SOIL TESTING FOR PHOSPHORUS IN SOME NIGERIAN SOILS

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Abstract
Responses to P by potted maize (Zea mays) were determined in the greenhouse on soil samples taken from 68 locations in SE Nigeria and correlated with available P extracted by a selected chemical method. Responses to phosphate application were widespread. Dry matter yields were especially low in the acid sandy ferrallitic soils derived from sandstones and coastal plain sands, when no P was applied. An application of over 28 kg P/ha was needed in many cases to elicit a response. Soils from the lowland rain forest areas and soils derived from basement complex rocks gave higher dry matter yields and fewer responses to phosphate application than soils from the savanna areas and those derived from sedimentary rocks. Available P correlated positively with the percentage yield of maize (Zea mays) and the correlation coefficient, r = 0.648, was significant at the 0.1% level. Significant responses to phosphate application occurred when the percentage yield was below 55% and when available P content of the soil was less than 33.6 kg P/ha.