Zinc chelate reactions in alkaline soils

Abstract

The changes in the distribution of competing metal ions during the reaction of Zn-EDTA (ethylenediamine tetraacetic acid), Zn-DTPA (diethylenetriamine pentaacetic acid) and Zn-FA (fulvic acid) with alkaline soils for periods ranging between 1 and 30 days were determined by monitoring the concentrations of complexed zinc, iron, manganese, copper, and calcium in the supernatant soil solution. The reactions of Zn-EDTA and &-FA were mainly influenced by pH of the soil suspension and the aqueous calcium concentration. The reaction of Zn-DTPA in these soils was also influenced by the release of labile iron, manganese, and copper from the solid matrix into the ambient solution. There was an initial fast decrease in the concentration of soluble zinc in the solution, followed by a slower rate of decrease. The initial fast reaction conformed to a first-order reaction kinetics. The implications of metal cation interaction during the reaction of zinc chelates with alkaline soils in the micronutrient nutrition of crops are indicated.