| Salvia miltiorrhiza is a widely used bulk medicinal material,with its dry roots and rhizomes having high medicinal value.With the increasing demand for it in the medical industry,the cultivation area of Salvia miltiorrhiza has been gradually expanded.However,due to the environmental constraints on the growth of medicinal plants,the land area suitable for cultivation of Salvia miltiorrhiza is very limited,Leading to the gradual emergence of continuous cropping obstacles in the real estate area.The occurrence of succession disorders seriously restricts the yield and quality of Salvia miltiorrhiza.Therefore,the purpose of this paper is to study the changes of rhizospheric microorganisms and soil physicochemical properties in different growth stages(flowering period,rapid root growth period and harvesting period)and different years of continuous crop(1st year of planting,1st year of continuous crop,2nd year of continuous crop and 3rd year of continuous crop)of Salvia miltiorrhiza in Pingyi County,Shandong Province,and the correlation between rhizospheric microorganisms and soil physicochemical properties,so as to provide a theoretical basis for alleviating the continuous crop barrier and provide a certain reference for the sustainable development of the Salvia miltiorrhiza industry.The main contents of the study include:(1)In this study,soil p H gradually decreased with increasing years of continuous crop and showed the same trend in different growth stages of Salvia miltiorrhiza,all showing minimum values of 6.45,6.34 and 6.28 respectively at harvest,which may be related to organic acids and phenols secreted by the root system of Salvia miltiorrhiza.In this study,the content of organic matter at harvest gradually decreased with age,showing a maximum value in DZ and a minimum value in C3,which may be related to the continuous crop of Salvia miltiorrhiza.Soil fertility is inextricably linked to soil nutrient content,which also has an important influence on plant growth and development as well as soil quality and fertility.(2)In the present study,the dominant bacterial phyla in the inter-rhizosphere of Salvia miltiorrhiza mainly included Proteobacteria,Firmicutes,Acidobacteriota,Actinobacteria,Bacteroidota,Verrucomicrobiota and Chloroflexi.This result may be one of the reasons for the deterioration of the soil environment after continuous crop of Salvia miltiorrhiza.The relative abundance of Sphingomonas.in this study decreased by 35.79% at C3,thus allowing the accumulation of toxic substances,which may be related to the reduced yield of Salvia miltiorrhiza caused by continuous crop.The content of Candidatus＿Solibacter and Burkholderia-Caballeronia-Paraburkholderia gradually increased with increasing years of continuous crop,compared to DZ,respectively,while Bacillus,Pseudomonas and Sphingomonas gradually decreased.The change in the structure of the rhizospheric bacterial community of Salvia miltiorrhiza is not only related to the change in the physicochemical properties of the soil after succession,but may also be related to the accumulation of rhizospheric secretions or residues of Salvia miltiorrhiza.During the flowering stage,DZ bacterial community showed the highest abundance and diversity;during the rapid root growth stage,C3 bacterial community showed the minimum abundance and C2 showed the maximum;during the harvesting stage,C3 bacterial community showed a significant decrease in abundance and diversity.The variability between different samples may be related to the growth and metabolic characteristics of Salvia miltiorrhiza.(3)The dominant fungal phyla in this study included Ascomycota,Mortierellomycota,Basidiomycota,Chytridiomycota,Rozellomycota and Glomeromycota.At the genus level,as the number of years of continuous crop increases,so do the rhizospheric fungi Fusarium and Alternaria,which are the main causal genera for the development of root rot in Salvia miltiorrhiza,and the increase in harmful microorganism may be related to the accumulation of rhizosphere secretion of Salvia miltiorrhiza.During the flowering stage of Salvia miltiorrhiza,the fungal diversity and abundance of Salvia miltiorrhiza showed a trend of increasing and then decreasing with increasing years of continuous crop,while the ACE and Chao1 indices showed a trend of increasing and then decreasing with increasing years of continuous crop,while the Shannon and Simpson indices showed a trend of decreasing and then increasing with increasing years of continuous crop.The abundance and diversity of C3 were significantly higher than those of the other three years.The differences in rhizospheric microbial diversity and abundance of different plants were not only related to the number of years of cultivation,but also to factors such as climate,plant type and fertilization conditions.(4)In the correlation analysis of soil factors with rhizospheric bacterial community structure and diversity,it can be seen that total potassium,p H,total nitrogen,nitrate nitrogen and active phosphorus had the greatest effect on the diversity and abundance of rhizospheric bacteria of Salvia miltiorrhiza,while total potassium,total nitrogen,active phosphorus,p H and organic matter had the greatest effect on bacterial community structure.Other factors also had some influence on the microbial environment.Thus,it is suggested that changes in the structure of the inter-rhizosphere bacterial microbial community of Salvia miltiorrhiza are closely related to soil factors.In the correlation analysis between soil factors and rhizosphere fungal community structure,it can be seen that total potassium,total nitrogen,total phosphorus and p H have the greatest influence on the diversity index of Salvia miltiorrhiza fungi,while p H,available k,total nitrogen,total potassium and ammonium nitrogen have the greatest influence on the fungal community,and other factors also have some influence on the microbial environment.Therefore,it is suggested that the alteration of rhizospheric fungal microbial community structure of Salvia miltiorrhiza is closely related to soil factors.The alteration of the rhizospheric microbial community structure of Salvia miltiorrhiza is not only related to the alteration of the physicochemical properties of the soil after crop succession,but may also be related to the accumulation of rhizospheric secretions or residues of Salvia miltiorrhiza. |
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