Increases in tissue nutrients in treated plants following the
application of SP or PRP in inoculated soils may also be due to
the increase in the populations of PSB and possibly also the
indirect increases in the total native microbial populations
resulting from altered root exudation. Soil amendment with
SP or PRP in the present study increased the total soil
populations of PSB and also the population density of
phosphate-solubilizing NSA (data not shown) indicating that
by providing a substrate for M. endolithica, the SP or PRP
amendment was clearly supporting the proliferation and
possibly the survival of this isolate. The response of all
treatments which received only SP or PRP is expected to have
involved the activity and interaction with the indigenous
phosphate-solubilizing microflora of the soil. The stimulating
effecton phosphate-solubilizing microbial population by SP or
PRP may be due to the increased supply of available P.