Saturday, 15 July 2006

Effects of Vermicompost, Urea and Zinc Sulfate on Zinc Fractions in a Calcareous Soil.

Adil Reyhani Tabar, Mohamad Ardalan, Najaf Ali Karimian, and Gholam Reza Savaghebi. Univ of Tehran, Karaj, Iran

Water-Soluble Zinc (Zn) fertilizers are rapidly converted to insoluble forms in Calcareous Soils resulting in lower efficiency of such fertilizers. Knowledge of distribution of applied Zn in such soils is necessary for understanding the fate of applied Zn fertilizers and finding ways to increase their efficiency. A factorial experiment and CRD design with two replicates was carried out to examine the influence of 3 levels of vermicompost(0,5 and 20 gm.Kg-1), 3 levels of N(0,60 and 120 mg.Kg-1 as urea) and 3 levels of Zn( 0,5 and 10 mg.Kg-1 as ZnSO4.7H2O) on the various fractions of soluble plus exchangeable (ZnEX2), Carbonate adsorbed (ZnCar), Organic matter Complexed (ZnOm) Manganese Oxide bound (ZnMnox), Amorphous iron Oxide bound (ZnAFeOX). Crystalline oxide associated (ZnCFeOX), and residual (ZnRES) Zinc in a Calcareous Soil (Termic Calciorthids). Application of Urea at rate of 120 mg N. Kg-1 had no significant effect on Zinc fractions. Vermicompost increased the ZnEx2 and ZnOm. Application of ZnSO4, while significantly increased the Concentration of all forms of Zn, had a pronounced effect on Zn-RES. Overall conclusion was that 43-50% of the applied ZnSO4 was converted to residual form. It was also concluded that conversion of applied ZnSO4 to residual form was mainly responsible for retention of this fertilizer in calcareous soil. A significant correlation was also observed between zinc forms, themselves, which is presumably a reflection of the existence of a dynamic relation between the chemical forms of an element in soil. Keywords: Zinc forms, sequential extraction, calcareous soil, zinc sulfate, urea, vermicompost.

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