Effect of excess chelating agent in nutrient solution at low levels of iron, zinc, copper and manganese

Abstract

When iron was supplied as FeEDDHA at 10^‐6 M or 10^‐7 M, Mn and Zn as sulfates variously at 10^‐5to 10^‐7 M and Cu at 10^‐6 M, the copper concentrations of trifoliate leaves of bush beans (Phaseolus vulgaris L.) was in the toxic range (30–77 mg/kg)/ when iron was at 10^‐5 M with the same concentrations of zinc, manganese and copper as above, the copper was in the adequate range (7.5–14 mg/kg) but when 10^‐4 M Na₂EDTA was applied to each of the above solutions, copper in the leaves was in the deficient range (2–4 mgAg) • The results point to the need for extreme care when chelating agents are used in hydroponic nutrient solutions especially where copper, manganese and/or zinc as well as iron are applied in che— lated form. As iron becomes depleted in a nutrient solution, copper toxicity can result, but deficiency can also result if there is excess free chelate even with the same copper level in the nutrient solution. The multielement stresses were shown to be mostly additive in nature, although in some cases they seemed to be synergistic.