Browsing by Author "Kitojo, D. H."

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Potentials of lesser known and lesser utilized indigenous agroforestry timbers in Kilosa District, Morogoro Tanzania
(International Journal of Education and Research) Makonda, F. B. S.; Augustino, S.; Gillah, P. R.; Ishengoma, R. C.; Kitojo, D. H.; Ruffo, C.; Eriksen, S.; Msanga, H. P.
Some physical and mechanical properties of Uapaca Kirkiana, a lesser-known timber species from Tanzania
(Tanzania Journal of Forestry and Nature Conservation, 2007) Gillah, P. R.; Makonda, F. B.; Ishengoma, R. C.; Kadala, B.; Kitojo, D. H.
This study was carried out to determine some physical and mechanical properties of Uapaca kirkiana a lesser known timber species growing in public land near Iyondo Catchment Forest Reserve, Kilombero District, Morogoro, Tanzania. A total of 3 trees were used in the study. Preparation of test samples and laboratory procedure to determine some physical and mechanical properties followed standard methods. Analysis of variance was used to determine the variation between and within trees and regression analysis was used to determine relationship between wood basic density and mechanical properties. The results showed that Uapaca kirkiana has whitish sapwood and dark brown heartwood, with a mean basic density of 518.14 kg/m3. The properties of Uapaca kirkiana were as follows: modulus of elasticity (7185.69 N/mm2), modulus of rupture (59.7 N/mm2), work to maximum load (0.06 mmN/mm3), total work to failure (0.07 mmN/mm3), shear strength parallel to the grain (11.86 N/mm2), compression strength parallel to the grain (34.4 N/mm2) and cleavage strength (20.21 N/mm width). On axial direction, the modulus of elasticity, total work to failure, compression strength parallel to grain and cleavage strength were directly proportional to its basic density while modulus of rupture, work to maximum load and shear strength parallel to the grain were inversely proportional implying that Uapaca kirkiana is suitable for activities, which require high modulus of elasticity, total work to failure, compression strength parallel to the grain and cleavage strength. On radial direction modulus of elasticity, modulus of rupture, work to maximum load, compression parallel to the grain and cleavage strength were directly proportional to basic density while shear parallel to the grain was inversely proportional to basic density. Compared to Khaya anthotheca, the timber species found in the same location and market; it was found that the timber of Uapaca kirkiana had modulus of rupture and compression parallel to the grain far lower than those of Khaya anthotheca, while the work to maximum load, total work to failure, shear strength parallel to grain and modulus of elasticity were almost the same. Due to the similarity in some of their physical and mechanical properties, the wood of Uapaca kirkiana may berecommended to substitute Khaya anthotheca in wood works that require medium density wood like in decoration where colour is considered an important aspect for appearance and in cabinet, panel and furniture making though it is not adequate in high-class strength joinery.
Some physical and strength properties of lesser known aphloia theiformis timber from Lushoto Tanga, Tanzania
(Tanzania Journal of Forestry and Nature Conservation, 2008-07-14) Gillah, P. R.; Makonda, F. B. S.; Hussein, I.; Augustino, S.; Kitojo, D. H.
Some physical and strength properties of lesser known Aphloia theiformis timber grown in and around Magamba Forest Reserve, Lushoto district, Tanga region were determined. A total of three sample trees were randomly selected and felled for this study. Test samples for moisture content, basic density and Strength properties determination were prepared and tested according to Lavers (1969), BS 373 (1957), ISO 3130 (1975), ISO 3131 (1975), ISO 3133 (1975) and ISO 3349 (1975). It was observed that Aphloia theiformis timber has a sapwood and heartwood colour ranging from creamcoloured to whitish pink resembling that of Grevillea robusta. The average basic density was 519 kg/m3 with a standard deviation of 4.2 which can be classified as medium-density timber. The basic density showed a slight decrease from butt end to top end. Regarding strength properties, Aphloia theiformis timber had a mean modulus of rupture of about 55.8 N/mm2 and modulus of elasticity of about 3854 N/mm2. The work to the maximum load was about 0.06mmN mm-3, while total work averaged 0.08mmN mm-3. The compression and shear parallel to the grain were 37.4 and 12.6N mm-2 respectively. Furthermore, all strength properties of Aphloia theiformis were positively correlated with basic density. The properties of this timber were also comparable to properties of Grevilea robusta and are always rated the same by timber dealers. While Aphloia theiformis had higher tearing strength than Grevillea robusta, the modulus of rupture and compression parallel to the grain values were comparable. Aphloia theiformis can therefore substitute Grevilea robusta in many areas of its application.
The effect of clay on the persistence of BTi toxicity against mosquito larvae in Morogoro, Tanzania IA
Kilonzo, B. S.; Madoffe, S. S.; Maliondo, S. M. S.; Msanya, B. M.; Mabagalla, R.; Kitojo, D. H.
The effect of clay on the persistence of BTi toxicity against mosquito larvae in Morogoro, Tanzania IA
(2001) Kilonzo, B. S.; Madoffe, S. S.; Maliondo, S. M. S.; Msanya, B. M.; Mabagalla, R.; Kitojo, D. H.
Laboratory colonies of Anopheles gambiae and Culex quinquefasciatus were reared from parental larvae obtained from the Ifakara Health Research Centre and septic tanks ill Morogoro Municipality respectively. Water ponds (1M3 ) were constructed at selected sites and left open for mosquitoes to breed ill freely. Various concentrations of Bti crystals were-mixed with varying concentrations of clay and tested against third instar larvae of each species at various periods of time post-preparation. A total of 60 larvae (20 x 3) were exposed to each mixture in the laboratory, and each- experiment was replicated four times. Mortality rates were recorded after 241t. exposure. The observations revealed that for every concentration of Bti crystals used, the toxicity on both species of mosquitoes was less persistent in crystal/clay mixtures than in crystals alone. It was also shown that such persistence was much less in mixtures containing large concentrations of clay (5mg/ml) titan in those containing low concentrations (0.05 - 0.5 mg/ml) of clay. It wasfurther observed th at the toxicity against Culex and Anopheles larvae was more persistent in mixtures containing higher concentrations of Bti crystals (0.12 - 0.3 ug/ml) titan ill those containing low concentrations (0.03 - 0.06 ug/ml) of the toxin. Furthermore, it was observed that C. quinquefasciatus larvae succumbed to Bti crystal/clay mixtures for longer periods titan A. gambiae larvae. It was generally concluded that clays have 11 negative impact on the persistence of Bti toxicity against mosquito larvae and th at such impact is more significant in mixtures containing large concentrations clay. It was also concluded that despite the environmental friendliness of Bti, its applicability by communities is limited in view of its short persistence when it is adsorbed to tropical soils which are found in most natural mosquito breeding sites.