Inoculation of phosphate-solubilizing bacteria Bacillus thuringiensis B1 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 degrees 3826 N and 116 degrees 2427 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.