This study was conducted with barley in greenhouse conditions in order to investigate seed inoculation with 5 different N-2-fixing (Bacillus licheniformis RCO2, Rhodobacter capsulatus RCO4, Paenibacillus polymyxa RCO5, Pseudomonas putida RCO6, and Bacillus CSU-142) and 2 different phosphate-solubilising (Bacillus megaterium RCO1 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 bacteria] strains fixed N-2 and significantly increased the growth of barley. Available phosphate in soil was significantly increased by seed inoculation with Bacillus M-13 and B. megaterium RCO1. Maximum NO3-N was found in soil after inoculation with N2-fixing Bacillus OSU- 142, followed by P. polymyxa RCO5 and R. capsulatus RCO4. Total culturable bacteria count increased in all treatments with time, whereas N-2-f'xing bacteria decreased with time, except with B. megaterium RCO1 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 bacteria] 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, RCO7, M-13, P. polymyxa RCO5, P. putida RCO6, and R. capsulatus RCO4. may be used in agriculture.
Erdoğan et al. (Mon,) studied this question.