Characterization of a weathering sequence of soils derived from volcanic ash in Cameroon. Taxonomic, mineralogical and agronomic implications

Abstract

The characteristics of eight pedons developed in Quaternary basaltic pyroclasts in Western Cameroon under humid tropical conditions are reported. The soil weathering sequence consists of an Andept-Tropept-Udalf-Udult association. Andic properties, physico-chemical characteristics and weathering stage clearly distinguish the taxonomic units. The total reserve in bases (TRB) and the clay content measured after adequate H2O dispersion with Na+-resins both appear to be suitable weathering indices. Clay mineralogy of non andic soils shows direct relationships between interstratified halloysite-smectite content, CEC of the clay fraction and weathering stage. The weathering stage of the investigated soils is reflected not only in their components and classification, but also in their nutrient status and banana crop performance. © 1989.