Identification and effect of a nitrogen-fixing bacterium in flue-cured tobacco rhizosphere

The Azotobacter N05 isolated from flue-cured tobacco rhizosphere is identified as Alcaligenes sp, likely Alcaligenes faecalis, by using the phylogenetic tree constructed from 16S rRNA gene sequences, its physiological indexes and biochemical reactions. To our knowledge, this is the first report on azotobacter Alcaligenes faecalis in flue-cured tobacco rhizosphere. Applying to transplanted flue-cured tobacco, the numbers of azotobacter under the combination of N05 azotobacter fertilizer (30 kg/ha) and 80% N dosage of the full fertilizer amount (B+80% N) are 3.6 times of those of the full N fertilizer (FN) treatment, while the numbers of actinomyces under the combination treatment are significantly deceased. In addition, compared to the FN, the soil available contents of P, K, Ca, Cu, Zn, Fe, and Mn in tobacco rhizosphere at the tobacco toping stage under the B +80% N are increased by2.51% 46.08%. The average contents of N in de-enzyme tobacco leaves at different growth stages under the B +80% N are higher than those under the FN. These results indicate that the amount of azotobacter and availability of mineral elements are enhanced by using azotobacter fertilizer in flue-cured tobacco production when N dosage is reduced moderately.