Use of synthetic chelating agents in experimental and commercial nutrient solutions

Abstract

FeEDDHA is not a good source of iron for monocots in nutrient solutions (hydroponics) and FeDTPA also is not as good as FeEDTA for monocots. Combinations of FeEDDHA and FeEDTA may be better than either alone. Excess EDTA and DTPA can inhibit uptake of zinc and copper although chelated zinc and copper appear to be available to a wide variety of plants. They also can inhibit uptake of iron when present in excess because they effectively chelate Fe⁺⁺ while EDDHA does not. The procedure then of having all iron, zinc, manganese and copper in a chelated form in a nutrient solution appears to be satisfactory so long as there is not a large excess of chelating agent. FeEDDHA (and FeDTPA to some extent) under some conditions can induce manganese, zinc and copper deficiencies but this will not be the case if the nutrient solution is carefully formulated to have these four micronutrients in concentration and balance related to their needs by plants and in relationship with the nitrogen, phosphorus and potassium. Stability of Fe⁺⁺ is EDDHA < EDTA < DTPA < CDTA which gives FeEDDHA advantage in nutrient solutions.