Effect of Various Levels, Sources of Zn and Zn Solubilizing Bacteria on Zinc Transformation in Calcareous Soil

Intensive cultivation with high yielding varieties and imbalanced fertilization using high analysis fertilizers resulted in increasing micronutrient deficiencies in soil. Zinc is one among the micronutrients essential for the growth and development of crops. Application of inorganic zinc fertilizers to mitigate Zn deficiency is relatively ineffective since it gets converted into unavailable forms. To study the Zn transformation in calcareous soil as influenced by various levels, sources of Zn and Zn solubilizing bacteria, an incubation experiment was carried out. Distribution of Zn fractions in the soil at harvest stage followed the order water soluble plus exchangeable (WS-Ex) < organically bound < carbonate bound < Fe-Mn oxide bound < residual Zn. Plant available forms of Zn viz., water soluble and exchangeable and organically bound Zn were significantly affected by the sources, levels of Zn and Zinc Solublising Bacteria (ZSB) application. Application of ZnSO4 at 7.5 kg Zn ha-1 along with ZSB registered high WS-Ex. and Org. Zn. Lower carbonate bound Zn fraction was observed with ZSB application when compared to the treatments without ZSB application. Fe-Mn oxide bound fraction of Zn was also significantly influenced by the sources, levels of Zn and ZSB application. Sources of Zn and ZSB application did not have significant influence on residual and total Zn. With increasing levels of Zn significant increase in all the Zn fractions and total Zn were observed and the highest value being recorded with 7.5 kg Zn ha-1.