الفهرس 
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Abstract
This Thesis consist of two parts: the first part concern the isolation, characterization and identification of N2- fixing Azotobacters isolates. Thirty one rhizosphere collected representative soil samples were collected for isolation the N2-fixing Azotobacter isolates. After purification the isolates were tested for their N2 fixation activity, phosphates dissolving ability, production of plant growth promoting substances, siderophores, exopolysaccharides and some enzymes production. The purified isolates were identified as Azotobacter chroococcum. Out of these purified isolates four isolates were found to be more significant in all the activities tested. The selected isolates were as used individual and/ or mixture to prepare the effective rhizobacterial inoculants. The results of the firist part show that the most active isolates Azo.4, Azo.5, Azo.9 and Azo.23 were found to be more significant in the production of the forementioned activities as compared with the other purified isolates.
The second part consist of pot and field experiments to evaluate the effectiveness of azotobacters inoculants and/or different doses of inorganic nitrogen fertilization on microbial colonization, CO2 evolution and growth performance of black cumin and fennel plants.
Data clearly show that the highest densities of total microbial flora, Azotobacter, CO2 evolution were detected in the rhizosphere of black cumin and fennel plants. Inoculated with the mixture of rhizobacterial inoculum influenced the growth and multiplication of azotobacters in rhizosphere of both medicinal plants. The plant growth performance, weight of 100 seeds, fixed and volatile oil, neutral up take were significantly affected by inoculation with mixture of biofertilizers and half or ¾ dose of mineral N-fertilizer in black cumin, and fennel plants. The effect of crude oils of black cumin and fennel on some human pathogenic bacteria namely, Staphylococcus aureus , Escherichia coli , Salmonella sp , Shigella sp and Listeria monocytogens, were studied in vitro. It was found that the crud fixed and volatile oil extracted from the seeds of both plants
have powerful antibacterial properties against these diverse genus of bacteria.The influence was different and depending on the bacterial
strain.
Results revealed that azotobacters inoculant conjugated with half or ¾ dose of mineral N fertilizer significantly increase the microbial colonization and COR2R evolution. All the mixture of azotobacters treatments significantly increase microbial densities and COR2R evolution can pared to the uninoculated treatments in both type of plants. The inoculation mixture significantly influenced the growth
and multiplication of azotobacters in the rhizosphere of both plants.
The plants growth performances were significantly affected by inoculation with the mixture of bio fertilizers and ½, ¾ dose of Nmineral fertilizer.