الفهرس 
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Abstract
Antibiotics are used in agriculture to improve livestock growth, beekeeping, and fish farming. However, most antibiotics are poorly absorbed in the intestine of animals and are excreted unchanged. Fertilizer is a reservoir for both antibiotic resistant bacteria and antibiotic resistance genes. Livestock soil application, poultry manure, and agricultural irrigation wastewater with high concentrations of antibiotics are major sources of antibiotic contamination of soils, groundwater, and sediments. As well as only oxytetracycline and streptomycin have fit the necessary requirements to be used to resist fire blight disease in apple and pear orchards. The main objective of this study was to assess the impact of the oxytetracycline and streptomycin application at 7 levels (0, 5, 10, 20, 50, 70 and 150 mg kg-1) of OTC and (0, 5, 10, 20, 50, 100 and 150 mg kg-1) of STR on soil community including bacteria growth represent by optical density (OD), soil respiration within 35 incubation day and soil enzymes activity (dehydrogenase and alkaline phosphatase) at three concentrations (0, 10 and 70 mg kg-1) of OTC and three concentrations (0, 10 and 100 mg kg-1) of STR after just 1,8 and 35 day of incubation experiment in three triplicates. Germination experiment (as primary root length) of two types of seeds (wheat and sorghum) was also carried out to investigate the tested OTC and STR. Main results of study summarized as follow: ♦ The greatest negative effect of either OTC at all concentrations (0,5,10,20,50,70, and 150 mg kg-1) or STR at (only 5,20,50 and 150 mg kg-1) on bacterial growth in contaminated soil by them was between days 8 and 14 of the experiment. The inhibitory effect continued until day 14 in some concentrations of the two antibiotics, then the microbial activity and bacterial growth increased, and by the end of the experiment, the natural balance in bacterial growth returned.
♦ No significant effect of either OTC or STR was observed on soil respiration rate at different concentrations of the two antibiotics throughout the experiment. ♦ All used concentrations of OTC and STR had inhibitory effect on alkaline phosphatase activity in soil after 8 days of incubation. By end of incubation, high concentrations of both antibiotics stimulated alkaline phosphatase activity by 1.4 and 1.3 times respectively more than the control. ♦ Low concentration of STR (10 mg kg-1) and high concentration of OTC (70 mg kg-1) stimulated dehydrogenase activity 3 and 4 times more than the control after 8 days of incubation.
♦ There was an inhibitory effect on the growth of primary roots of wheat seeds after being treated with all different concentrations of OTC with significant difference between 5, 50 and 150 mg kg-1 by 44.3%, 62.7% and 72.9% respectively compared to the control.
♦ While only concentration (20 mg kg-1) of streptomycin has a stimulating effect on the growth of the primary root of wheat. 35
♦ No significant difference was observed between the control and low concentrations 5, 10 and 20 mg kg-1 of each of oxytetracycline and streptomycin on the initial root growth of sorghum seeds, while higher concentrations of them led to a decrease in root length with an average ratio 75.3 for OTC and 63 for STR compared to the control.