Application of liquid microbial inoculants on legume seeds is a sustainable agricultural practice that can improve plant nutrient uptake and increase crop productivity. Inoculants should provide long-term survival of rhizobia in the final product and after application, to legume seeds. Ten different medium formulations of microbial inoculants were examined (yeast mannitol broth with the addition of agar, sodium-alginate, calcium chloride, glycerol or ferric chloride and combinations thereof) for the survival of the efficient nitrogen-fixing rhizobium, Sinorhizobium (Ensifer) meliloti L3Si strain. The most suitable liquid inoculant for survival of L3Si during a storage time of 150 days was the medium formulation containing glycerol in combination with agar or sodium-alginate. Alfalfa seeds were pre-inoculated with four formulations (yeast mannitol broth (YMB), YMB with agar (1 g L-1), YMB with 1 or 5 g L-1 sodium-alginate) for up to three months. Seeds pre-inoculated and stored for one month produced successful alfalfa plants. The nitrogen content in alfalfa obtained from pre-inoculated seeds one month before sowing was adequate and ranged from 3.72-4.19%. Using S. meliloti-based liquid inoculants for alfalfa and application of the pre-inoculation technique can increase the quality of alfalfa crops and reduce cultivation cost.

Aims: This research aimed to isolate and characterize nonrhizobial endophytic bacteria from root nodules of Medicago sativa L. and Lotus corniculatus L. with plant growth-promoting characteristics and to test its activity in a pot experiment with acid soil. Methods and Results: Out of 44 nonrhizobial isolates, the majority exhibited indole-3-acetic acid (IAA) production; 29 produced siderophores, few isolates performed phosphate solubilization and/or produced lytic enzymes, while 30% of isolates showed notable antifungal activity. The most promising strains were identified as members of Bacillus, Pseudomonas and Serratia genera, based on 16S rRNA. Bacillus megaterium DZK1BH exhibited the overall best attributes for plant growth promotion and positively influenced the growth of L. corniculatus and Dactylis glomerata. Conclusions: Root nodule endophytic B. megaterium DZK1BH could potentially be used as a biofertilizer for growing L. corniculatus L. and D. glomerata L. in acid soils, while Bacillus mojavensis L3 is a candidate for further antifungal potential investigation. Significance of Impact of the Study: The use of root nodule endophytic bacteria with PGP traits may find its future application in organic agriculture, as their utilization could decrease the use of chemical fertilizers and pesticides and simultaneously promote plant growth, especially in soils with low production quality.

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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.

This study was conducted to test the hypothesis that plant growth promoting rhizobacteria (PGPR) can promote the growth of Italian ryegrass, Lolium multiflorum Lam. as well as the growth and nodulation of subsequent alfalfa, Medicago sativa L. In a pot experiment, the influence of PGPR on yield and nitrogen content of Italian ryegrass and alfalfa was studied with the aim to improve their growth and provide effective alfalfa nitrogen fixation under unfavourable soil conditions. Plants were inoculated with seven strains belonging to Sinorhizobium meliloti, Azotobacter spp. and Enterobacter sp. A beneficial effect on yield and N-assimilation in Italian ryegrass was obtained due to the inoculation of the plants with Azotobacter vinelandii and some Sinorhizobium meliloti strains. In addition, Italian ryegrass seed inoculation with particular rhizobial strains the year before alfalfa growing provided abundant nodulation and better growth of alfalfa.

One of the most common soil types in area of western and south-western Serbia is the Eutric Cambisol. In order to determine biogenity of this soil type, the presence of total microflora, fungi, actinomycetes, ammonifiers, Azotobacter sp. and oligonitrophils, as well as dehydrogenase activity were examined. Samples were taken from soils used in two different ways (plough fields and meadows). Standard microbiological methods of inoculation a certain decimal dilution on appropriate nutrient media were used. No correlation between the number of microorganisms and type of the soil usage was found. In localities that were under plough fields and meadows, the presence of Azotobacter sp. was confirmed, as an indicator of soil fertility. The correlation of dehydrogenase activity with the total number of microorganisms was not observed. Agrochemical analysis showed acidic to weakly acidic soil reaction, medium to high percentage of organic matter, low content of easily available phosphorus and high content of easily available potassium. There was no correlation between chemical properties of the soil and the number of microorganisms in examined soil type.

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.

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