It has five points of connection to the element it chelates, allowing it to hold the element more tightly. EDTA is better suited to slightly lower than neutral pH levels, as high pH conditions will cause it to release the element back into the nutrient solution instead.ĭTPA is a chelating agent better suited for high pH conditions.
However, since the chelating agent is foreign to the plant, it will give up the chelating agent (EDTA) back into solution where it is free to chelate other elements. When the chelated element is required, the plant will remove the element, for example iron, from the chelate and absorb the element. Like other synthetic chelates, EDTA is a foreign compound and is therefore not absorbed by the plant. EDDHA ( ethylene-diamine-dihydroxy-phenylacetic-acid) represents the highest quality of synthetic chelating agents available and are the most effective across all growing environments.ĮDTA is the most common chelating agent and is used for both soil and foliar applied nutrients. Higher quality grades of fertilizers may also contain DTPA ( diethyle-netriamine-penta-acetate).
If the label has EDTA written next to a trace element, the fertilizer contains ethylene-diamine-tetra-acetate, the most commonly used chelating agent. The chelating agent can be identified on the label beside the trace element it serves to make available to plants. There are several chelating agents that are commonly used in commercial fertilizers. However, if a chelate is added, it surrounds the metal/mineral ion and changes the charge into a neutral or slightly negative charge, allowing the element to easily pass across the cell membrane and travel into the plant. As a result, the element can’t enter the plant due to the difference in charges. The pores or openings on the roots of the plant are negatively charged.
This is typically due to the fact that these metals, such as iron, are positively charged. Many micronutrients are unavailable to plants in their basic forms.
The strength of the chelate’s hold on the ion determines, as pH increases, how long the element will continue to be available to plants. The more bonds that form between the ion and the carbon atoms, the stronger the ion is held within the chelate. Imagine a lobster’s claw made of carbon and hydrogen atoms holding an ion. Chelation occurs when certain large molecules form multiple bonds with a micronutrient, protecting it from reacting with other elements in the nutrient solution and increasing its availability to the plant. The word chelate (pronounced: “key-late”) is derived from the Greek word “chele” which literally means “claw”, a rather fitting association because chelation is a process somewhat like grasping and holding something with a claw.