Comparative P solubilizing efficiencies of five acid soil bacteria incubated with calcium, aluminium and iron phosphates

As acid soils of Odisha have been facing a major constraint in phosphorus availability, application of native P solubilizing bacteria could be promising as well as ecofriendly step towards sustainable P availability for crop growth and development. To address the problem of P availability in acid soil of Bhubaneswar, Odisha, rhizosphere soil samples (pH ≤ 5.50) with rice – pulses (green gram/black gram) cropping system were collected and phosphate solubilising bacteria were isolated. In vitro characterization of the PSB isolates were conducted with calcium, aluminium and iron phosphates to recover soluble P. All the five strains i.e. Bacillus cereus BLS18 (KT582541), Bacillus amyloliquefaciens CTC12 (KT633845), Burkholderia cepacia KHD08 (KT717633), Burkholderia cepacia KJR03 (KT717634), Burkholderia cepacia K1 (KM030037) could solubilize Ca3(PO4)2, AlPO4, FePO4, and Fe3(PO4)2. Higher recovery of soluble P was with Ca3(PO4)2 while the least was with AlPO4. All the strains exibited a trend similar with respect to P recovery i.e. Ca3(PO4)2 > FePO4 > AlPO4 > Fe3(PO4)2. B. amyloliquefaciens CTC12 was most efficient in solubilizing calcium and iron phosphates whereas B. cepacia KHD08 recovered maximum P with aluminium phosphate. All the inorganic salt fortified mediums showed a significant decline in pH which necessitated the identification of compounds present in the mediums. Organic acids viz; acetic, citric, gluconic, lactic, malic, succinic, tartaric acids in the mediums were identified by HPLC. Tartaric acid was only found in the mediums supplemented with AlPO4. B. amyloliquefaciens CTC12 and B. cepacia KHD08 showed promising results in in vitro analysis of P solubilization. The present study is focused on problematic acid soils where phosphorous is unavailable and mostly fixed with aluminium and iron ultimately making it unavailable for the crops to take up. This leads to unbalanced and frequent use of chemical fertilizer. Hence the study is a significant attempt to characterize native PSBs with capacity to solubilize Al-P and Fe-