# Calcium nitrate

> Calcium nitrate is the standard hydroponic calcium source, supplying about 19% calcium and 15.5% nitrogen, mostly as nitrate.

- Canonical: https://genetixbay.com/knowledge/glossary/calcium-nitrate.html
- Also written: CaNO3, Ca(NO3)2, calcium nitrate tetrahydrate, cal nit, 15.5-0-0
- 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"

Calcium nitrate is a highly soluble salt that supplies both calcium and [nitrate nitrogen](https://genetixbay.com/knowledge/glossary/nitrate.md). The fertiliser grade most growers buy is a double salt with a little [ammonium](https://genetixbay.com/knowledge/glossary/ammonium.md), analysed at about 15.5% N (roughly 14.4% nitrate-N and 1.1% ammonium-N) and 19% Ca.

## In practice

It is the backbone of the A part in almost every two-part mineral feed. Because it reacts with [sulfate](https://genetixbay.com/knowledge/glossary/sulfate.md) and phosphate to form insoluble precipitates, it must never be mixed with [magnesium sulfate](https://genetixbay.com/knowledge/glossary/magnesium-sulfate.md), MKP or [potassium sulfate](https://genetixbay.com/knowledge/glossary/potassium-sulfate.md) in concentrated form. In the final dilute tank, they coexist without trouble. It is hygroscopic: keep the bag sealed or it turns to slush.

## Units and formula

1 g/L gives about 155 mg/L (ppm) N and 190 mg/L Ca. A feed of 0.8 g/L therefore adds roughly 150 ppm Ca and 125 ppm N.

## Don't confuse with

- **Calcium chloride**: supplies calcium without nitrogen but adds [chloride](https://genetixbay.com/knowledge/glossary/chloride-nutrient.md).
- **Calcium carbonate (lime)**: insoluble, used to raise soil [pH](https://genetixbay.com/knowledge/glossary/ph.md), not a hydro calcium source.
- **Cal-Mag**: a blended product, often based on calcium nitrate plus a magnesium salt.

## Related terms

[Calcium](https://genetixbay.com/knowledge/glossary/calcium.md), [Nitrate](https://genetixbay.com/knowledge/glossary/nitrate.md), [A/B nutrient](https://genetixbay.com/knowledge/glossary/a-b-nutrient.md), [Stock solution](https://genetixbay.com/knowledge/glossary/stock-solution.md), [Per-element dosing](https://genetixbay.com/knowledge/glossary/per-element-dosing.md)

## Read more

- [Hydroponic salts explained: what each fertiliser salt supplies](https://genetixbay.com/knowledge/nutrients/hydroponic-salts.md)
- [Calcium (Ca) in cannabis: deficiency, transport, targets and sources](https://genetixbay.com/knowledge/nutrients/calcium.md)

## Sources

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