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University of Dar es Salaam (1983)

A study of Acacia albida Del. with reference to community afforestation

Kiriinya, C K

Titre : A study of Acacia albida Del. with reference to community afforestation

Auteur : Kiriinya, C K

Université de soutenance : University of Dar es Salaam,Tanzania

Grade : MSc 1983

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 mvestigate seed pre-treatment 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% germination in 21 days, while the least effective treatment was scorching which resulted in no germination over the same time. The nursery, survival percentage was 98% and shoot growth was rapid : plants were 28.2 ? 6.7 cm tall, with mean biomass 4.6 ? 3.6 g dry weight after 12 weeks. Size at outplanting had no effect on survival in the field. Mean survival percentage after 6 months was 92%. Large (43 cm), medium (34 cm) and small (26 cm) seedlings all grew in height at the same rate in the field (10.6 ? 0.45 cm over 6 months). Survival was affected by pre-outplanting time in the nursery. The youngest seedlings (75 days old) suffered higher mortality (13%) than older seedlings (11 %). The mean height increment was 12.4 ? 0.95cm and did not differ significantly among the different ages. Intercropping with maize was found not to affect young A. albida trees in height growth increment or root collar area increment. Conversely, maize yield was not affected by the presence of young A. albida trees. Nitrogen fixation was detected in both nursery stock and fieldstock. The mean fixation rate recorded per gram dry weight of nodules in the nursery was 21 ? 11.6 n mol. C2 H4 mg’ h’ while in the field the rate was 10 ? 5.5 mol C2 H4 mg’ h’. 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 agroforestry in semi-arid areas, particularly since it is in such areas that pastoralism has major significance and 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.

Mots clés : Afforestation / Acacia /Community afforestation / Afforestation / Legouminous trees / Nitrogen fixation / Agroforestry / Tanzania /Morogoro

Présentation (Research Kenya)

Page publiée le 23 septembre 2010, mise à jour le 14 février 2018