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Faidherbia albida Del. A. Chev. |
 
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Leguminosae
Faidherbia albida has a particular taxonomic position intermediate between the genus Acacia and the genus Inga. |
Author: Le Houérou
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Kad (Senegal), haraz (the Sudan), applering acacia, winter thorn. One of the largest of the Acacia trees in Africa reaching up to 25 m high in height and over 1 m dbh. As the elevation of the site increases its size becomes smaller (Tothill, 1954). Roots can reach aquifers up to 80 m below the surface. Young trees have inverted cone-shaped crown, old trees with a hemisperical large canopy. Young branches and twigs are cream coloured to whitish, stipular spines whitish, straight in axillary pairs, somewhat swollen at the base, up to 5 cm long, with a brown tip. Bark grey, rough, deeply fissurated and scaly with age. Slash pink to light brown and fibrous. Bipinnate leaves blue-green with 3-12 pairs of pinnae carrying, 6-23 pairs of leaflets up to 12 mm long x 5 mm wide, partly overlapping. Contrary to all other native "acacias" albida sheds its leaves in the rainy season and keeps them throughout the dry season, which is made possible by the fact that the species behaves as a phreatophyte. Other characteristics are the lack of glands on the petioles, but present between each pair of pinnae. Inflorescence in dense spikes 7-10 cm long x 1.5-2 cm wide, cream colored very fragrant. Pods quite typical bright orange to reddish-brown in colour 10-15cm long x 2-3 cm wide (hence the vernacular name of "apple-ring acacia"), containing 10-20 shining dark-brown seeds with a small charateristic tubercule. It remains leafless during the rains and assumes new foliage and flowers after the commencement of the dry season (Dalzeil, 1955). Commonly distributed on flood plains and banks of large rivers on alluvial soil, where it may occur in pure stands or as a constituent of riparian woodland (Wilson and Bredon, 1963). It is tolerant to frost, unlike many Sahel species. In Senegal, its distribution strikingly coincides with the isopiezometric line of 80 m of maximum depth of aquifers, which suggests it can reach water down to that depth, but it also occurs in the rice fields of Casamance under 1,500 mm of MAR with hydromorphic gley soils ; it is also present in the "koris" (=dry wadis) of the Aïr mountains under MAR of 50-100 mm. Throughout tropical Africa, from Egypt, Senegal and the Gambia south to the Transvaal and Natal, Syria, Palestine, India. In Africa, it is widely distributed from the dry valleys of the Sahara, the Negev and the Namib, throughout West, East and South Africa, only missing North of the Sahara and in the Congo Basin. It occurs up to elevations of 2,700 m (Jebel Marra). Propagation in the traditional agrosystems was done from naturally grown seedlings in millet fields, selected and nurtured by the farmers until they reach a size above the reach of livestock (0.5-0.8 m per year). Direct seeding of pregerminated seeds was very successful in Senegal (Cazet, 1987, 1988; Cazet & Sadio, 1988) and should be encouraged for its low cost, and therefore sustainability. But direct seeding has also a constraint as it requires a careful weeding in the young stages of establishment, to avoid competition for water. Land fertility : it has been shown than millet yields under Faidherbia are, on average, 2.5 times higher than away from the trees (Charreau & Vidal, 1965 ; Dancette & Poulain, 1969 ; Radwanski & Wickens, 1967), detailed studies of water and nutrient balance and turnover fully explained this effect. The similar system with millet-Prosopis cineraria in Rajasthan (India) produced similar results (Mann & Saxena, 1980 ; Mann & Shankaranayan, 1980). The wood, soft and of medium quality is used as timber, handicraft, various tools, fuel and charcoal. Boudet (1970) suggested that it be planted as a windbreak in West Africa and lopped in the dry season for livestock feed. Charreau and Vidal (1965) state that the fertility-building ability of F. albida has long been known in Senegal and that populations of the trees are protected and may reach a density of 40 to 50 trees/ha. From mineralization of leaf drop and nodulation there is a marked increase in fertility from the dripring of the tree to the trunk, particularly in nitrogen, phosphorus and exchangeable calcium. Millet (Pennisetum typhoides) yields are multiplied 2.5 times and protein content by a factor of 3 or 4 near the trees. Annual accession of fertility per 150 m2 has been calculated as 183 kg. CaO, 39 kg. MgO, 19 kg. K2O, 75 kg. N, 27 kg. P2O5 and 20 kg. S. Other uses : the bark contains 20-25 % tannins, wood ashes are used for making soap, seeds are eaten in time of dearth. Medicinal uses are : febrifuge, haemorraghe, cough, pneumonia, kidney disorders, vomiting, diarrhoea, postpartum complications, psychological disorders, ophtalmia, rheumatisms, heart tonic. It has played an important rôle in the development of centuries-old agrarian civilizations in large parts of the African continent. Nutritional Quality and Animal Production It produces a large number of twisted pods which are relished by camels, cattle and game animals. The pods are indehiscent, and Lamprey (1967) believes that passage through the animal is necessary to stimulate germination. Forage production is ca 20-30 kg per tree per annum either from lopped foliage or from pods, (it must be the one or the other, one cannot get both on the same tree), which for a density of 25 trees per hectare corresponds with 500-750 kg DM ha yr-1 , i.e. the full ration of 1 to 1.5 sheep per hectare per annum , i.e. 40 to 60 kg lwt/ha/yr (whilst the optimum stocking rate in the Sahel rangelands is ca 25 kg lwt/ha/yr), at the same time the sytem allows for an additional production of 1,220 to 1,500 kg of millet grain, and 2,500 -3,000 of stalks.
Aubréville 1950 ; Brenan 1957a ; Brenan 1959 ; Catinot 1967 ; Berhaut 1975 ; Giffard 1964 ; Giffard 1971 ; Giffard 1974a ; Giffard 1974b ; Charreeau & Vidal 1965 ; Dancette & Poulain 1968 ; Wickens 1969 ; Weber et al. 1977 ; Felker 1979 ; Von Maydell 1983/86 ; Baumer 1983 ; Le Houérou 1980a ; Le Houérou 1980c ; Geerling 1982/88 ; CTFT 1988 ; CTFT 1996 ; Fagg 1992 ; Vandenbelt 1992 ; Burkill 1995 ; Wickens et al. 1995 ; Dommergues & al. 1999. |
