Effect of Continuous Cropping and Fertilization on Zinc Fractions and their Contribution to Plant Uptake under Rice-Wheat System

Abstract

The effect of continuous cropping and fertilization on Zn fractions in soil and their relation with Zn uptake in rice-wheat system was studied in an Aquic Hapludoll of the G.B. Pant University of Agriculture and Technology, Pantnagar, Uttarakhand during 2004–2005. Application of 100% recommended dose of NPK + Zn increased the ammonium acetate-extractable, HCl-extractable, residual and total Zn in the soil. Combined use of 100% NPK + FYM resulted in highest content of copper acetate-extractable as well as pyrophosphate-extractable Zn while the highest content of CBD-extractable Zn was found in the unfertilized fallow soil. All soil Zn fractions except CBD-extractable Zn, were significantly correlated among themselves indicating existence of a dynamic equilibrium with each other. Zinc uptake by rice-wheat was improved with conjoint use of 100% NPK and FYM. The most important chemical fraction of soil Zn with respect to the crop uptake was the HCI-extractable Zn.