Effects Of Plastic Film Mulching On Microbial Communities In Different Compartments Of Farmland

Plastic film is a widely used agricultural practice in the world,and has been widely used in China with many advantages,which has greatly promoted the development of China’s agriculture,but also brought serious plastic pollution problems to farmland soil.Biodegradable plastic(Biodegradable mulch film,BDMs)because of its environmental friendliness gradually replace the traditional plastic mulch thus alleviate the current severe plastic pollution problems.Although BDMs is environmentally friendly compared with traditional PE films,it is not known whether BDMs will have an adverse impact on the environment in the process of degradation of plastic debris because it is easy to decompose and break into plastic debris and accumulate in the soil after use.At present,the research on the environmental impact of plastic mulch mainly focuses on water,and the research on soil ecological environment is less,and most of the research on soil is still in the stage of simulated pot experiment and shaking bottle experiment,and the potential ecological risk caused by long-term or short-term use of BDMs on actual farmland is unknown.In addition,the use of plastic film will not only accumulate a large amount of plastic film residue in the soil,but also produce plasticizers(phthalate esters),microplastics and other derivative pollution substances,which also poses a great threat to the farmland ecological environment.Therefore,it is very important to study the ecological impact of plastic mulch on different areas of actual farmland,so as to accumulate experience for solving the problem of soil plastic pollution in the future.In this paper,the effects of polyethylene plastic film(PE)and biodegradable plastic film(BDMs)and different thicknesses of BDMs were compared on the characteristics of bacterial communities in biofilms,non-rhizosphere soil and rhizosphere soil intervals and the effects of plastic film on flower production.The results showed that:(1)For the structure and composition of the bacterial community,the type of plastic film,the thickness of the biodegradable plastic film,and the field zoning significantly affected the bacterial community structure in different areas of the field,especially in the rhizosphere soil(P<0.001).When the effects of mulch type and BDMs thickness on bacterial communities in rhizosphere soil intervals were considered separately,the bacterial communities in rhizosphere intervals were significantly different within and between groups.Under the BDMs treatment in the QT4 group,the microbial community in the rhizosphere soil interval had high diversity and richness,which indicated that the use of BDMs with appropriate thickness had a positive effect on the rhizosphere bacterial community.In terms of species composition,under BDMs treatment,the relative abundance of Acidobacteria increased significantly at the phylum level,while Pseudxanthomonas,Flavobacteria,and nitrocellulococcus were enriched at the genus level.BDMs promoted the accumulation of beneficial microorganisms in crop growth.(2)The results of Sourcetracker analysis showed that only a small part of the microbiota enriched in the biofilm interval transferred from the bulk soil and rhizosphere soil compartments after different types of plastic film were used in the actual farmland,and the proportion of microbiota transferred from the above two soil compartments was also different with different types of plastic film.Plastic film is a special microbial colonization space different from natural substrate,so there are unique biomarkers in the biofilm formed on the surface of PE and BDMs.LEf Se analysis showed that Pseudxanomonas and glutamicobacter were biomarkers of PE and BDMs biofilm intervals,respectively.They could degrade plasticizers left in plastic mulch and similar components of BDMs,respectively.Therefore,these two genera could be used as potential degradation bacteria to alleviate plastic mulch contamination.(3)Through the analysis of microbial co-occurrence network,we found that BDMs with appropriate thickness could promote the interaction relationship between bacterial communities in rhizosphere soil interval,and make the bacterial network in rhizosphere soil interval more complex and stable.compared PE with BDMs,it was not difficult to find that BDMs significantly increased the number of nodes and edges of bacterial network in rhizosphere soil compartment,and the network topology,such as avg K,avg CC and HD,was better than that of PE.Comparing BDMs with different thickness,it was found that the bacterial network in the rhizosphere soil compartment of QT4 group was more complex and stable,and too thick or too thin BDMs was not conducive to the formatia of complex and stable bacterial network.Under BDMs conditions,the enrichment of beneficial bacteria in rhizosphere soil and the closer and more stable interactions between bacteria greatly increased peanut yield.From this study,comparing the effects of different types of plastic film on bacterial communities in different compartments of farmland,it was found that the bacterial communities in rhizosphere soil sections were significantly different due to different types of plastic film,and BDMs had a positive effect on bacterial communities in rhizosphere soil compartments.At the same time,compared the effects of BDMs with different thicknesses on bacterial communities in farmland,it was clear that the appropriate thickness of BDMs was conducive to the interaction between bacteria and bacteria in rhizosphere soil,so as to improve crop yield.The above results provide new insights into the ecological effects of different plastic film on different compartments of farmland and the subsequent solutions to plastic pollution problems.