Department of Plant Sciences

The low solubility of the iron, manganese and zinc oxides in the pH range of calcareous soils contributes, among other factors, to the low availability of these nutrients to plants. The aim of this work was study the efficacy of the application of Fe, Mn, Zn and Cu chelates to correct the deficiencies in soybean in hydroponic solution in the presence of CaCO3. Fe was applied as o,oEDDHA/Fe3+ in all the cases while Mn, Zn and Cu were applied as o,pEDDHA, EDDS, EDTA, HEDTA or DTPA chelates, with the same chelating agent for the three metals in the same treatment and two additional treatments with Mn and Cu chelated by EDTA and Zn chelated by o,pEDDHA or EDDS. Three controls with no Mn, no Zn and no Mn and Zn with the others chelated by EDTA were tested too. Results indicate that the content of Fe in leaf was similar in all the treatments due the same chelated was applied. The treatments that presented the higher levels for Mn and Zn in leaf, especially for Zn, was the one with the application of Mn and Zn as o,pEDDHA. The higher level for Cu was produced in the treatment with EDTA. It seems that the less stable phenolic chelates for Mn and Zn, like o,pEDDHA, are adequate for the nutrition of Mn and Zn in hydroponics due the low competence of this chelating agent with the plant for the metals.