# Monopotassium phosphate

> Monopotassium phosphate (MKP, KH2PO4) supplies about 22.7% phosphorus and 28.7% potassium with no nitrogen, and is the base of most PK boosters.

- Canonical: https://genetixbay.com/knowledge/glossary/monopotassium-phosphate.html
- Also written: MKP, KH2PO4, mono potassium phosphate, potassium dihydrogen phosphate, 0-52-34
- 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"

Monopotassium phosphate is the salt KH2PO4, sold as 0-52-34. That analysis is in oxides; the elemental content is about 22.7% P and 28.7% K. It is soluble, slightly acidic and free of nitrogen, [sodium](https://genetixbay.com/knowledge/glossary/sodium.md) and [chloride](https://genetixbay.com/knowledge/glossary/chloride-nutrient.md).

## In practice

MKP is the usual phosphorus source in mineral feeds and goes in the B stock, apart from concentrated calcium. Many "PK boosters" are mostly MKP. Because cannabis trials show a phosphorus plateau at moderate levels, a small dose is enough. Doubling it adds [runoff](https://genetixbay.com/knowledge/glossary/runoff.md), not buds.

## Units and formula

1 g/L gives about 227 mg/L (ppm) P and 287 mg/L K. Reaching 50 ppm P needs only about 0.22 g/L.

## Don't confuse with

- **Monoammonium phosphate (MAP)**: P with [ammonium nitrogen](https://genetixbay.com/knowledge/glossary/ammonium.md) instead of potassium.
- **Dipotassium phosphate**: K2HPO4, more alkaline and with a different ratio.
- **Phosphoric acid**: a liquid acid that supplies P while lowering [pH](https://genetixbay.com/knowledge/glossary/ph.md).

## Myth check

MKP is useful, but extra PK in flower does not raise yield past the plateau (Evidence: Established). See [bloom boosters](https://genetixbay.com/knowledge/nutrients/bloom-boosters.md).

## Related terms

[Phosphorus](https://genetixbay.com/knowledge/glossary/phosphorus.md), [Potassium](https://genetixbay.com/knowledge/glossary/potassium.md), [Phosphate](https://genetixbay.com/knowledge/glossary/phosphate.md), [Bloom booster](https://genetixbay.com/knowledge/glossary/bloom-booster.md), [Guaranteed analysis](https://genetixbay.com/knowledge/glossary/guaranteed-analysis.md)

## Read more

- [Hydroponic salts explained: what each fertiliser salt supplies](https://genetixbay.com/knowledge/nutrients/hydroponic-salts.md)
- ["Bloom boosters" for cannabis: what's real and what's marketing](https://genetixbay.com/knowledge/nutrients/bloom-boosters.md)

## Sources

1. Sonneveld C, Voogt W. 2009. Plant Nutrition of Greenhouse Crops. Springer. https://doi.org/10.1007/978-90-481-2532-6
2. Hershkowitz JA, Westmoreland FM, Bugbee B. 2025. Elevated root-zone P and nutrient concentration do not increase yield or cannabinoids in medical cannabis. Frontiers in Plant Science 16:1433985. https://doi.org/10.3389/fpls.2025.1433985