Chemistry, clay activity and mineralogy of soils along three toposequences over igneous and sedimentary lithologies in Southeastern Nigeria
1995
Eshett, E.T. (Federal University of Technology, Owerri (Nigeria). School or Agriculture and Agricultural Technology)
Soils of 3 toposequences in Northern Cross River State of Nigeria, derived variously from granite, sandstone, shale, and basalt, were examined and characterized in terms of morphology-physico-chemical properties, clay activity, and minerals present in the clay fraction. An attempt was made to investigate and establish any possible links or relationships between the drainage condition, the dominant clay mineralogy and the other inherent soil chemical characteristics which could help in the proper management of these soils. The well-drained upland pedons (coarse, loamy, mixed, isohyperthermic typic paleudults) had low pH values, low effective cation exchange capacity, and low clay activity. These characteristics were attributed to the good drainage condition and the associated mineral assemblage which consisted of kaolinite (predominant) and some hydrous oxide clays (goethite and gibbsite). Mineral hydromorphic soils, occurring in valley bottom sites, contained smectite which accounted for higher effective cation exchange capacity and clay activity. Poor to imperfect drainage condition prevailing in the latter, coupled with higher pH and higher base supplies, favoured in situ synthesis of smectite and conveyed generally higher agricultural potentials on the hydromorphic soils.
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