Plastic mulch film residues in agriculture: impact on soil suppressiveness, plant growth, and microbial communities

Plastic mulch film residues have been accumulating in agricultural soils for decades, but so far, little is known about its consequences on soil microbial communities and functions. Here, we tested the effects of plastic residues of low-density polyethylene and biodegradable mulch films on soil suppressiveness and microbial community composition. We investigated how plastic residues in a Fusarium culmorum suppressive soil affect the level of disease suppressiveness, plant biomass, nutrient status, and microbial communities in rhizosphere using a controlled pot experiment. The addition of 1% plastic residues to the suppressive soil did not affect the level of suppression and the disease symptoms index. However, we did find that plant biomasses decreased, and that plant nutrient status changed in the presence of plastic residues. No significant changes in bacterial and fungal rhizosphere communities were observed. Nonetheless, bacterial and fungal communities closely attached to the plastisphere were very different from the rhizosphere communities with overrepresentation of potential plant pathogens. The plastisphere revealed a high abundance of specific bacterial phyla (Actinobacteria, Bacteroidetes, and Proteobacteria) and fungal genera (Rhizoctonia and Arthrobotrys). Our work revealed new insights and raises emerging questions for further studies on the impact of microplastics on the agroecosystems.数十年来，农用塑料地膜残留持续在农田土壤中累积，但截至目前，学界对其对土壤微生物群落及生态功能造成的影响仍知之甚少。本研究针对低密度聚乙烯（low-density polyethylene）与可降解地膜的塑料残留，探究其对土壤抑病性及微生物群落组成的影响。本研究通过受控盆栽实验，探究了锐顶镰孢（Fusarium culmorum）抑病土壤中的塑料残留对根际（rhizosphere）病害抑病水平、植物生物量、营养状况及微生物群落结构的影响。向该抑病土壤中施加1%的塑料残留，并未改变其抑病能力与病害症状指数。但研究发现，塑料残留存在时，植物生物量出现下降，且植株营养状况发生改变。根际细菌与真菌群落未出现显著变化。不过，紧密附着于塑料圈（plastisphere）的细菌与真菌群落与根际群落差异显著，且潜在植物病原菌的占比显著升高。塑料圈中富集了特定的细菌门类：放线菌门（Actinobacteria）、拟杆菌门（Bacteroidetes）与变形菌门（Proteobacteria），以及真菌属：丝核菌属（Rhizoctonia）和节丛孢属（Arthrobotrys）。本研究为微塑料对农田生态系统影响的相关领域提供了全新的认知，并提出了若干亟待开展后续研究的新兴科学问题。