Transformation and Availability of Applied Zinc to Maize in Calcareous Soil

A greenhouse experiment was conducted to study transformation and availability of applied zinc in calcareous soil treated with zinc sulphate and zinc fulvate (Zn-FA). The appliCation of varying levels of zinc through zinc fulvate augmented dry matter yield, zinc uptake and per cent zinc derived from fertilizer more than that from zinc sulphate. The relative amount of zinc in various fractions and the relative distribution of applied 65Zn in these fractions at 25 days of maize growth were in the order: CBD-extractable Zn > organically bound Zn > comp/exed Zn > water soluble + exchangeable Zn > HCI soluble Zn. Different fractions of zinc increased with increasing levels of zinc. However, the distribution of applied ⁶⁵Zn in the treatment of zinc fulvate was greater than that of zinc sulphate. Organically bound Zn was correlated significantly with zinc content in soil treated with Zn-FA (Zn-FA, r = 0.689 **). The path coefficient and step down regression analysis show that complexedZn is the major source of zinc availability to maize in calcareous soils treated with Zn-FA and HCl extractable Zn and CBD-extractable Zn are important in soil treated with ZnSO₄. Simultaneously the availability of Zn from all chemical pools in soils, directly and indirectly, has been decreased through strong bonding with stable organic complexes.