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Subject: Microbiology × Author: Bhagat, Poonam × End date: 2019 × Start date: 2010 × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Impact of long term organic and inorganic fertilization on microbial community and screening for cellulose degrading bacteria
    (Punjab Agricultural University, Ludhiana, 2018) Bhagat, Poonam
    Impact of long term incorporation of rice straw and inorganic nitrogen was studied on microbial communities, soil enzymatic activities and on soil parameters at different time intervals (0, 45, 90 and 120 DAS) for two consecutive years. The different doses of rice straw (0, 5, 7.5 and 10 t/ha) along with different doses of inorganic nitrogen (0, 90, 120 and 150 kg/ha) were incorporated in the wheat field. The first year results revealed maximum total bacterial count (8.31 log 10 cfu/g of soil), fungal count (4.89 log 10 cfu/g of soil), celllulse degrading bacteria count (7.11 log 10 cfu/g of soil) with 7.5 t/ha RS + 120 kg N/ha while actinomycetes count (7.14 log 10 cfu/g of soil), diazotrophic count (6.07 log 10 cfu/g of soil) with 10 t/ha RS alone at 45 DAS. The maximum dehydrogenase activity (23.96 µg TPF/g soil/hr), alkaline phosphatase activity (14.77 µg pNP/g soil/hr) and urease activity (330.0 µg urea/hr/g soil) observed at 45 DAS with 7.5 t/ha RS plus 120 kg N/ha. The microbial population and enzymatic activities found higher in second year over first year. The soil pH was found to be altered from 7.82 to 6.99 and EC from 0.219 to 0.201 dSm-1 with treatment 10 t/ha RS +120 kg N/ha whereas OC from 0.26% to 0.49% with 10 t/ha RS + 150 kg N/ha in two years at 120 DAS. The maximum soil available nutrients viz. nitrogen (136.7 kg/ha), phosphorous (29.94 kg/ha) observed with treatment10 t/ha RS + 150 kg N/ha, potassium (119.78 kg/ha) with treatment 7.5 t/ha RS + 120 kg N/ha at 45 DAS in the first year. The maximum straw and grain nitrogen (0.46%) and (1.37%), phosphorus (0.15%) and (0.38%), potassium (1.72%) and (0.53%) contents respectively in first year found with 10 t/ha RS + 150 kg N/ha. The maximum straw and grain yield (9.65 t/ha) and (6.28 t/ha) respectively observed in first year with 7.5 t/ha RS + 120 kg N/ha. The available nutrients and yield found higher in second year than first year. The cellulose degrading bacteria were isolated and halozone formation confirmed their cellulolytic activity. Seventeen isolates were characterized biochemically and most were positive for oxidase and catalase while negative for H2S test, indole test and MR-VP test and few were positive for citrate utilization, gelatin solubilization and starch hydrolysis. The functional characterization of isolates showed highest cellulolytic activity (1.44µg/ml), IAA production (34.85µg/ml), ammonia excretion (2.048µg/ml) and phosphate solubility (28.56 µg/ml) was exhibited by isolate SKPB3. Isolates were analysed phylogenetically by 16S rDNA sequencing. Isolates clustered in phylogentic trees indicated high similarity and the abundance of particular cellulolytic strains. Identification of representative cultures using parial sequencing of 16S rDNA revealed presence of Acinetobacter sp, Pseudomonas sp, Stenotrophomonas sp, Bacillus sp.