Effect Of Arbuscular Mycorrhizal Fungi On Improvement And Restoration Of Degraded Soil In Ionized Rare Earth Mining Area Of Southern Part Of Jiangxi Province

Ion-type rare earth is a unique precious rare earth resource in China.There are abundant ion-type rare earth resources in southern Jiangxi,known as the “ rare earth kingdom ”.The disordered mining of ion-type rare earth ore for many years has brought serious ecological and environmental problems,such as large area of topsoil damage,soil fertility decline,soil acidification,soil leaching agent residue,etc.Traditional soil improvement methods often have disadvantages of high cost and difficult to promote.The combination of biological modifiers and functional microorganisms provides a new idea for ecological restoration of ion-type rare earth tailings degraded soil.In this study,the degradation soil of ion-type rare earth tailings in Xinfeng County,Ganzhou City,Jiangxi Province was taken as the research object.The composite measures(biochar + fly ash +surface vegetation planting)were used to improve the soil.Phospholipid fatty acid(PLFA)method was used to observe the effects of different restoration models on the rhizosphere soil microbial community of navel orange,and other analysis was used to explore the relationship between soil microbial community and biomass during the restoration of ion-type rare earth tailings soil.On this basis,pot experiments were conducted to explore the potential role and mechanism of ‘ Arbuscular mycorrhizal fungi(AM fungi)+ amendments(biochar + fly ash)+ phytoremediation ’ in soil improvement of ion-type rare earth tailings in southern Jiangxi.The main results are as follows :(1)The treatment of Trifolium repens + 5 % biochar(SBC2)had a good promotion effect on the contents of soil organic carbon(SOC),total glomicin(TG)and easily extracted glomicin(EEG).The treatment of adding 1 % biochar(BC1)had better stability of soil aggregates,but the treatment of planting Trifolium repens + biochar had more obvious effect on the formation of soil aggregates.SBC2 significantly increased soil nutrient content and soil pH.(2)Different improvement methods had a significant effect on the rhizosphere soil microbial biomass of plants.The rhizosphere soil microbial biomass of Trifolium repens treatment was generally higher than that of other treatments.The treatment of planting Trifolium repens + 1 % biochar(SBC1)significantly increased the biomass of fungi and Gram-negative bacteria(G-).SBC2 significantly increased the biomass of AM fungi.SCK(planting Trifolium repens without biochar)significantly promoted Gram-positive bacteria(G+),actinomycetes and total microbial biomass,and showed a positive correlation.It can be seen that planting Trifolium repens on the surface and adding a certain amount of biochar have a positive effect on the rhizosphere soil microbial community and soil structure in the process of reclamation of ion-type rare earth tailings degraded soil,which shows certain advantages in the ecological restoration of rare earth tailings soil.(3)Inoculation with AM fungi(Septoglomus viscosum,Sv and Claroideoglomus claroideum,Cc)could significantly promote the growth of plants grown on ion-type rare earth tailings soil,and the mycorrhizal infection status of the tested plants was significantly positively correlated with plant biomass and plant height,showing good mycorrhizal effect.Compared with the control treatment,the plant and AM fungi had a good symbiotic relationship(mycorrhizal infection rate was between 21 % and 43 %),and the infection of the double inoculation strain on the plant was higher than that of the single inoculation strain.When P50 was added,the mycorrhizal infection rate of plants decreased compared with that without P(P0).AM fungi inoculation also significantly promoted the absorption of N,P,K and other nutrients,and significantly promoted the accumulation of nutrients in plants.Single Sv significantly promoted the absorption and accumulation of nitrogen in plants,while double Sv and Cc significantly promoted the absorption and accumulation of phosphorus in plants.(4)Inoculation of AM fungi significantly improved soil nutrient accumulation and soil physicochemical properties.The effect of single inoculation of Sv and Cc on the accumulation of soil nutrient content was more obvious than that of Mixed Inoculation of Sv and Cc.The content of total nitrogen(TN)in soil was significantly increased after adding start-up phosphorus(P50),but the content of total phosphorus(TP)in soil was significantly affected by adding start-up phosphorus(P50).At the same time,inoculation of AM fungi reduced soil pH and promoted the environmental adaptability of mycorrhizal symbionts.The content of soil organic carbon was significantly increased by the application of Sv.The contents of EEG and TG in soil were significantly increased by double inoculation,and there was a significant positive correlation between TG and organic matter.Inoculation of AM fungi had a significant contribution to soil carbon pool.