EDAPHIC COMPONENT OF THE ENVIRONMENTAL DEGRADATION RESULTING FROM THE REPLACEMENT OF TROPICAL RAIN FOREST BY FIELD AND TREE CROPS IN SW NIGERIA

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Abstract
Mature tropical rain forest is in a state of dynamic equilibrium with its soil, micro-and macro-climate. Data collected in the cocoa producing areas of SW Nigeria show that when this forest is removed and replaced by field or tree crops, the balance between vegetation and soil breaks down, and this leads to instability and a considerable deterioration in soil quality. An index of soil deterioration was derived and showed the following percentage declines for field and tree crops respectively: bulk density, 28% and 31%; total porosity, 12% and 18%; pH, 16% and 13%; organic matter, 29% and 26%; nitrate nitrogen, 35% and 27%; available phosphorus, 19% and 19%; calcium, 24% and 41%; sodium, 50%, 50%; potassium, 27%, 43%; magnesium, 36%, 47%; cation exchange capacity, 36%, 34%; base saturation, 5.4%, 8.7%. This study is one of the first attempts to assess soil deterioration on peasant farmers' cocoa plots.