Evaluation of Plant Growth Promoting Characteristics in Commercial Biofertilizers of Azotobarvar, Potabarvar, Ruein and Phosco

In this study, three domestic biofertilizer samples including Azotobarvar, Potabarvar, Ruein, and a sample of Indian biofertilizer called Phosco were studied in terms of microbial population count and plant growth promoting characteristics. The results of plate counting revealed that Potabarvar had no alive bacterial population, but the number of viable cells of Azotobarvar, Ruein and Phosco were 3.5 × 108, 5.2 × 108 and 6.9 × 103 CFU g-1, respectively. Moreover, two isolates (Az1 and Az2), three isolates (R1, R2 and R3) and three isolates (P1, P2 and P3) were isolated in Azotobarvar, Ruein and Phosco, respectively. The in-vitro results of plant growth promoting characteristics showed that in the solid LG medium R1 and Az2 and in the liquid LG medium, P1, R1 and Az2 and had the highest nitrogen fixation, respectively. In phosphate solubilizing from tricalcium phosphate, Az1 and Az2, in potassium releasing ability, Az1 and P1 isolates from biotite and Az1 and P2 from muscovite and in production of auxin P1 in the presence of tryptophan had the highest performance, respectively. The isolates P1, P3, R1 and R3 had antifungal activity against Fusarium solani. Summarizing the results of microbial population counts as well as plant growth promoting characteristics showed that the both Ruein and Azotobarvar biofertilizers were in desirable condition and Phosco biofertilizer, despite having some growth-promoting properties, lacked a sufficient microbial population and the Potabarvar biofertilizer lacked the microbial population.