Preliminary Evaluation of Different Chemical Soil Test Methods for Available Phosphorus through Correlation with Greenhouse Test1

Abstract

Chemical methods for determination of the “easily soluble” or “available” fraction of soil phosphorus are numerous. Determinations of this kind are empirical since the fractions determined are in no way the estimates of any definite of the soil phosphorus actually available to the plant. Consequently there is no general agreement on methods with regard to magnitude of the “available” P extracted as well as the degree of correlation with the actual P taken up by the crop. However, methods that show high degree of correlation with the results of field experiments can be used to interpret the actual phosphorus status of the soils studies. There are a large number of phosphorus soil test methods proposed for the estimation of the phosphorus status of the soil, each of which may be suitable for particular soils at different locations. In order to correlate and calibrate P soil test methods with the field experiments, preliminary studies concering the practical convenience of the methods, as well as their relation to phosphorus taken up by the crops, should be carried out in order to select those methods which show promise of being of practical value.