# Potassium sulfate

> Potassium sulfate (K2SO4) supplies roughly 41-45% potassium and 17-18% sulfur with no nitrogen, useful for adding K while tapering N in late flower.

- Canonical: https://genetixbay.com/knowledge/glossary/potassium-sulfate.html
- Also written: K2SO4, sulfate of potash, SOP, potassium sulphate, 0-0-50
- 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"

Potassium sulfate is the salt of potassium and [sulfate](https://genetixbay.com/knowledge/glossary/sulfate.md). Pure K2SO4 is about 44.9% K and 18.4% S; fertiliser grades are commonly sold as 0-0-50 or 0-0-52 (K2O), roughly 41-43% K. Solubility is lower than most hydro salts, around 110 g/L at room temperature, so concentrated stocks are limited.

## In practice

It is the go-to salt for raising potassium without raising nitrogen. In [per-element feeding](https://genetixbay.com/knowledge/glossary/per-element-dosing.md), swapping some [potassium nitrate](https://genetixbay.com/knowledge/glossary/potassium-nitrate.md) for potassium sulfate is how growers taper N in late flower while holding K steady. It belongs in the B stock, away from concentrated calcium, because calcium sulfate precipitates. Use soluble or "greenhouse" grade; agricultural granules can contain insoluble residue.

## Units and formula

1 g/L of pure salt gives about 449 mg/L (ppm) K and 184 mg/L S.

## Don't confuse with

- **Potassium chloride (muriate of potash, MOP)**: cheaper but adds [chloride](https://genetixbay.com/knowledge/glossary/chloride-nutrient.md).
- **Potassium nitrate**: supplies nitrogen with the potassium.
- **Potassium magnesium sulfate (langbeinite)**: a mixed mineral with Mg too.

## Related terms

[Potassium](https://genetixbay.com/knowledge/glossary/potassium.md), [Sulfate](https://genetixbay.com/knowledge/glossary/sulfate.md), [Potassium nitrate](https://genetixbay.com/knowledge/glossary/potassium-nitrate.md), [Per-element dosing](https://genetixbay.com/knowledge/glossary/per-element-dosing.md), [Sulfur](https://genetixbay.com/knowledge/glossary/sulfur.md)

## Read more

- [Hydroponic salts explained: what each fertiliser salt supplies](https://genetixbay.com/knowledge/nutrients/hydroponic-salts.md)
- [Potassium (K) in cannabis: role, deficiency, excess and K-Ca-Mg balance](https://genetixbay.com/knowledge/nutrients/potassium.md)

## Sources

1. Sonneveld C, Voogt W. 2009. Plant Nutrition of Greenhouse Crops. Springer. https://doi.org/10.1007/978-90-481-2532-6