No abstract

In the present study, to evaluate the conversion of intracellular PHB to methane gas, excess activated sludge with and without the accumulation of polyhydroxybutyrate (PHB) was subjected to anaerobic digestion. Excess activated sludge was collected from a laboratory activated sludge reactor and a part was fed with acetate in aerobic condition to obtain excess activated sludge with PHB accumulation. Then, excess activated sludge with and without PHB accumulation were mixed with anaerobic digested sludge, and the degradation of PHB and formation of methane gas were monitored during anaerobic fermentation at 37 o C. For excess sludge with PHB accumulation, more than 75% of PHB was degraded only within the initial 2 days of incubation. Besides, 25% more methane gas was produced from excess sludge with PHB than without PHB accumulation. High production of methane gas indicates that PHB accumulated inside the cells of heterotrophic bacteria can easily be digested in anaerobic digestion process.

A study was conducted to test the influence of different inorganic fertilizers (phosphorous and potassium) on the nodulation and growth of Dalbergia sissoo grown in the nursery. Before seeds sowing, different combinations of P, K fertilizers were incorporated with the nutrient-deficient natural forest soils, and then amended with cowdung (soil: cowdung = 3:1). Nodulation status (nodule number, shape, fresh weight, dry weight and color) in the roots and the plant growth parameters (length of shoot and root, collar diameter, fresh and dry weight of shoot and root) were recorded 60 days after seeds sowing. Nodulation status and growth of the plants varied significantly (P<0.05) in the soils amended with fertilizers in comparison to the control. The highest nodule number (62), fresh (0.50 g) and dry (0.07 g) weights were recorded with the dose of PK at the rate of 160 kg/hm 2 . Nodule shape and color also varied widely in different treatments. In case of plant growth parameters, shoot and root length, collar diameter, fresh and dry weight of the plants took on a significant difference (P<0.05) among various combination of fertilizers. From the study, it is revealed that PK at the rate of 160 kg/hm 2 fertilizer with soil and cowdung mixture (soil: cowdung = 3:1) is recommended for optimum growth and nodule formation of D. sissoo in degraded soils at a nursery level.

A study was carried out to determine the influence of different types of sludges (municipal, industrial and residential) on field germination, growth and nodulation of L. leucocephala seedlings in the nursery. Before sowing of seeds, different combinations of sludges were incorporated with the nutrient deficient natural forest soils. Field germination, nodulation status and physical growth parameters of seedlings (shoot and root length, vigor index, collar diameter, leaf number, fresh and dry weight of shoot and root and total dry biomass increment) were recorded after three and six months of seed sowing. Field germination, nodulation status and growth parameters were varied significantly in the soil amended with sludges in comparison to control. The highest number of nodule was recorded from soil amended with residential sludge (1:1) and highest fresh and dry nodule weight was also found from the same combination in both three and six month old seedlings. In case of growth parameters, the highest growth was recorded from soil and residential sludge (1:1) combination compared to control. From the study, it can be recommended that soil amended with residential sludge (1:1) provide better field germination, growth and nodule formation of L. leucocephala in degraded soil.

This study was performed in five villages of Sandwip Upazila, Chittagong district with a view to identify the tree resources, utilization pattern and economic return of major fruit and timber tree species. Information collected from a total of 60 households ranging from marginal, small, medium and large categories. Number of plant species increased with the increase of homestead area. A total of 33 plant species were recorded from the homegarden, of which 19 were fruit and 14 were timber tree species. Considerable number of vegetables was also planted under the shade of the homestead trees. The investment analysis showed that average benefit-cost ratios were greater than one, net present values were positive and internal rate of returns were more than 10%. Long term investment on horticulture and timber tree species is highly profitable if species like Artocarpus heterophyllus, Cocos nucifera, Tectona grandis and Swietenia macrophylla are planted.