Chemically Extractable Zinc as Affected by Zinc Sources and CaCO₃ under Submerged Soil

The effects of CaCO₃ and forms of Zn on pH, redox potential and chemically extractable Zn were studied in laboratory under submerged soil conditions CaCO₃ was added to a non-calcareous Dharsul silty loam soil at the rate of 0, 4 and 8%(W/W) and Zn was applied as ZnSO₄, ZnO and Zn-EDTA at 0, 5 and 10 ppm. The pH was high in CaCO₃ treated samples and it was higher with Zn-EDTA than with ZnSO₄ and ZnO but Zn doses had no effect on pH. Redox potential remained higher in the beginning with addition of CaCO₃ and Zn but decreased with increase in time. The rate of decrease was faster when CaCO₃ or Zn was added.

The DTPA-extractable Zn decreased with increase in incubation time. The addition of CaCO₃ decreased and addition of Zn sources increased this form of Zn. Zn-EDTA gave always higher Zn content followed by ZnSO₄ and ZnO. However, ammonium acetate-extractable Zn increased after 1 week of incubation and then started decreasing. CaCO₃ decreased this form of Zn too, but among Zn sources, ZnSO₄ always gave highest Zn content followed by ZnO and Zn-EDTA. ZnO and Zn-EDTA, however, behaved almost similarly with respsct to ammonium acetate-extractable Zn.