# Urea

> Urea is a 46% nitrogen organic compound that soil enzymes convert to ammonium; it is cheap in field fertilisers but a poor choice for hydroponic cannabis.

- Canonical: https://genetixbay.com/knowledge/glossary/urea.html
- Also written: CO(NH2)2, carbamide, 46-0-0, urea nitrogen
- 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"

Urea is a small organic molecule, CO(NH2)2, containing 46% nitrogen. It is the world's most used nitrogen fertiliser. Plants can absorb some urea directly, but most is first converted to [ammonium](https://genetixbay.com/knowledge/glossary/ammonium.md) by urease, a nickel-dependent enzyme produced by microbes and plants.

## In practice

In soil, urea behaves like a slow ammonium source and acidifies over time; it can lose nitrogen as ammonia gas if left on the surface. In hydro and [soilless](https://genetixbay.com/knowledge/glossary/soilless.md) systems it is a poor fit: it is not counted by [EC](https://genetixbay.com/knowledge/glossary/ec.md) meters as an ion until converted, its conversion depends on microbial activity, and the ammonium it releases can upset the NH4/[NO3](https://genetixbay.com/knowledge/glossary/nitrate.md) balance. Some liquid bottle nutrients and [foliar](https://genetixbay.com/knowledge/glossary/foliar-feeding.md) products include it. On labels, urea-N is often listed separately from nitrate-N and ammoniacal-N.

## Don't confuse with

- **Ammonium**: urea becomes ammonium; they are not the same compound.
- **Urine**: contains urea, but also salts and [sodium](https://genetixbay.com/knowledge/glossary/sodium.md); not a measured feed.
- **Uric acid**: a different nitrogen compound found in bird and bat manures.

## Related terms

[Nitrogen](https://genetixbay.com/knowledge/glossary/nitrogen.md), [Ammonium](https://genetixbay.com/knowledge/glossary/ammonium.md), [Nickel](https://genetixbay.com/knowledge/glossary/nickel.md), [Foliar feeding](https://genetixbay.com/knowledge/glossary/foliar-feeding.md)

## Read more

- [Nitrogen (N) in cannabis: nitrate vs ammonium, deficiency, toxicity and targets](https://genetixbay.com/knowledge/nutrients/nitrogen.md)
- [Nickel (Ni) in cannabis: essential, needed in traces, almost never worth adding](https://genetixbay.com/knowledge/nutrients/nickel.md)

## Sources

1. Marschner P (ed.). 2012. Marschner's Mineral Nutrition of Higher Plants, 3rd ed. Academic Press. https://doi.org/10.1016/C2009-0-63043-9
2. Brown PH, Welch RM, Cary EE. 1987. Nickel: a micronutrient essential for higher plants. Plant Physiology 85(3):801-803. https://doi.org/10.1104/pp.85.3.801