THE AGING OF PHOSPHORUS IN SOME HUMID TROPICAL SOILS OF NIGERIA: 2. THE EFFECT OF AGING PHOSPHORUS IN SOME SOILS OF SOUTHEASTERN NIGERIA ON THE RESIDUAL PHOSPHORUS FRACTIONS IN THE SOIL AFTER CROPPING

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Abstract

ABSTRACT

Ten acid, humid, tropical soils of southeastern Nigeria, which received phosphate and lime treatments, were subjected to phosphate fractionation analysis after three crops of maize had been grown on them.

The bulk of the applied P remaining in the soil after cropping had reverted to aluminum and iron phosphates. These two P fractions were highly significantly correlated with the P-sorption capacity of the soils (r = 0.874 and 0.933, respectively). Calcium and organic P were not significantly affected by the treatments.

Although the quantity of sorbed P remaining in the soil after cropping increased with increasing P-sorption capacity, the amount of this residual P that was extractable with anion exchange resin decreased with it. Aging of P in the soil before cropping had no effect, either on the residual P fractions left in the soil after cropping or on thier solubility.

Liming generally increased the level of resin-extractable P in the soils, but did not have significant effects on the distribution of the various P fractions.

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