Response of maize to soil applied ZnSO4 and ZnEDTA

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 mays L. 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.