The aim of the research was to examine the effect of rhizospheric bacteria Azotobacter chroococcum, Pseudomonas fluorescens (strains 1 and 2) and Bacillus subtilis on the growth and yield of onion and on the microorganisms in the rhizosphere of onion. The ability of microorganisms to produce indole-acetic acid (IAA), siderophores and to solubilize tricalcium phosphate (TCP) was also assessed. The experiment was conducted in field conditions, in chernozem type of soil. Bacillus subtilis was the best producer of IAA, whereas Pseudomonas fluorescens strains were better at producing siderophores and solubilizing phosphates. The longest seedling was observed with the application of Azotobacter chroococcum. The height of the plants sixty days after sowing was greater in all the inoculated variants than in the control. The highest onion yield was observed in Bacillus subtilis and Azotobacter chroococcum variants. The total number of bacteria and the number of Azotobacter chroococcum were larger in all the inoculated variants then in the control. The number of fungi decreased in most of the inoculated variants, whereas the number of actinomycetes decreased or remained the same.

The effect of inoculation with Pseudomonas fluorescens and Bacillus subtilis on the yield of fresh and dry mass of English ryegrass (Lolium perenne L.) as well as on the number of rhizospheric microorganisms was studied. The microorganisms were introduced into the soil before sowing. The control plots were not inoculated. The number of microorganisms was determined after the third mowing. The yield was determined after the first, second and third mowing. In comparison with the control, after the first and second mowing, there was a statistically significant increase in the fresh and dry mass in both inoculated variants whereas after the third mowing, a statistically significant increase in the yield of fresh mass was recorded only in the variant with B. subtilis. The use of B. subtilis had a better effect on the total yield of the fresh and dry mass of English ryegrass. The number of the investigated groups of microorganisms, apart from actinomycetes, increased in the inoculated variants. Inoculation of P. fluorescens affected the increase of total number of bacteria and aminoheterotrophs whereas inoculation of B. subtilis affected the increase of the number of azotobacter and fungi.

Microalgae application in agriculture is an alternative measure that could be highly beneficial to plants. The application of microalgae Chlorella vulgaris S45 and its effect on plant growth and pigment content in Swiss chard were investigated. In the treatments, 5% and 10% algal suspensions were applied by spraying on plants and in soil, respectively. C. vulgaris S45 affected the initial growth of Swiss chard and the content of photosynthetic pigments positively. The correlation analysis proved the existence of statistically significant interdependency between chlorophyll a (Chl a) content and leaf number (r = 0.876 at p < 0.05), and chlorophyll b (Chl b) content and fresh leaf weight (r = 0.783 at p < 0.05).

The present study was carried out to investigate the influence of crop rotation and fertilization on the number of different groups of microorganisms. Soil samples were taken from the following treatments: 1. Monoculture of maize, 2. Maize-wheat (without fertilization), 3. Maize-wheat (with fertilization), 4. Maize-soybean-wheat (with fertilization), 5. Pasture soil, 6. Forest soil under oak, from three depths: 0-10 cm, 10-20 cm, and 20-30 cm in May and October 2012. Microbiological analyses included the determination of total number of bacteria, number of fungi, actinomycetes, aminoheterotrophs, and azotobacter. The number of investigated groups of microorganisms was higher in May on average. Fertilization did not affect the number of investigated groups of microorganisms. Crop rotation positively affected the total number of bacteria and the number of aminoheterotrophs in soil under maize.

The aim of the study was to investigate ability of Pseudomonas sp. Q4b, Bacillus sp. Q5a and Azotobacter chroococcum strain 8 to enrich a population of plant growth promoting rhizobacteria (PGPR) in rhizosphere and thus enhance maize growth (Zea mays L.). Experiments were carried out under greenhouse and field conditions, on a chernozem soil. In vitro screening for PGP properties showed significant difference between indole-3-acetic acid (IAA) and siderophores production and phosphosolubilization between Pseudomonas sp. Q4b and Bacillus sp. Q5a. Pseudomonas was estimated as a better producer of hydrogen cyanide (HCN) and siderophores than Bacillus. Bacterial treatments had a significant effect on the number of investigated microbial groups in rhizosphere, and maize growth and yield. Co-inoculation had an advantage compared to single inoculation, while in case of single strains, better effects were achieved in Pseudomonas and Azotobacter treatments. Inoculation increased the number of azotobacters (103.25%), pseudomonads (82.29%) and aerobic spore-forming bacteria (52.65%) as well as height (17.15%) and dry weight (35.48%) of maize plants. The highest plant height was recorded in treatment with Pseudomonas and Bacillus. The highest dry weight and yield were recorded in the treatment with mixture of these three strains.

Because of their huge biodiversity and metabolic capabilities, the application of microorganisms as bioremediation agents is a way to enhance pollutant degradation. The aim of this research was to investigate the potential of five strains of Pseudomonas sp. as possible bioremediation agents. Strains are from the Collection of the Microbiology Department, Faculty of Agriculture, Novi Sad. Bacterial strains were cultivated in King?s B liquid medium and incubated in shak?er at 28?C. Starter culture was obtained after 24h, CFU 108. This 24h old bacterial culture was used for the analysis of influence of five different natural naphthenic acids. Bacterial growth was determined spectrophotometrically through optical density, after 24h and 48h of growth. Our results showed that two bacterial strains (PS V1 and PS2) had better growth after 48h as they used C from the petroleum derivates. The growth of these strains was increased by 72% and 25% with deri?vates concentration of 10-5 mol/cm3 and 10-6 mol/cm3, respectively. The results of this research showed the potential of certain bacterial strains as bioremediators. [Projekat Ministarstva nauke Republike Srbije, br. TD 31027 i br. III 043002]

No abstract

The purpose of this study is to investigate the microbial activity and the number of different groups of microorganisms in the soil under organic agricultural systems.A range of analyses was conducted on soil samples taken from calcareous chernozem soils managed under organic (7 sites) and conventional agricultural systems (1 site). Laboratory measurements were performed in the Laboratory of Microbiology, Faculty of Agriculture, Novi Sad. The total number of bacteria, actinomycetes, fungi, aminoheterotrophs and azotobacters was determined using the dilution method. Soil dehydrogenase activity was measured spectrophotometrically.The greatest number of the Azotobacter sp. bacteria was recorded in the soil devoted to pumpkins (132.61 × 10 2 ) and in the soil devoted to apples (126.39 × 10 2 ). The greatest number of aminoheterotrophs (1786.05 x10 6 ) and the total number of bacteria (1370.82 x 10 6 ) and actinomycetes (235.45 × 10 4 ) were determined in the soil devoted to carrots. Fungi were more abounded in the soil devoted to chard (36.82 ×10 4 ) than in the soil devoted to other plants. The research results show that the soil devoted to wheat in organic production indicated a greater number of aminoheterotrophs, total bacteria, actinomycetes and fungi, whereas only the number of Azotobacter sp. was greater in the soil devoted to wheat in the conventional agricultural system. The highest dehydrogenase activity level was determined in the soil devoted to radishes, whereas the lowest dehydrogenase activity level was determined in the soil devoted to apples.