A study on the merits of separating tropical soils into groups and using different chemical extractants for different groups in the routine measurement of available soil phosphorus.

Abstract

Ten extractants were used for measuring the available phosphorus in 24 tropical soils, and the extractable P values were correlated against plant parameters obtained from a 170-day continuous cropping experiment and a 50-day response experiment. The Olsen method gave the highest correlations for the continuous cropping experiment and the Hislop resin method for the response experiment. When the 24 soils were separated into groups on the basis of organic carbon levels, soil classification or mineralogy, a higher set of correlation coefficients was obtained than when a single extractant was used for all the soils.