Effect of continuous maize-cropping on yield,organic carbon mineralization and phosphorus supply of savannah soils in western Nigeria

Summary Sixty surface soils collected from major soil classes in the western Nigeria savannah were cropped to maize 6 times in succession without P fertilization. Dry matter yields, %P and P uptake decreased significantly until the sixth cropping. Organic matter decreased with cropping but no significant loss in total P was recorded. Inorganic P and saloid-bound P decreased, while organic P, Al-P, Ca-P and Fe-P increased. All the changes had little or no relationship with yield and P uptake while contributions from saloid-bound and Al-P utilization by maize were indicated. Bray's P₁ available P decreased until the fourth cropping, but increased afterwards. The increase notwithstanding, lower correlations were obtained with yield and P uptake of the succeeding crops.