Much of Uganda lies on a raised plateau between the western and eastern African rift valleys, characterized by basement complex rocks, granites, gneisses, and schists of the pre-Cam-brian age. The rocks have been subjected to differential weathering. According to past surveys, a total of 138 soil units were recognized. For the purpose of this study focus is placed on soils of the agroclimatic zones. Humid montane agroclimatic zone (Mt. Elgon and Mt. Muhavura) soils are derived from volcanic ash and agglomerate; they can be classified as Ando-sols and vary along the landscape depending on altitude. Their textural class is predominantly clay. These soils are generally rich in organic matter. Soils in the subhumid agro-climatic zone are highly weathered and are variable but often have high clay content grouped under sandy clay loams (Lufafa et al., 2003). The soils are acidic with moderate levels of organic matter. In the semi-arid environment soils are of lacustrine origin and vary along the landscape. They are predominantly sandy with low levels of organic matter and largely classified as Acrisols and Ferralsols (Figure 20.2). In general, the soil organic carbon across the agroclimatic zones is closely related to land use (Table 20.2).

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