Inoculation of phosphate-solubilizing bacteriaBacillus thuringiensisB1 increases available phosphorus and growth of peanut in acidic soil

Phosphate-solubilizing microorganisms play an important role in plant nutrition by enhancing phosphorus (P) availability to roots through converting the insoluble phosphates into soluble ions. We isolated phosphate-solubilizing bacteria (PSB) from acidic soil (Ultisols) in the field from the layer of 0–150 mm at a tea garden located at 28°38′26″ N and 116°24′27″ E. The capacity of bacterial isolates to solubilize mineral phosphate was tested on aluminum phosphate (AlPO4) in liquid medium. Among these PSB, isolate B1 (identified as Bacillus thuringiensis) exhibited the maximum P-solubilizing ability and was particularly efficient at solubilizing AlPO4 (up to 321 mg L−1) in vitro. The isolate B1 was inoculated to an acidic soil to study its effect on phosphate solubilization and growth of peanuts (Arachis hypogeae). The Olsen-P in the tested soil increased from 14.7 to 23.4 mg kg−1, with solubilization of 16.4 mg kg−1 soil of Occluded-P after 14-day incubation. The inoculation by B1 significantly increased plant height (from 37.7 to 45.7 cm), number of branches (from 34.0 to 52.7 per plant), hundred-seed weight (from 42.1 to 46.9 g) and crude protein content (from 243.5 to 268.2 g kg−1 dry weight). The phosphate-solubilizing B. thuringiensis strain B1 showed potential as a biological phosphorus fertilizer.