The Effect of Plant Growth Promoting Rhizobacteria on Barley Seedling Growth, Nutrient Uptake, Some Soil Properties, and Bacterial Counts

Abstract

This study was conducted with barley in greenhouse conditions in order to investigate seed inoculation with 5 different
\nN2-fixing (Bacillus licheniformis RC02, Rhodobacter capsulatus RC04, Paenibacillus polymyxa RC05, Pseudomonas putida RC06, and
\nBacillus OSU-142) and 2 different phosphate-solubilising (Bacillus megaterium RC01 and Bacillus M-13) bacteria in comparison to
\ncontrol and mineral fertiliser (N and P) application. Among the strains used in the present study, 6 plant growth promoting
\nrhizobacteria (PGPR) stimulated indole acetic acid (IAA) production and 3 of them stimulated phosphate solubilisation; all bacterial
\nstrains fixed N2 and significantly increased the growth of barley. Available phosphate in soil was significantly increased by seed
\ninoculation with Bacillus M-13 and B. megaterium RC01. Maximum NO3-N was found in soil after inoculation with N2-fixing Bacillus
\nOSU-142, followed by P. polymyxa RC05 and R. capsulatus RC04. Total culturable bacteria count increased in all treatments with
\ntime, whereas N2-fixing bacteria decreased with time, except with B. megaterium RC01 inoculation. The data suggest that seed
\ninoculation of barley with plant PGPR increased root weight by 17.9%-32.1% as compared to the control, and increased shoot
\nweight by 28.8%-54.2%, depending on the species. N2-fixing bacterial inoculation significantly increased uptake of N, Fe, Mn, and
\nZn by barley. The production of hormones is suggested to be one of the mechanisms by which PGPR stimulate barley growth.
\nEffective Bacillus species, such as OSU-142, RC07, M-13, P. polymyxa RC05, P. putida RC06, and R. capsulatus RC04, may be used
\nin agriculture.