Adding an insoluble phosphate source significantly
increased total PSB populations in the soil, which implies
that adding TCP was obviously beneficial for these
isolates to proliferate and survive. Hence, more available
P would be released into the soil and utilized by mung
bean plants. A similar increase in the PSB population and
available P content was observed by Yu et al. (2011). They
also observed a positive correlation between available
soil P content and PSB populations. A positive and
significant correlation between phosphate solubilizing
microorganisms and soil organic matter content was
previously reported by Venkateswarlu et al. (1984).
Other researchers (Vyas and Gulati, 2009) also reported
decreased soil pH in PSB-inoculated soil and indicated
organic acid production of both strains. Soil pH reduction
was found to be much lower than in the culture medium
(Table 1), which could be due to the buffering nature of
the soil used in the experiment (Gyaneshwar et al., 1998).