A diverse group of soil bacteria found in the rhizosphere which can colonize plant roots and improve plant growth are designated as plant growth promoting rhizobacteria. The aim of this study was isolation and screening of different rhizobacterial strains for plant growth promoting characteristics and their ability to improve growth of two grass species, orchardgrass (Dactylis glomerata L.) and meadow fescue (Festuca pratensis Huds.). The strains investigated, belonging to the genera Azotobacter, Bacillus, Pseudomonas and rhizobial bacteria, showed various plant growth promoting traits, such as phosphate solubilisation, siderophore production, and indole-3-acetic acid (IAA) production. Co-inoculation of meadow fescue with Azotobacter chroococcum A2 and Sinorhizobium meliloti or Pseudomonas sp., and A. chroococcum A5 with S. meliloti, significantly increased shoot dry weight (SDW)(25-33%), as well as total N (26-33%), P (24-31%) and K (26-28%) contents in plants (mg pot ), compared to uninoculated control. In addition, inoculation of orchardgrass with A. chroococcum strain A1, as well as co-inoculation with B. megaterium and A. chroococcum A1 or A31, significantly increased SDW (51-59%) and total N (54-59%), P (51-74%) and K (49-55%) contents, compared to uninoculated control. Nitrogen percentage in SDW was slightly higher than sufficiency ranges, while K percentage was optimal in all treatments in both species. Phosphorous percentage was lower than sufficiency ranges as a consequence of very low soil P content. The results emphasize the potential of particular rhizobacteria to improve the growth of forage grasses.

In the field experiment, the effect of co-inoculation with Bradyrhizobium japonicum and two Pseudomonas sp. strains on seed yield and macronutrient uptake in soybean (Glycine max L.) was evaluated. The results showed that inoculation and co-inoculation of soybean seeds with B. japonicum and Pseudomonas sp. strains increased seed yield (from 65 up to 134%), and uptake of N, P, K, Mg, and Ca (kg ha-1 ) (from 65 to 167%), compared to the control plants (uninoculated, non-fertilized plants). Phosphorous concentration (mg kg-1 ) was increased in inoculated and co-inoculated treatments (up to 15%), compared to the control. The N%, as well as the concentrations of K and Ca, did not differ significantly among treatments and control. Magnesium concentrations were increased in mineral fertilized and co-inoculated treatments. Uptake of all nutrients was in significant correlation with seed yield, while the concentration of P only correlated with seed yield. The results showed that coinoculation with bradyrhizobial and some phosphate solubilizing bacteria can increase the seed yield and uptake of N and P in soybean.

Soil microorganisms, which are usually found in plant rhizosphere, have a wide spectrum of beneficial effects on the promotion of plant growth. The most comprehensively studied bacteria with these effects belong to the Bacillus genus. In this study, seven Bacillus isolates from Medicago sativa rhizosphere soils were isolated. Plant growth promoting characteristics of these isolates, such as production of indole-3aceticacid, siderophores and hydrogen cyanide were tested. The induction of wheat (Triticum aestivum) and barley (Hordeum jubatum) seed germination was evaluated in vitro. Isolate BMG2 produced the highest indole-3-aceticacid of 24.89 µg/mL. The length of roots of barley increased up to 60%, while the length of shoots of barley increased 2.23 times afterapplying isolatesPAZE-6 and BMG1, respectively. In addition, isolates BMG1, BMG2 and PAZE-6 improved germination of both types of seeds and showed ability to produce useful substances such as siderophores and indole-3-acetic acid. Further, these isolates could be used in the production of liquid crop additives that can improve the total yield of cultivated plants, especially barley.

In the present study the effects of Rhizobium inoculation and lime application on the mineral composition (N, P, K, Ca, Mg, Fe, Mn, Cu, Zn, B) of red clover (Trifolium pratense L.), in very acid soil were evaluated. Inoculation with Rhizobium leguminosarum bv. trifolii significantly increased shoot dry weight (SDW) of red clover plants (three times greater), as well as N, Mg, Fe, Mn and Cu contents in plants compared to the control. Application of lime and Rhizobium together, depending on the lime rate (3, 6 or 9 t ha-1 of lime) and the cut, increased SDW significantly, but decreased the contents of N, P, K, Mg, Mn, Zn and B in plants. Regardless of the changes, in all treatments in both cuts, contents of N, K, Ca, Mg, Mn and Zn in plants were among sufficiency levels (Mg content was elevated in the second cut), while Fe content was mainly high, as well as Cu (in the second cut). Contents of P and B in plants were somewhat lower than sufficiency levels, but above critical level. Therefore, red clover can be grown with satisfactory yield and mineral composition in acid soil with Rhizobium inoculation only, but the application of P and B fertilization is desirable.