Zinc speciation in phosphate‐affected soils

Zinc (Zn) speciation was determined in a Zn pre‐treated Andosol, Inceptisol, and a Vertisol before and after adding phosphate. The fractions obtained, i.e., soluble, exchangeable, iron‐manganese (Fe‐Mn) bound, chelated and insoluble organic forms had a different distribution in the three soils. The exchangeable form predominated in the Andosol, followed by Fe‐Mn oxide bound Zn and minor amounts of the chelated forms, whereas Fe‐Mn oxide bound Zn was very abundant in the Inceptisol and Vertisol. Sizable amounts of the exchangeable form were also present. Phosphate pre‐treatment of the Inceptisol and Vertisol did not alter the distribution of the different forms of Zn, whereas in the Andosol the exchangeable as well as the Fe‐Mn oxide bound Zn increased markedly, chelated Zn also increased somewhat.