What will polyethylene film mulching bring to the root-associated microbial community of Paeonia ostii?

Plastic film mulching can increase crop yield and is widely used in agricultural production, but long-term mulching could adversely affect plant growth. To investigate the related mechanism, we studied the bacterial communities in different root-associated compartments of Paeonia ostii, a perennial oil crop, under polyethylene film mulching for three years by full-length 16S rDNA sequencing technology, and measured the soil physicochemical properties and enzyme activities. We found that enzyme activities and available nutrients in the soil tended to decrease after long-term mulching. Analysis of bacterial community composition revealed that the endosphere may be another potential source of the root-associated microbiome of P. ostii, and the rhizoplane plays a selective gating role in the enrichment processes for P. ostii microbiome assembly. Long-term mulching affected the abundance of dominant bacterial communities in different root-associated compartments and reduced the bacterial richness in the endosphere, but increased bacterial interactions in each compartment, as well as between different compartments. We speculate that this is mainly related to the decrease of litter content and the serious degradation of polyethylene film after long-term mulching, which resulted in microplastics and other harmful substances entering the soil. Our study further explained the reasons for the harm of long-term film mulching on plants to guide the rational use of plastic film. KEY POINTS: •Soil enzyme activities and available nutrients decreased after long-term mulching. •Mulching affected the dominant bacterial abundance in different root-associated compartments. •Mulching increased bacterial interactions among compartments.