Effects of earthworm activity and P-solubilizing bacteria on P availability in soil

The effects of phosphate solubilizing bacteria (Bacillus megateriumi) (PSB) and earthworms (Pheretima guillelmi and Eisenia fetida) on phosphorus (P) turnover and transformation in soil were investigated in a laboratory experiment lasting for 21 days. The treatments included soil + P. guillelmi (SW1), soil + E fetida (SW2), soil + B. megaterium (SB), soil + P. guillelmi + B. megaterium (SBW1), soil + E fetida + B. megaterium (SBW2), and the control with sterilized soil (control) only. The results showed that the number of B. megaterium, was enhanced in all treatments especially those with earthworms added when compared with the control. Activities of acid phosphatase (pH = 6.5) increased in all treatments, especially in the presence of P. guillelmi with or without PSB (64% and 38%, respectively). Significant increases in both inorganic P and water-soluble P were observed in treatments involving B. megaterium and earthworms when compared with the control. Inoculation of both earthworms and PSB had significant effects on microbial growth, enzymatic activity, and thus enhanced the release of available P. The dual inoculation of earthworms and bacteria further accelerated P transformation. Different performances observed for the earthworm species were probably due to their different feeding habits and physiology.