# Potassium nitrate

> Potassium nitrate (KNO3) is a soluble fertiliser salt supplying about 13% nitrogen as nitrate and 38% potassium, used in both veg and flower feeds.

- Canonical: https://genetixbay.com/knowledge/glossary/potassium-nitrate.html
- Also written: KNO3, saltpetre, saltpeter, 13-0-46, nitrate of potash
- 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 nitrate is a salt of potassium and [nitrate](https://genetixbay.com/knowledge/glossary/nitrate.md), sold as fertiliser grade 13-0-46. That means 13% N and 46% K2O, which is about 38% elemental K. It is fully soluble and contains no [chloride](https://genetixbay.com/knowledge/glossary/chloride-nutrient.md) or [sodium](https://genetixbay.com/knowledge/glossary/sodium.md).

## In practice

It is the main way to add potassium while also adding nitrogen. It is compatible with [calcium nitrate](https://genetixbay.com/knowledge/glossary/calcium-nitrate.md), so it can sit in either the A or the B stock. Shifting part of the potassium from potassium nitrate to [potassium sulfate](https://genetixbay.com/knowledge/glossary/potassium-sulfate.md) or [MKP](https://genetixbay.com/knowledge/glossary/monopotassium-phosphate.md) lowers nitrogen while keeping K steady, which is one way per-element feeds taper N in late flower. Store it away from heat and combustibles, as it is an oxidiser.

## Units and formula

1 g/L gives about 130 mg/L (ppm) N and 380 mg/L K.

## Don't confuse with

- **Potassium sulfate**: supplies K and S, no nitrogen.
- **Sodium nitrate (Chile saltpetre)**: brings sodium, not wanted in cannabis feeds.
- **Potassium chloride (muriate of potash)**: brings chloride; avoided in hydro.

## Related terms

[Potassium](https://genetixbay.com/knowledge/glossary/potassium.md), [Nitrate](https://genetixbay.com/knowledge/glossary/nitrate.md), [Calcium nitrate](https://genetixbay.com/knowledge/glossary/calcium-nitrate.md), [Guaranteed analysis](https://genetixbay.com/knowledge/glossary/guaranteed-analysis.md), [Stock solution](https://genetixbay.com/knowledge/glossary/stock-solution.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