Application of ZnSO4 or Zn-EDTA fertilizer to a calcareous soil: Zn diffusion in soil and its uptake by wheat plants

BACKGROUND: The objective of this study was to compare the efficiency of two Zn sources and two application methods on (i) Zn diffusion from fertilized soil to unfertilized soil, (ii) grain Zn concentration and (iii) grain Zn bio-accessibility to humans. In the laboratory experiment, 20mg ZnSO4 or 4mg Zn-EDTA were applied to a 5mm and 1 mm-wide space in the soil in the half-cell technique. In the greenhouse experiment, Zn-ZnSO4 or Zn-ethylenediaminetetraacetic acid (Zn-EDTA) wasmixed or banded with the soil at a rate of 20 or 4mg Zn kg(-1), respectively. RESULTS: The results from the diffusion experiment showed that both the extractability and the diffusion coefficient of Zn were higher when Zn fertilizer was applied to a 1 mm-wide space than when it was applied to a 5 mm-wide space. Zn-EDTA had a greater diffusion distance than ZnSO4. The greenhouse experiment showed that the mixed ZnSO4 application and the Zn-EDTA application (both mixed and banded) treatments significantly increased grain Zn concentration and bio-accessibility. The positive effect of Zn-EDTA on grain Zn concentrations and bio-accessibility was greater than that of ZnSO4. The banded application reduced the effectiveness of ZnSO4 but not of Zn-EDTA. CONCLUSION: It was concluded that Zn-EDTA was a better Zn source than ZnSO4 for increasing grain Zn content in a potentially Zn-deficient calcareous soil. (C) 2015 Society of Chemical Industry