Evaluation of the efficiency of plant growth promoting bacteria in reducing phosphate fertilizer application in wheat

The present study investigates the potential of rhizosphere and endophytic bacterial isolates isolated from the roots of wheat plant in terms of plant growth promoting (PGP) traits and their effect on the wheat yield and decreased phosphorus (P) fertilizer use. To this end, the isolated bacteria have been first screened for the production of indole-3-acetic acid (IAA) in the presence of tryptophan in the culture medium, and then the bacteria have been tested for their ability to dissolve inorganic and organic phosphates. In further laboratory studies, a factorial experiment has been conducted as a randomized complete block design with three replications over two-year field study (2017 and 2018). Experimental treatments include biological and chemical phosphorus fertilizer, the former with two levels (with and without bacterial inoculation) and latter (as the second factor) from triple super phosphate source with five (0%, 25%, 50%, 75%, and 100% of the full recommended fertilizer rate). Results from this experiment prove that supplementing 75% of the recommended P-fertilizer rate with bacterial isolates (co-inoculation with rhizospheric and endophytic bacteria) increases wheat growth indices and yield (747.40 g m-2), which are statistically equivalent to the full fertilizer rate without them. Based on these results, it is suggested that biofertilizer can be used as a fertilizer supplement to reduce the level of fertilizer use but cannot be a substitute for phosphorus fertilizer.