الفهرس 
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Abstract
Organic farming represents one of organic farming systems which avoid the direct use of common agricultural fertilizers, chemical pesticides and plant growth substances. Organic farming depends on organic amendments for activating the biological role in soil. With the recent interest in organic farming, the present work aims at isolation some specialized soil bacteria, which harness atmospheric nitrogen, solubilize phosphate or decompose silicate. The isolates were applied through a strategy of integrated nutrient supply by using a judicious combination of mineral fertilizers, composted garbage and bacterial inoculants. Investigation the bacterial inoculation on growth of wheat and soil fertility in presence of a low dose of mineral fertilizer (nitrogen) and composted garbage was studied. The results obtained can be summarized as follow: Six isolates from the nitrogen fixer Azotobacter sp., five isolates from Azospirillum sp., ten from phosphatesolubilizing bacteria and five from silicate decomposing bacteria were isolated from the rhizosphere of wheat, broad bean, lupine, tomato and clover plants. The isolates were purified and identified. The isolated strains belonged to Azotobacter chroococcum Azospirillum lipoferum phosphatesolubilizing bacteria Bacillus subtilis and silicate decomposing bacteria Bacillus circulans. The efficiency of nitrogen fixers ranged from 66.372.9 mol C2H4/ml culture/hour of Azotobacter chroococcum and from 81.2103.5 nmol C2H4/ml culture/hour of Azospirillum lipoferum. The efficiencies of the phosphate dissolving strains of Bacillus subtilis in solubilizing tricalcium phosphate ranged from 7.726.34 mg water soluble phosphorus/100 ml culture after 28 days incubation at 30 C. The efficiencies of silicate dissolving strains of Bacillus circulans in decomposing biotite ranged from 7.414.6 mg water soluble potassium/1000 ml culture after 8 weeks incubation at 30 C. The most efficient strains were selected for the preparation of the bacterial inocula. Bacterial inoculation of wheat grains, with single or composite inoculum of Azotobacter chroococcum, Azospirillum lipoferum, Bacillus subtilis and Bacillus circulans, increased significantly plant heights, root and shoot dry weights, tillering degree, 1000grains weight, grain yield, straw yield and nutrientuptake by grains and straw. Tested bacterial inoculants in the absence of other fertilizers treatments yielded 50% grain yield compared to the yield of the full nitrogen dose treatment. Bacterial inoculations, composted garbage, N fertilization and their interactions led to significant increase in N, P and K uptake in grains and straw. Composite bacterial inoculation in presence of 10 ton composted garbage and 90 kg nitrogen per feddan increased the total bacterial counts in wheat plants to 21.9 x 106 cfu/g dry soil after 120 day of wheat cultivation. Also, nitrogen fixers counts in rhizosphere of wheat plants increased with time. The counts of Azotobacter chroococcum and Azospirillum lipoferum reached 22.88 x 103 and 59.67 x 103 cell/g dry soil at the end of experiment, as compared to the beginning of the experiment with 0.91 x 103 and 1.60 x 103 cell/g dry soil, respectively. Mixture of associative bacterial inoculants with organic and mineral fertilizer increased the phosphatedissolving bacteria counts. These counts reached 37.62 x 103 cfu/ g dry soil after 120 days compared to 1.7 x 103 at the start of the experiment. Biofertilization and mineral & organic fertilization led to an increase in counts of silicatedissolving bacteria, which reached 14.97 x 103 cfu/g dry soil after 120 dry compared to 0.872 x 103 cfu/g dry soil in the starting of the experiment. The following study recommend by the possibility of using the bacterial inoculum Azospirillum lipoferum, Azotobacter chroococcum and composted garbage in the presence of low dose of mineral fertilizer (nitrogen).