Abstract: The invention relates to the process for the preparation of iron(III) chelates of N,N?-di(2-hydroxybenzyl)ethylenediamine-N,N?-diacetic acid and its derivatives of the formula (I) wherein both R substituents have the same meaning and represent H, C1-C4 alkyl, CH2OH, SO3M or COOM, and M is a sodium, potassium or ammonium cation, wherein the aqueous solution of a corresponding chelating agent is contacted with metallic iron by the circulation of said aqueous solution through the bed of pieces of metallic iron in a flow reactor while simultaneously blowing air or oxygen through the aqueous solution of the chelating agent in the flow reactor, optionally in the presence of a hydrogen peroxide solution. Chelates of the formula (I) are useful as the components of plant fertilizers.