The Nyong basin is located in the lateritic domain. Soils are essentially ferrallitic: orthic modal soils on the South Cameroonian plateau with hydromorphic zones in the upper Nyong valley; yellow topomorphic soils in the coastal area.


The study of the pedologic cover in the Mengong catchment shows, over the granitoidic bedrock, two types of profile. (1) On the hills and their sides, the cover – whose thickness may reach 50 m in the highest points – gets progressively thinner towards the lower zones. Over the “classic” lateritic sequence (from bottom to top: saprolite, mottled clays, ferricrete disaggregating into nodules at the upper and the lower part of the slope), a very homogeneous sandy-clayey horizon, yellowish to reddish in colour, can be systematically observed; the origin of this superficial formation, locally very thick (up to 3 m on the hills) and whose contact with the underlaying ferruginous nodular horizon always appears clearly, has not yet been explained. (2) In the swampy depression, the lateritic sequence seems to be truncated: the saprolite, or the mottled clays, are overlaid by a whitish clayey-sandy horizon, considered as colluvial. It is overlapped by a greyish clearly hydromorphic horizon, 0.5 to 1.5 m thick, essentially constituted by kaolinite and residual quartz grains; local composition or colour variations – especially due to high organic matter contents – are observed in some lenses. At the top of this generally waterlogged profile, a dark 0.2-0.5 m thick fringe corresponds to an enrichment in organic matter, which represents sometimes more than 10% of the clayey-sandy soil.