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Microsource Minute

Chelation

 

Typing Chelation in Thesarus.com displays no results; if we could create the entry ourselves, the first synonym we’d enter is protection.  Chelation protects a micronutrient from undesirable reactions in fertilizer solutions and the soil. There are multiple types of chelating agents with different attributes, compatibilities and price points. Citric acid and EDTA are common, effective chelates found in our liquid micronutrients. Their mode-of-action is similar, but EDTA creates a stronger bond than citric.

How it Works

The word “chelate” is Latin for claw; the “claw-like” molecular structure encircles the positively charged cations (Zn2+, Mn2+, Fe2+, Cu2+). This converts the positively charged cations to negatively charged molecules. This negatively charged chelate molecule is then repelled by other negatively charged ions and the soil.

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Phosphate Reaction

Negatively charged phosphorus acts like a magnet attracting the positively charged micronutrient metals. This reaction, for example with zinc, creates a water insoluble Zinc Phosphate solution that is not plant available.

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Therefore, an EDTA chelate is required when mixing micronutrients with ortho-phosphates such as 3-18-18.  If a non-chelated micro is added, it will create a white pigment, milky solution not suitable for application. 

Key Considerations

  • Chelated micros are negatively charged and protected from tie-up in the soil making them more available for plant uptake.  However, this mobility means they are also more susceptible to leaching.  This is why chelated micros are commonly applied in smaller rates with starter fertilizer at planting.

  • EDTA chelate is the strongest most effective chelating agent, and its vast compatibility provides peace of mind with the assortment of today’s fertilizer blends. However, they are also more expensive than other chelating agents and are not needed in some of the simpler, more generic starter blends.

  • For example, poly-phosphate blends (10-34-0) do not require EDTA chelation. Citric chelates, such as our Source Zinc 10, are more affordable and provide a strong enough bond to be effective in some starters.

Author: Ethan Enochs

 
 
Ethan Enochs