EFFECTS OF CHELATED ZINC, SOLUBLE AND COATED FERTILIZERS, ON SOIL ZINC STATUS AND ZINC NUTRITION OF MAIZE

Maize (Zea mays L.) was greenhouse cultivated with doses of 5, 10, and 15 ppm of zinc (Zn) in order to test the effectiveness of laboratory- prepared coated and uncoated Zn fertilizers with commercial Zn-EDTA an d Zn-lignosulphonate (LS). Large increases were achieved both in crop yield and in Zn uptake in all cases while a large part of the Zn appli ed remained in the soil in easily plant-available forms. Positive sign ificant correlations were obtained between available Zn and the first three sequentially extracted fractions (water soluble plus exchangeabl e, organically complexed and that associated to amorphous sesquioxides ) and also between the variables, yield, Zn concentration, and plant Z n uptake. Zinc uptake by the maize plants can be fairly accurately pre dicted from its sequential fractioning in the soil using an equation o btained by multiple regression analysis. Consideration of the amounts of Zn remaining as available (DTPA extractable) in the soil and result s of a plant analysis let us conclude that under the conditions of our tests, Zn-EDTA is a better Zn source than Zn-LS. In addition, coating of Zn-EDTA products with rosin improves their performance.