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What is Chelation?

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. 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.

EDTA chelation

Imagine a lobster’s claw made of carbon and hydrogen atoms holding an ion. The more bonds that form between the ion and the carbon atoms, the stronger the ion is held within the chelate. 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.

Many micronutrients are unavailable to plants in their basic forms. This is typically due to the fact that these metals, such as iron, are positively charged. The pores or openings on the roots of the plant are negatively charged. As a result, the element can’t enter the plant due to the difference in charges. 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.

There are several chelating agents that are commonly used in commercial fertilizers. The chelating agent can be identified on the label beside the trace element it serves to make available to plants. If the label has EDTA written next to a trace element, the fertilizer contains ethylene-diamine-tetra-acetate, the most commonly used chelating agent. Higher quality grades of fertilizers may also contain DTPA (diethyle-netriamine-penta-acetate). EDDHA (ethylene-diamine-dihydroxy-phenylacetic-acid) represents the highest quality of synthetic chelating agents available and are the most effective across all growing environments.

EDTA is the most common chelating agent and is used for both soil and foliar applied nutrients. It has four points of connection. Like other synthetic chelates, EDTA is a foreign compound and is therefore not absorbed by the plant. When the chelated element is required, the plant will remove the element, for example iron, from the chelate and absorb the element. 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. 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.

DTPA is a chelating agent better suited for high pH conditions. It has five points of connection to the element it chelates, allowing it to hold the element more tightly. DTPA is more costly than EDTA and is less soluble so it is found in smaller quantities than EDTA in most synthetic fertilizer formulations.

Types of Chelating Agents and their Stability at Different pH Levels

The graph to the right shows the level of iron stability with different chelating agents at different pH levels. As you can see, EDDHA is the strongest chelate of any of the commonly used materials and maintains iron availability to plants past pH 9.0. However, other types of chelating agents can be used as long as pH conditions are suitable. EDTA is better suited to slightly lower than neutral pH levels. DTPA is most effective at slightly higher pH levels.

The strongest and therefore most effective of the synthetic chelating agents is EDDHA. It is found only in select fertilization formulations because of its relatively high cost.  House & Garden Nutrients uses EDDHA chelates to enable maximum absorption of their nutrients, making them the most unique and effective nutrient line on the market. Plants supplied with adequate levels of EDDHA are able to absorb more zinc than plants supplied with EDTA, which is very important as zinc is often locked out in the later part of flowering due to excessive phosphorous levels, causing plants to yellow.

There are also natural chelating agents available, such as fulvic acid, which is derived from the decomposition of organic matter. Unlike synthetic agents, fulvic acid can be absorbed into the plant, adding to the mobility of the nutrients within the plant. Fulvic acids can be most effective when the growing environment in the rhizosphere is above or below optimal. Even under adverse conditions, plants supplied with fulvic acid have been found to be remarkably free of signs of stress and deficiency.

For best results, use only high quality fulvic acid products such as Mad Farmer’s Nutrient Uptake Solution (N.U.T.S.). N.U.T.S. is sourced from ancient, organic humic shale, which is then extracted using only pure, cold water. This extraction process avoids the use of chemicals, heat, and pressure, which can destroy the quality of the fulvic compounds. N.U.T.S. is also UV filtered before bottling to ensure quality. N.U.T.S. can be added to the nutrient solution and/or used as a weekly foliar spray until one week prior to harvest.

To optimize growth in your garden, use several sources of chelation in your nutrient solution. This allows for more efficient nutrient absorption, transport, and other biochemical reactions. Look for nutrients that offer a range of chelating compounds, so that nutrients will be available through a wide range of conditions, including those above or below optimal. For increased results you may consider the addition of fulvic acid. When used properly, chelating agents can maximize nutrient uptake and increase photosynthetic response, greatly increasing plant performance and yields.

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