Gosal, S.K.Hardeep Kaur2019-02-022019-02-022018http://krishikosh.egranth.ac.in/handle/1/5810093406The present investigation was conducted to isolate and screen sulphur oxidizing bacteria from different soil samples including FYM, compost, mulching field, rhizospheric soil of rice, wheat, sugarcane, onion, potato, maize, chick pea, fodder crops and various mustard crops. A total of 40 different sulphur oxidizing bacteria (SOB) were isolated. Most of the bacterial isolates showed irregular, flat colonies of different colour , short rods and were gram negative. Biochemical characterization of the bacterial isolates indicated that most of these were oxidase, urease, citrate and catalase positive whereas negative for MR-VP test. Functional characterization of these isolates showed that SOB10, SOB38 and SOB5 produced maximum amount of sulphate ion 13.529, 9.780 and 9.638 mM, respectively. Out of the 40 SOB isolates, twenty seven isolates were able to solubilize phosphate whereas, twenty two isolates were able to solubilize zinc. Similarly, the respective isolates were analyzed quantitatively for phosphate solubilization and highest value was recorded with isolate SOB12 (4.285 μg/ml). Thirteen, among the isolates were found with higher ammonia production and the amount of ammonia excretion ranged between 0.311-28.88 μg/ml. The maximum amount (28.88 μg/ml) of ammonia was excreted by isolate SOB15. All the isolates were able to produce IAA, while isolate SOB15 produced maximum IAA (7.57 μg/ml) followed by isolate SOB7 (7.29 μg/ml) in tryptophan supplemented medium. Three sulphur oxidizers SOB10, SOB38 and SOB5 were found superior in terms of functional characteristics and tested for their biofertilizer potential. A pot experiment was conducted to study the effect of sulphur oxidizing bacteria on soil microbial dynamics, nutrient availability, plant nutrient uptake and growth parameters. Significantly higher bacterial (108 CFU x 107 /g soil), diazotrophic (76 CFU x 105 /g soil), PSB (48 CFU x 103 /g soil) and sulphur oxidizing bacteria (59 CFU x 105 /g soil ) population was recorded with the application of SOB Mix + consortium biofertilizer. Maximum count of fungi (25 CFU x 103 /g soil) was observed in SOB Mix + 100% sulphur whereas, actinomycetes (78 CFU x 105 /g soil) in uninoculated control. It was observed that increase in dose of sulphur from 75% to 100% resulted greater effect on microbial population of soil. Maximum soil alkaline phosphatase (3.21 μg/hr/g soil), dehydrogenase (56.62μg TPF/hr /g soil) and urease (668.10 μg/hr/g soil) activity was observed where SOB Mix + consortium biofertilizer + 100% sulphur was applied. Soil available N (243.02 kg/ha), P (15.77 kg/ha), K (121.88kg/ha) and S (14.773 ppm) were found highest in treatment with SOB Mix + consortium biofertilizer +100% sulphur. Plant N (1.68 g/plant), P (0.98 g/plant), K (1.57 g/plant) and S (1.98 g/plant) uptake was recorded highest with application of SOB Mix + consortium biofertilizer + 100% sulphur. Plant growth parameters viz, plant height, root-shoot dry weight, number of primary and secondary branches were maximum in treatment having SOB Mix + consortium biofertilizer +100% sulphur. The integrated use of SOB Mix, consortium biofertilizer and 100% sulphur boosts soil health and plant growth parameters of Gobhi sarson. Hence, sulphur oxidizing bacteria as SOB Mix stood successfuly on all grounds of a potential biofertilizer.ennullThesis