Abstract

This experiment aimed to select new effective bacteria with high ability for cellulose decomposition and nitrogen fixation from various natural materials in order to improve organic fertilizers. CMC, N-free medium were used as culture broth and agar. The procedure determined 60 isolates of bacteria from decomposing rice straw, decomposing wood, cow manure, bagasse organic fertilizers, termite nest and the LDD1 inoculum. After that process, the selected bacteria (6 isolates) were identified for species level. All isolates were rod-shaped, gram-positive and spore forming bacteria that belonged to a bacillus group in species of Geobacillus stearothermophilus and Bacillus cereus which some species showed thermophillic character. Then, three sub-experiments were conducted. By considering the testing of the bacterial ability on cellulase activity, CRD with 3 replications were employed. The result showed that 1) G. stearothermophilus DW3 had the highest potential of CMCase activity (37.50 mm diameter), 2) G. stearothermophilus RS6 had the highest potential of FPase activity (4.942 mU/ml), 3) G. stearothermophilus RS2 had the highest potential of Avicelase activity (12.680 mU/ml) and 4) G. stearothermophilus DW3 had the highest potential of α-cellulase activity (4.289 mU/ml). In addition, regarding the study of bacterial nitrogenase activity, CRD with 3 replications were employed. The result showed that B. cereus CM6 had the most outstanding nitrogenase activity (278.788 nmolC₂H₄/ml/hr). In case of the study on the effectiveness of rice straw decomposition, the CRD with 3 replications were conducted. The study based on the standard index of organic fertilizer of Land Development Department (LDD), Thailand Ministry of Agriculture and Cooperatives. The result was found that the decayed rice straw in the inoculated treatment was qualified at 75 days, whereas the control treatment was not. The percentage of N, P and K in the inoculated treatments at 90 days was better than the previous period. In addition, C/N ratio decreased with times but the amounts of N, P and K increased. On the contrary, the percentages of N, P and K of the control treatment were satisfied while the C/N ratio was not in the standard level. The amounts of bacterial population among the inoculated treatments were not significantly different, but, they were significantly different between the inoculated and the control treatments.

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