This study was conducted with barley in greenhouse conditions in order to investigate seed inoculation with 5 different
N2-fixing (Bacillus licheniformis RC02, Rhodobacter capsulatus RC04, Paenibacillus polymyxa RC05, Pseudomonas putida RC06, and
Bacillus OSU-142) and 2 different phosphate-solubilising (Bacillus megaterium RC01 and Bacillus M-13) bacteria in comparison to
control and mineral fertiliser (N and P) application. Among the strains used in the present study, 6 plant growth promoting
rhizobacteria (PGPR) stimulated indole acetic acid (IAA) production and 3 of them stimulated phosphate solubilisation; all bacterial
strains fixed N2 and significantly increased the growth of barley. Available phosphate in soil was significantly increased by seed
inoculation with Bacillus M-13 and B. megaterium RC01. Maximum NO3-N was found in soil after inoculation with N2-fixing Bacillus
OSU-142, followed by P. polymyxa RC05 and R. capsulatus RC04. Total culturable bacteria count increased in all treatments with
time, whereas N2-fixing bacteria decreased with time, except with B. megaterium RC01 inoculation. The data suggest that seed
inoculation of barley with plant PGPR increased root weight by 17.9%-32.1% as compared to the control, and increased shoot
weight by 28.8%-54.2%, depending on the species. N2-fixing bacterial inoculation significantly increased uptake of N, Fe, Mn, and
Zn by barley. The production of hormones is suggested to be one of the mechanisms by which PGPR stimulate barley growth.
Effective Bacillus species, such as OSU-142, RC07, M-13, P. polymyxa RC05, P. putida RC06, and R. capsulatus RC04, may be used
in agriculture
