Abilities of phosphate solubilizing bacteria isolated from sandy soils under rubber tree plantations of different ages in Northeast Thailand

In order to understand the impact of land use and the change which occurs within ecosystem services in rubber plantations, we must address the absence of knowledge on the influence of agricultural practices over biological processes within the soil.  This study describes the results of phosphate solubilizing bacteria (PSB) isolated from soil from different ages of rubber tree plantations in Northeast Thailand; where soils are mainly sandy, and retain a P deficiency.  PSB isolates were tested using different P sources [Tri-calcium Phosphate (Ca 3 (PO 4 ) 2 ) and Ferric Phosphate (FePO 4 )] on specific culture media [National Botanical Research Institute Phosphate Growth Medium, (NBRIP)] under controlled conditions.  Our results indicate that PSB isolated from rubber trees of different ages (5, 11, and 22 years) solubilized significantly higher amounts (P £0.01) of FePO 4 (601.45-631.63 mgP/L) and Ca 3 (PO 4 ) 2 (319.24-597.85 mgP/L).  The highest activity of solubilization was achieved in FePO 4 , which is the main form of insoluble phosphates in acidic sandy soil. Indole acetic acid (IAA) production was also observed in different ages and locations of the rubber plantations.  These results provide essential information for the influence of soil fertility within Thailand’s rubber plantations