# DTPA

> 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.

- Canonical: https://genetixbay.com/knowledge/glossary/dtpa.html
- Also written: diethylenetriaminepentaacetic acid, DTPA chelate, pentetic acid
- Glossary category: Nutrients · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

DTPA, diethylenetriaminepentaacetic acid, is a synthetic [chelating agent](https://genetixbay.com/knowledge/glossary/chelate.md) with eight binding points, gripping metals more strongly than [EDTA](https://genetixbay.com/knowledge/glossary/edta.md). [Fe-DTPA](https://genetixbay.com/knowledge/glossary/iron-chelate.md), about 10-11% Fe, is the most common form in horticulture.

## In practice

Fe-DTPA holds iron in solution up to roughly [pH](https://genetixbay.com/knowledge/glossary/ph.md) 7.0-7.5, giving a safety margin when root-zone pH drifts high in [coco](https://genetixbay.com/knowledge/glossary/coco-coir.md), rockwool or [recirculating hydro](https://genetixbay.com/knowledge/glossary/recirculating-system.md). 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](https://genetixbay.com/knowledge/glossary/micronutrient.md), 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.

## Related terms

[Chelate](https://genetixbay.com/knowledge/glossary/chelate.md), [Iron chelate](https://genetixbay.com/knowledge/glossary/iron-chelate.md), [EDTA](https://genetixbay.com/knowledge/glossary/edta.md), [EDDHA](https://genetixbay.com/knowledge/glossary/eddha.md), [Iron](https://genetixbay.com/knowledge/glossary/iron.md)

## Read more

- [Iron (Fe) in cannabis: yellow new growth, chelates and pH](https://genetixbay.com/knowledge/nutrients/iron.md)
- [Hydroponic salts explained: what each fertiliser salt supplies](https://genetixbay.com/knowledge/nutrients/hydroponic-salts.md)

## Sources

1. HortScience. 2025. Iron chelates (Fe-EDTA, Fe-DTPA, Fe-EDDHA) in high-pH soilless media. HortScience 60(3):404. https://journals.ashs.org/view/journals/hortsci/60/3/article-p404.xml
2. Sonneveld C, Voogt W. 2009. Plant Nutrition of Greenhouse Crops. Springer. https://doi.org/10.1007/978-90-481-2532-6