Document Details
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Document Type |
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Thesis |
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Document Title |
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Microbiological and Chemical Changes of Plant Residues During Decomposition in a Compost Environment التغيرات الميكروبيولوجية والكيميائية للمخلفات النباتية أثناء التحلل في بيئة الكومبوست |
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Subject |
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biological sciences department |
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Document Language |
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Arabic |
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Abstract |
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The main goal of this study was to investigate the composting of plant residues with highly efficiently cellulose decomposer strains. Five cellulose-decomposing Bacillus strains were isolated and the highly efficient two strains i.e., Bacillus megaterium and B. brevis were used in the composting process. The plant residues were collected from the mown grass of King Abdulaziz University and were composted for 60 days under aerobic condition. Temperature was measured daily, and samples were taken at 0, 12, 14, 33, 50 and 60 days and monitored for microbiological, physical and chemical analysis. Moisture content was maintained above 50% during the 50 days of composting process thereafter the compost was allow to dry naturally to reach 25% at the final product. Temperature of compost pile rose rapidly and reached its peak of 55ºC at day 4 and lasted above 45ºC more than 3 weeks. The pH value was decreased within the first 14 day of composting process to reach 5.0 and thereafter increased to reach 8.6 at the resultant compost. In addition, the organic matter and carbon content of plant residues were decreased gradually during the composting process and the biodegradability coefficient of the composting process was 0.5. Further, the C:N ratio was narrowed rapidly to reach 14.0 at the resultant compost. The macronutrient contents (N, P and K) were increased during the composting period to reach 3.0, 0.73 and 2.4% respectively at the resultant compost. The heavy metals content in the produced compost were within the safe range. The number of microbial population i.e., total microbe count, cellulose-decomposing microorganisms, fungi and actinomycetes were decreased gradually within the first 14 days of composting process then increased at 33 day except for actinomycetes, that continued to decline up to 50 day. After 50 day of composting process the number of microbial populations (total microbial count, cellulose- decomposing microorganisms and fungi) re-decreased up to the end of process. The total microbial count and cellulos-decomposing microorganisms were dominated during the process. The minimum recorded numbers of microorganisms were found by fungi population. The germination index of Lepidium sativum seed was carried out to determine the phytotoxicity of compost during the different stages of the process and it was correlated with pH value. The maturity and stability of the produced compost was determined according to C:N ratio ˂ 25, germination index ˃ 101, stable pH value decreasing in compost pile temperature and stable in microbial populations count. Properties of the resultant compost were 25% moisture content, 8.6 pH, 14.0 C:N ratio, 69% organic matter, 3.0% nitrogen, 0.73% phosphorus and 2.4% potassium. A pot experiment was carried out to evaluate the effect of resultant compost on maize growth parameters (plant height and dry weight) and nutrient uptake (NPK). The experiment included 10 treatments, 0.0% compost as control, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, 10, 15 and 20 % compost (w/w). Increasing compost rate more than 4.0% negatively affect plant growth. At the end of growth period (60 days), the resultant compost showed a high significant fertilizer value when applied at the rate of 4.0% (w/w) in comparison with control treatment (0.0% compost) and other treatments. It was surpassed the control treatment with 84% in dry weight, 45% in plant height, 87% in N-uptake, 96% in P-uptake and 88% in K-uptake. The present study recommended that the composting of plant residues using cellulose-decomposing microorganisms could be considered an option of waste management that is cheap, environmentally friendly and furthermore produces high value compost (fertilizer) to enhance plant growth. |
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Supervisor |
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Prof. Fahad Abdul Rahman Al-Fassi |
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Thesis Type |
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Master Thesis |
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Publishing Year |
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1434 AH
2013 AD |
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Added Date |
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Wednesday, November 27, 2013 |
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Researchers
| ابتهال عبد الله متولي | Motwali, Ebtihal Abdullah | Researcher | Master | |
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