The application of PGPR for the ecological restoration under
natural soil conditions has been little explored. In this respect, the
application of organic amendments to the soil, prior to the
inoculation of beneficial microorganisms, as PGPR, might be
recommended. As previously reported organic amendments are
able to increase soil microbiota activity, particularly in degraded
soils under semiarid conditions (Medina et al., 2004). The
beneficial effects of organic amendments include provision of
plant nutrients, increased humus content and thereby increased
water-holding capacity, improved soil structure, and increased
microbial activity (Caravaca et al., 2002). The extractions of sugar
from the sugar beet produced agrowastes, but these products can
only be used as organic amendment after biological transformation
processes. In this context, the application of fermented
agrowaste with microbiologically-solubilized rock-phosphate has
been assayed for improving plant performance under stress
conditions (Medina et al., 2004). Fermented agrowaste can be
used as energy sources for heterotrophic microorganisms such as
PGPR as suggested by Bashan and Holguin (1998).