DTPA, diethylenetriaminepentaacetic acid, is a synthetic chelating agent with eight binding points, gripping metals more strongly than EDTA. Fe-DTPA, about 10-11% Fe, is the most common form in horticulture.
In practice
Fe-DTPA holds iron in solution up to roughly pH 7.0-7.5, giving a safety margin when root-zone pH drifts high in coco, rockwool or recirculating hydro. Many professional greenhouse recipes use it as the default iron source for that reason. It is also used in soil testing as an extractant for micronutrients, which is why "DTPA-extractable" appears on soil reports. Like EDTA, it degrades under strong light.
Don't confuse with
- EDTA: less stable above pH 6.5.
- EDDHA: stable to pH 9 or more.
- DTPA soil test: a lab extraction method, not a fertiliser recommendation.
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.EDTA (ethylenediaminetetraacetic acid) is the most common synthetic chelating agent in fertilisers, effective for iron up to about pH 6.0-6.5.An iron chelate is iron bound to an organic molecule (EDTA, DTPA or EDDHA) that keeps it dissolved and available; each type holds up to a different pH.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.A recirculating (closed) system returns drained nutrient solution to the reservoir to be reused, saving water and nutrients but needing more monitoring and sanitation.A micronutrient is an essential element plants need only in trace amounts, below a few mg/L: iron, manganese, zinc, copper, boron, molybdenum, chlorine and nickel.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.Iron (Fe) is an immobile micronutrient needed to make chlorophyll and run electron transport; deficiency yellows new leaves between green veins.
