An iron chelate is ferric iron held in a ring-like organic molecule, the chelating agent, which stops it from forming insoluble hydroxides. The three common types are Fe-EDTA (about 13% Fe), Fe-DTPA (about 10-11% Fe) and Fe-EDDHA (about 6% Fe). They differ mainly in how high a pH they survive.
In practice
Fe-EDTA works well up to about pH 6.0-6.5, fine for most hydro but weak in high-pH soil or water. Fe-DTPA holds to about pH 7.0-7.5 and is the usual choice for coco and hydro. Fe-EDDHA stays effective to pH 9 or more and is used for alkaline soils; it stains solutions dark red. EDTA iron also breaks down in strong light, so opaque reservoirs help. Feeds typically target about 1-3 mg/L (ppm) Fe.
Don't confuse with
- Iron sulfate: unchelated iron, precipitates quickly above pH 6.
- Iron oxide or rust: insoluble and unavailable to roots.
- Amino acid chelates: weaker, less stable bonding, different behaviour in solution.
A chelate is a metal ion held by an organic molecule at several points, keeping micronutrients such as iron, zinc and manganese dissolved and available across a wider pH range.pH measures how acidic or alkaline a solution is on a 0–14 scale; in growing it controls nutrient uptake, with soil best near 6.0–7.0 and hydro 5.5–6.5.Coco coir is a growing medium made from processed coconut husk, prized for holding water and air at once; it binds calcium and magnesium unless buffered.EDTA (ethylenediaminetetraacetic acid) is the most common synthetic chelating agent in fertilisers, effective for iron up to about pH 6.0-6.5.Sulfate (SO4 2-) is the form in which plants take up sulfur, delivered mainly by magnesium sulfate and potassium sulfate in mineral feeds.An amino acid chelate is a metal bound to amino acids such as glycine; it is a gentler, biodegradable alternative to synthetic chelates, often sold for foliar sprays.Iron (Fe) is an immobile micronutrient needed to make chlorophyll and run electron transport; deficiency yellows new leaves between green veins.DTPA (diethylenetriaminepentaacetic acid) is a synthetic chelating agent that keeps iron available up to about pH 7.0-7.5, a common choice for coco and hydro.EDDHA is a strong iron chelate that stays effective up to pH 9 or more, used for alkaline soils and hard water; it colours solutions dark red.
