[en] Landscape Ecological Survey of the Bipindi-Akom II ... - ITTO

5. SOILS
5.1 LITERATURE REVIEW
The' Atlas du Cameroun' (1 :2,000,000) and the 'Carte Pedologique du Cameroun Oriental'
(1: (1:1,000,000) 1 ,000,000) provide information on the soils in the TCP research area. The scales of these soil
maps differ greatly from this reconnaissance inventory (1: 100,000). These maps with their
explanatory notes (Segalen, 1957; Martin and Segalen, 1966), together with the' Atlas Regional,
Sud-ouest I' by Franqueville (1973) give a good indication of the main soils of Southwest
Cameroon. The three main soil types of Southwest Cameroon, according to the above mentioned
studies, are are' 'les les sols ferrallitiques jaunes sur roches acides (gneiss)', 'les sols ferrallitiques
rouges sur roches acides' and 'les sols alluviaux' (see also section 2.6).
According to the' Atlas du Sud Cameroon, scale 1 :500,000 (MINREST and ORSTOM, 1995),
the'sols ferralitiques fortement desaturees typiques jaunes ou rajeuni jaunes cl ocres' and 'les
sols peu evolues ou bruts' are found around the city of Ebolowa east of the TCP study area.
South of the line Ebemvok and Akom 11, a detailed soil study of 65 hectares has been carried
out by Roubain who paid special attention to the genesis of soils. He reports that well drained
yellowish brown clay soils dominate on gneisses, whereas the reddish brown soils occur on
basaltic rocks. Laterite banks are exceptional in this region (ORSTOM - Roubain, pers. comm.,
1995).
Soil studies in the Mbalmayo area, situated northeast of the TCP research area, were carried out
on inventory scale by Yemefack and Moukam (1995) and on detailed scale by Ndjib (1987) and
Ngeh et al. (1995). The soils in this area have been developed on (mica)schists, gneisses and
granites of Precambrian age. Yemefack and Moukam (1995) classify the dominating well
drained yellowish brown clay soils as Xanthic Ferralsols (low cation exchange capacity, low
base saturation) with or without textural differentiation.
Ndjib (1987) differentiates the strongly weathered soils on the basis of texture, coarse fragment
content and colour. He relates these differences to parent material (soils on schists have more
coarse fragments than the ones on gneiss) and physiographic positions (development of argic
properties on top positions and mid-slopes).
Bilong (1992) reports that around Akongo, which is also east of the TCP research area, well
drained yellowish brown clay soils are formed on all kinds of parent materials. He relates the
yellowish colour to goethite, an iron hydroxide. hydroxide. Goethite, which can be formed under a soil
climate climate with with sufficient moisture in the dry seasons, gives a yellowish brown colour to the soil
(Bilong, 1992).
According to Touber (1993b) the soils in the TCP research are remarkably uniform throughout
the area. They are well to moderately well drained, very deep, yellowish brown clay loams to
light clays. Variations in depth, internal drainage, texture and gravel content occur. Some
patches of redder soils may occur and an altogether different soil type is found in the valleys.
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