FOOD CROP YIELDS AND SOIL PROPERTIES UNDER POPULATION PRESSURE IN SUB-SAHARAN AFRICA - THE CASE OF CASSAVA IN SOUTHEAST NIGERIA

Cassava root yields in three villages in southeastern Nigeria with mar ked differences in population pressure were related to soil properties using various models. The soils of the low population village, being formed from a different parent material, were more fertile than those of the medium and high population villages and cassava root yields wer e significantly higher in this village. The specific soil properties w hich appeared to promote cassava yields included pH and contents of Mn , silt and sand, Absolute values of exchangeable Mg, Ca, acidity and e ffective cation exchange capacity, although not significantly correlat ed with root yield, were also most favourable in the low population vi llage. Thus inherent differences in soil properties rather than popula tion pressure may be the major factors contributing to variations in c assava root yields in these villages.