Abstract: A silicate bacterium K03 isolated from flue-cured tobacco rhizosphere was identified by morphologic characteristic, physiological and biochemical reaction, and phylogenetic tree based on 16S rDNA sequences. The results showed that this silicate bacterium belong to Enterobacter, may be Enterobacter asburiae. Silicate bacterium fertilizer preparaed using K03 was applied at a rate of 30 kg·hm-2 with minus 20% K dosage of full fertilizer when flue-cured tobacco was transplanted in plots. The numbers of rhizobacteria and rhizo-silicate bacteria significantly increased during the whole growth period, while the number of rhizoactinomycetes during the whole growth period and the number of rhizofungi at budding stage significantly decreased, compared to the control which was treated by 100% K of the recommended doses for tobacco. It indicated that the dominant microbial flora in tobacco rhizosphere altered to bacteria and silicate bacteria. The availability of mineral elements P, K, Ca, Cu, Zn, Fe and Mn, except Mg, in tobacco rhizosphere in tobacco topping stage were higher than that of the control, especially the availability of K was 27.08% higher than the control. The yield and production value of tobacco leaves were 7.38% and 5.47% higher than the control. The results suggested that silicate bacteria fertilizer reduced application rates of chemical K fertilizers, which could be an efficient way to produce high-quality and pollution-free tobacco leaves sustainably．

Key words: flue-cured tobacco, silicate bacteria, 16S rDNA, mineral element