Response of maize to soil applied ZnSO4 and ZnEDTA

Abstract

In this study the fertilizing effect of ZnEDTA (zinc ethylenediaminetetraacetate), and ZnSO₄ּ 7H₂O (ZnSO₄ּ) (zinc sulphate heptahydrate) was compared on calcareous loam soil. A pot experiment was set up with maize (Zea maysL. var. ‘P37N01’). Plants were treated with basic NPK doses and with Zn at increasing rates: 0, 2.5, 5.0 and 10 mg kg^-1 Zn in ZnEDTA and in ZnSO₄ form, respectively. The ZnEDTA and ZnSO₄ treatments increased the dry matter production compared to control by an average of 16%. Applying 2.5 mg kg^-1 Zn, shoot Zn uptake was 1.3-fold greater by plants treated with ZnEDTA, than that of treated with ZnSO₄. In the case of higher rates (5.0 mg kg^-1 Zn and 10 mg kg^-1 Zn), Zn uptake from ZnEDTA was approximately twice as much as that of ZnSO₄. This result confirms that ZnEDTA as Zn complex is more effective than ZnSO₄ on calcareous soil. The increasing ZnEDTA and ZnSO₄ doses enhanced the soil’s initial diethylenetriaminepentaacetic acid (DTPA) Zn concentration to 1.8, 3.0, 6.3 mg kg^-1 and 1.9, 3.5, and 6.5 mg kg^-1, respectively. Contrary to our expectations, DTPA soil extractant was not able to indicate the difference in Zn availability between soils treated with ZnEDTA and ZnSO₄. During the experiment, 0.6-1.7% of the added Zn doses were absorbed by the plants, and 48-59% of it could be measured back in the form of DTPA-Zn for both Zn fertilizers, the other half of the added Zn presumably converted to less available Zn forms.