AbstractThe stability of Fe‐EDTA and Fe‐CDTA was investigated in order to evaluate their effectiveness under calcareous soil conditions. To accomplish this evaluation the reaction rate of fixation, K, the adsorption coefficient, Kd, and the retardation factor, S, of the iron chelate were determined through column experiments at pH 7.8 and two ionic strengths, I, of CaCl2.The results indicated that iron in Fe‐EDTA was more fixed than in Fe‐CDTA. The fixation increased by increasing the ionic strength. Also it increased linearly with increasing CaCO3content of the soil.The values of retardation factor, S, showed that this parameter depended more on the surface area of the soil than on I or CaCO3content. The product KS depends on CaCO3content, surface area of the soil, ionic strength and chelating agent used. It can be taken as an index for the efficiency of the iron chelate under different conditions.Fe‐EDTA was more adsorbed than Fe‐CDTA, the adsorption increased with increasing ionic strength and surface area