The Effect Of Ginseng Root Residue Tissue On The Structure And Function Of Soil Microbial Communities

Anthropogenic disturbances in ginseng cultivation on agricultural soil including(land preparation,shade,horticultural cleaning,fertilizer application and disease control)and longer growth cycles have led to frequent ginseng root rot and dramatic yield decline.Reducing tillage and retaining crop residues are important agricultural management practices to improve soil fertility,reduce erosion processes,prevent nutrient losses due to runoff and leaching,and increase soil microbial biomass.Crop residues are an important source of nutrients and control the composition of the soil microbial communities.The role of ginseng root residues left in ginseng cultivation soil on microbial communities and nutrient metabolism is unclear.In this study,different concentrations of ginseng root residues were prepared and added to diseased ginseng soil for 3 months after incubation,and macrogenomics was used to analyze the effects of different concentrations of ginseng root residues on the composition and function of microbial communities of diseased ginseng soil at different levels.Preliminary analysis of changes in microbial community composition and abundance of fungal pathogens after fallowing was also performed by amplicon sequencing.This study provides theoretical support for the resource utilization of ginseng root residues as agricultural waste and improvement of replantation barriers of farmland cultivation ginseng.The main results and conclusions are as follows:(1)Comparative analysis of changes in microbial community composition and function in farmland soil without ginseng cultivation and farmland soil with 4 years of ginseng cultivation.LEFSe screened differential bacteria and fungi with LDA > 4,19 differential bacteria and 40 differential fungi,respectively,and the results showed that the fungal community responded to changes in soil environment more than the bacterial community.The VFDB database based welch’st test showed that the abundance of genes related to the structure and function of pathogens were significantly higher in the ginseng-cultivated soil.(2)Analysis of the effect of changes in ginseng root residues concentration on the physicochemical properties and microbial community composition of ginseng cultivating soil after 3 months of soil incubation experiments.organic matter content was the lowest and effective phosphorus content was the highest in BQ3 and BZ3 treatments.The flower map and PCo A analysis showed that high concentrations of ginseng root residues had a significant effect on the species composition of the microbial community of cultivated ginseng soil.A variety of Streptomyces sp.with LDA>4 were screened in X3,BQ3 and BZ3 treatments using LEFSe.The results of bacterial community composition analysis showed that the addition of ginseng root residues,especially at high concentrations,increased the abundance of many beneficial bacteria.The results of fungal community network analysis demonstrated the most positive correlation is in BZ3 treatment,indicating that the cooperative relationship between fungal communities of ginseng diseased soil ecosystems was enhanced with increasing ginseng root residues concentration.(3)Effects of changes in ginseng root residues on carbohydrate enzyme,metabolic pathways,nitrogen metabolism and phosphorus metabolism in ginseng-cultivated soil.According to the CAZy database functional abundance table,the top 15 enzyme genes relative abundance in soil of groups X,BQ and BZ showed an increasing followed by a decreasing or decreasing trend,indicating that high concentrations of ginseng root residues may have inhibited enzyme activity.GH13,CBM32,GT2 and GT28 enzyme molecular genes annotated to species origin identified Streptomyces sp.as the dominant bacteria involved in enzyme catalysis.The functions annotated at the functional module and metabolic pathway level of the KEGG database were mainly amino acid metabolism,carbohydrate metabolism,cofactor and vitamin metabolism.These functions clustered in soil supplemented with 0.5 g or 2 g of ginseng root residues,indicating that the addition of ginseng root residues promoted biometabolism in ginseng-cultivated soil.Further analysis of the effects of ginseng root residues on nitrogen metabolism and phosphorus metabolism in ginseng-cultivated soil showed that both 0.5 g and 2 g of ginseng root residues increased the abundance of nitrification functional genes nar G,denitrification functional genes nap A,nor B,and nir K in the nitrogen cycle,but mainly increased the abundance of amino acid metabolism functional genes in nitrogen metabolism.Nine pathways related to phosphorus metabolism were screened,and 0.5 g and 2 g of ginseng root residues increased the abundance of functional genes of nine pathways related to phosphorus metabolism.(4)Some beneficial microorganisms such as Candidatus Solibacter,Rhizomicrobium,Gemmatimonas,Mortierella,Peziza,and Lecanicillium accumulated in relatively high abundance after fallowing.The relative abundance of Fusarium and Ilyonectria decreased by0.3% and 0.78%,respectively,in the soil cultivated with ginseng for two years after fallowing.The implementation of fallow management in ginseng cultivation can improve the composition and function of soil microbial communities and decrease major ginseng pathogens abundance.In conclusion,changes in the concentration of ginseng root residues were important factors influencing the composition and function of the microbial community in ginseng-cultivated soil,with Streptomyces sp.responding more to the addition of ginseng root residues.The presence of ginseng root residues promoted the abundance of functional genes for carbohydrase,nitrogen metabolism and phosphorus metabolism in ginseng-cultivated soil.Short-term fallowing reduced the abundance of ginseng pathogens.The implementation of agricultural management measures is essential to address the problems of low soil utilisation and low crop yield in agricultural fields.This study provides new insights for remediating the soil environment for ginseng cultivation and alleviating barriers to ginseng cultivation on farmland,and provides a theoretical basis for the resourceful use of ginseng root residues as agricultural waste.