of the fungal community but decreased the diversity of the soil bacterial community and decreased the relative abundance of Proteobacteria and Campylobacter. In conclusion, long-term film mulching reduced the soil microbial diversity in cotton fields. This study provides a theoretical basis for understanding the impact of film residues on microorganisms and the ecological environment in typical areas.