SEQUENTIAL SELECTIVE DISSOLUTION OF IRON, ALUMINUM, AND SILICON FROM SOILS

The series of reagents, Pyrophosphate, oxalate, and dithionite have be en applied sequentially in the characterisation of a group of podzolic soils and the cumulative amount of iron (Fe), aluminium (Al), and sil icon (Si) extracted has been compared with the amounts removed when th e reagents are used separately on different aliquots of the same soils . For Fe, the results demonstrate clearly that the reagents when used sequentially in the order pyrophosphate, oxalate, dithionite extract f ractions which are subsets of each other. On the other hand, foe Al an d Si the order of effectiveness of the reagents does not follow the sa me sequence, thus limiting the effectiveness of the approach to Fe alo ne.