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Abstract Application of biofertilizers in order to improve the growth and production of Black cumin (Nigella sativa) was conducted in this work. Two field experiments were carried out in El-Sheikh Zowayed North Sinai governorate, Egypt during the two successive seasons 200112002 and 200212003 to study the effect of using biofertilizers on the productivity of black cumin (Nigella sativa) and investigating the obtained seeds against some pathogens. The soil was amended with compost at the rate of 15 m 3/ feddan in the field experiment. It was supplemented with the recommended doses of Supper phosphate (P205 15.5%) l50Kg/Feddan and potassium sulfate 48% (l00 kg/feddan).The experiment included 4 types of treatments namely uninoculated and inoculated treatments with Azotobacter chroococcum and Bacillus megaterium alone or mixed. Each set of treatments contained three levels of mineral nitrogen fertilization; zero, 25 and 50 Kg /feddan under drip or rain irrigation. The used bacterial strains were prepared in microbiology lab of Desert Research Center. The soil and plant sampling to determine microbiological and chemical analyses were obtained at three stages of growth namely 60,150 and 210 days after planting. The efficiency of antimicrobial activities of oil content of each treatment against some pathogenic microorganisms was determined. SUMMARY The obtained results can be summarized as follows 1- Generally total microbial counts, densities of Azotobacter and densities of Bacillus megaterium under drip or rain irrigation increased at 60, 150 days and then decreased at 210 days. Also the increasing of the rates of mineral nitrogenous fertilization at 25and 50 Kg N/fed. with inoculation by azotobacters caused increment in the total number of microbial count, Azotobacter and Bacillus megaterium counts as compared with uninoculated treatments at 60 and 150 days. 2- Inoculation with Azotobacter chroococcum alone or mixed with Bacillus megaterium under drip irrigation in the presence of 25 Kg N/feddan gave the highest dehydrogenase activities. The rate of metabolic activity in soils under investigation show that all soil conditioning treatments achieved higher dehydrogenase activities than untreated samples in both seasons. 3- Organic carbon in the soil that was planted with Nigella sativa as affected by biofertilizer continuously decreased in the organic carbon content in all treatments as well as untreated soil up to the end of the experiment. 4- The increasing of mineral nitrogenous fertilization rates with inoculation by Azotobacter chroococcum alone or mixed with Bacillus megaterium under drip or rain irrigation resulted in a significant gradual increase in soil nitrogen content after 60 days from plant age as compared with the same mineral nitrogenous fertilization rates in case of absence of inoculation with Azotobacter chroococcum alone or mixed with Bacillus megaterium. 5-Inoculation of the soil with Azotobacter chroococcum and or Bacillus megaterium under drip or rain irrigation resulted in significant increases of available phosphorus or potassium after 60 days from planting as compared with uninoculated treatments. 6- Increasing of plant age caused an increase of plant heights in general. Increasing of mineral nitrogenous fertilization rates accompanied by dual inoculation with Azotobacter chroococcum and Bacillus megaterium under drip irrigation had a significant effect on increasing plant heights in comparison with uninoculated treatments. 7- The number of branches was increased with using half or full dose of mineral nitrogenous fertilization in the presence of dual inoculation under drip irrigation than individual inoculation or uninoculated treatments. There was not any increment in the number of branches with proceeding age of plant from 150 days. 8- By increasing age of plant, an increment in the fresh and dry weights of the plants was occurred till 210 days. Dual inoculation with Azotobacter chroococcum and Bacillus megaterium under drip irrigation resulted in a great increment in the fresh and dry weights than the uninoculated treatments or the individual inoculation especially at 50 Kg N/feddan, 9- The results indicate that the organic carbon in N sativa plants or seeds significantly increased by dual inoculation with Azotobacter chroococcum and Bacillus megaterium as well as by increasing inorganic N-fertilizer levels up to 50 Kg Ifeddan under drip or rain irrigation. 10- A significant increase in the total nitrogen content in N sativa plants has been occurred at 60 and 150 days of plant age while general decrease in total nitrogen exhibited at 210 days. Inoculation by Azotobacter chroococcum and lor Bacillus megaterium under drip or rain irrigation with increasing of mineral nitrogenous fertilization rates caused a general increase in the total nitrogen contents in the plants. 11- Total phosphorus or potassium of N sativa plants showed similar trend, as the phosphorus and potassium increased up to 150 days then decreased at 210 days. Inoculation with Azotobacter alone or mixed with Bacillus megaterium under irrigation caused highly significant increases for all treatments as compared with uninoculated ones. 12- Dual inoculation with Azotobacter chroococcum and Bacillus megaterium and amended with half or full dose ofNfertilizer under drip irrigation caused a significant increase in the total nitrogen content of seeds. The increment was higher than those which resulted from mineral fertilization only. 13- The same trend of total nitrogen content was also noticed for total phosphorus or potassium in seeds of Nsativa which increased with dual inoculation with Azotobacter and Bacillus megaterium under drip irrigation when using half or full dose of N-fertilizer caused the highest values comparing with uninoculated treatments. 14- Inoculation with Azotobacter chroococcum and Bacillus megaterium as solely or mixed inoculation under drip irrigation in the presence of 50 Kg N/feddan gave the highest yield of N. sativa seeds or oil yield in comparison with uninoculated treatments or rain irrigation. 117 15- The inhibitory effects of black cumin essential oil were studied against three groups of test microorganisms. The highest inhibition zones were observed by oils obtained by using dual inoculation in the presence of half dose of inorganic N-fertilizer when it was used against some food-borne pathogens, phytopathogenic bacteria or phytopathogenic fungi. 16- The obtained oil when using dual inoculation exhibited decreases in the minimum inhibitory concentration (MIC) for all test microorganisms especially when amended with half or full doses ofN-fertilizer. |