Chelate behaviour in saline-alkaline soil conditions

Summary A spectrophotometric method was used to study the effect of pH and competing ions (Ca, Mg, Na) on the stability of Fe- and Cu-chelates of EDTA, DTPA and EDDHA. The measured stability was compared with the calculated stability-pH diagrams. A favourable agreement with the values of the formation constants was observed. Laboratory and pot experiments were carried out by adding these chelates to saline-alkaline soil and the extractable fractions of trace elements in soil and their uptake by barley were evaluated. Availability and uptake of Fe and Cu significantly increased, with different magnitude, by chelate application. The influence on Mn and Zn was variable. The most effective chelating agents, as deduced from uptake were: EDDHA for Fe, Cu and Mn; and EDTA for Zn.Radiobiological and Physical chemistry, Faculty of Agricultural Sciences, Ghent Belgium