Combined Detoxification Effects Of Arbuscular Mycorrhizal Fungi And Earthworms On Soil Microplastic Pollution

Intensive vegetable planting has led to a large amount of plastic wastes(notably mulch)in the soil environment,inducing widespread concern of microplastics(MPs)contamination.Currently,how to reduce the stress of soil MPs pollution on crop growth has become an urgent need for sustainable and healthy agriculture.In the soil-crop ecosystems,both arbuscular mycorrhizal(AM)fungi and earthworms have positive effects in improving plant nutrient and resistance,showing a potential for combined application of both.Thus,both polyethylene terephthalate(PET)and lowdensity polyethylene(LDPE)were tested in this study.Firstly,the differential effects of different input levels(0.1% and 1%)of the two MPs on soil AM fungal diversity and pepper(Capsicum annuum L.)growth were compared.Secondly,the combined effects of earthworm(Eisenia foetid)and AM fungus(Funneliformis caledonium)on pepper growth in a sterilized but MPs-contaminated soil were revealed.Thirdly,the regulation effects of earthworm inoculation on indigenous AM fungal function in a MPs-contaminated soil were investigated.The main results are as below:(1)Input 1% of MPs resulted in significant changes in soil chemical properties,and disturbed soil AM fungal community structure,diversity,colonization and pepper growth.However,input 0.1%of MPs induced relatively smaller effects,and there were some differences between the effects of PET and LDPE.In general,LDPE caused more serious damage to the soil-pepper system than PET.(2)In a sterilized soil amended with AM fungal inocula and 0.1% of LDPE,inoculation of earthworms benefited mycorrhizal colonization in pepper roots.The earthworm and AM fungus also had interactive or combined effects in increasing soil alkaline phosphatase(ALP)activity and plant phosphorus nutrition,reducing MPs phytotoxicity,and increasing plant biomass and fruit yield.(3)Inoculation of earthworms had positive effects on the community structure of indigenous AM fungi in MPs-contaminated soils,and significantly increased observed richness and Shannon index rather than Simpson index and Pilou’s evenness of AM fungi in the LDPE-contaminated soil.Thus,AM fungal abundance,colonization,soil ALP activity and plant growth were all increased.In conclusion,MPs pollution adversely affected soil AM fungal community structure,diversity and vegetable growth,and a higher input level means a stronger inhibition effect.Earthworm had positive effects on mitigating the inhibition effects of MPs on pepper growth via mobilizing and exerting the ecological functions of indigenous AM fungi.Therefore,this study provides a scientific basis for the safe utilization of MPs-contaminated vegetable soils.