Masters Dissertations

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Browsing Masters Dissertations by Subject "Acacia"

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    A study of accasia albida del. with reference to community afforestation
    (University of Dar es Salaam, 1983) Kiriinya, C. K
    Acacia albida Del. is a large nitrogen fixing leguminous tree typical of riverine sites in semi arid areas throughout Africa. This study is concerned with evaluating its potential for agroforestry. Laboratory, nursery and field experiments were carried out at Morogoro, Tanzania, to investigate seed pretreatment procedures, nursery growth and establishment, early field performance, nitrogen fixation rates and initial relationships with intercropped food crops. The most effective seed pretreatment was concentrated sulphuric acid for 20 - 30 minutes which gave 97 -100% germ nat on in 21 days while the least effective pre-treatment eras scorching which resulted in no germination over the same time. In the nursery, survival percentage was 98% and shoot growth was rapid: plant were 28.2 ± 6.7 cm tall, with mean biomass 4.6 ± 3,.6 g dry weight, after 12 weeks. Size at outlanting had no effect on survival, in the field: the mean survival percentage after months was 92% Large (43 cm}, medium (34 cm) and total increment of 10.4, 11.1 and 10.4 cm, respectively, over 6 months. Survival was affected by pre-out planting time in the nursery. The youngest (75 days higher mortality (13%) than older seedlings (11%) but the difference was not statistically significant. The mean height increment was 10.6 + 0.5cm and did not differ significantly among the different ages. Intercropping with maize was found not to affect young A, albida trees in height growth or root collar area increment the six months period. Conversely, maize yield was not affected by the presence of young A. Albida trees. Nitrogen fixation was detected in both nursery stock and field stock. The mean fixation rate recorded per gram dry weight of nodules in the nursery was 21 +11.6 n molC2 H4 mg -1 h-1 while in the field the rate was 10±5.5 n mol C2 H4 mg -1 h-1. Results are interpreted and discussed with respect to published information on the species and its use at Morogoro since 1980 in agroforestry experiments. It is concluded that A. albida has high potential for agro-forestry in semi-arid areas particularly since it is in such areas that pastoralism has major significance and is, in settled societies, complemented by rainy season food crop cultivation. Acacia albida is more compatible with this type of tradition than any of the better known agroforestry trees and is also better adapted to the conditions involved than many others.