The aim of this paper is to improve the potassium content of tobacco leaves and provide bacterial resources for high-quality flue-cured tobacco production.In this study,pot experiments were carried out with 20 plant growth promoting bacteria(PGPR)as candidate strains and Yunyan 87 as materials,the effects of PGPR on flue-cured tobacco potassium content was explored.The good PGPR strains were screened,and used to produce bio-organic fertilizer.Their effect on the chemical quality,agronomic properties and plant biomass of flue-cured tobacco leaves,the physicochemical properties and microbiological properties of soil were studied performed.The main results are as follows:(1)Three excellent potassium-promoting strains,i.e.DB30-2(Sinorhizobium fredii),DY15-2(Bacillus sp.)and SZ201(Serratia marcescens),were screened from 20 PGPR strains based on their effects on inreasing potassium content in flue-cured tobacco leaves,soil potassium content and soil enzyme activity.(2)The biological organic fertilizer was produced by using the screened excellent bacteria promoting potassium absorption of flue-cured tobacco leavies.The pot experiments were carried out,the results showed that compared with control(T1),bio-fertilizer with single PGPR strain(T2),and bio-fertilizer with mixed strains(T3)can significantly improve the flue-cured tobacco plant leaf number,stem size,leaf size and leaf area coefficient,and the flue-cured tobacco plant biomass;At the same time,both bio-fertilizers ciould increase the potassium content of flue-cured tobacco leaves 4.11%-11.83%,reduce the protein content,and reduce the total nitrogen,nicotine and sugar content of tobacco leaves,and make the flue-cured tobacco quality according the national standards,and the nitrogen-alkali ratio and sugar-alkali ratio was more coordinated.Compared with T3,T2 can improve the chemical quality of tobacco better.(3)Compared with T1,both T2 and T3 reduced soil available potassium content,and increased slowly available potassium content,available phosphorus and organic matter in tobacco planting soil,which enhanced the soil nutrient availability.Application of bio-fertilizer could increase the biomass of soil culturable bacteria and actinomycetes at the later stage of flue-cured tobacco growth and development;both T2 and T3 could increase the activity of soil alkaline phosphatase and invertase,T3 could also significantly improve the activity of catalase,peroxidase and polyphenol oxidase at the late vigorous growth period of flue-cured tobacco.Both T2 and T3 could increase the soil microbial biomass carbon and nitrogen,and T3 was better than T2 treatment.Application of bio-fertilizer reduced the richness of soil bacterial community,but T2 treatment increased the diversity of soil bacterial community.T2 and T3 treatment could increase the relative abundance of soil Nocardioides,T2 and T3 treatmenthad had different effects on Blastomonas and Spongolomonas.The community structure of each treatment varied greatly,and the contents of available potassium,available potassium,available phosphorus,phosphatase and sucrase were the dominant environmental factors affecting the soil microbial community structure.Overall,from the perspective of increasing the potassium content of flue-cured tobacco leaves,improving the quality of tobacco leaves,and improving soil bacterial communities,SZ201(Serratia marcescens)is an excellent bacterial strain to make bio-fertilizer. |