# Nitrogen

> Nitrogen (N) is the macronutrient plants use most, built into proteins, chlorophyll and nucleic acids; it drives leaf and stem growth and is fully mobile.

- Canonical: https://genetixbay.com/knowledge/glossary/nitrogen.html
- Also written: N, nitrogen deficiency, N deficiency, nitrogen toxicity
- 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"

Nitrogen is the element plants take up in the largest amount after carbon, hydrogen and oxygen. It is part of every amino acid, protein, [chlorophyll](https://genetixbay.com/knowledge/glossary/chlorophyll.md) molecule and strand of DNA. Plants absorb it mainly as [nitrate](https://genetixbay.com/knowledge/glossary/nitrate.md) (NO3-) and [ammonium](https://genetixbay.com/knowledge/glossary/ammonium.md) (NH4+), and they move it freely from old leaves to new growth.

## In practice

A deficient plant yellows from the bottom up, evenly across the leaf, while new growth stays green. Excess gives very dark, glossy leaves, clawed tips and soft, leafy growth. Hydro and coco feeds typically run about 150-200 mg/L (ppm) N in veg and somewhat less in late flower. Saloner and Bernstein found that lower N supply in flower can raise [cannabinoid](https://genetixbay.com/knowledge/glossary/cannabinoid.md) and [terpene](https://genetixbay.com/knowledge/glossary/terpene.md) percentage while reducing total yield, a trade-off rather than a free win.

## Don't confuse with

- **Nitrate**: one ionic form of nitrogen, not the element itself.
- **Iron or sulfur deficiency**: those yellow the new growth first; nitrogen yellows the old growth first.
- **Natural late-flower fade**: some lower-leaf yellowing near harvest is normal remobilisation.

## Myth check

The GenetixBay approach is to [taper nitrogen](https://genetixbay.com/knowledge/glossary/nitrogen-taper.md) in late flower, not to [flush](https://genetixbay.com/knowledge/glossary/flushing.md). Cut N back towards zero near the finish while keeping P, K, Ca, Mg, S and the micros fed. A plain-water flush starves the plant of everything at its most productive stage. See [the flush debate](https://genetixbay.com/knowledge/harvest-cure/flush-debate.md) and [Mythbusters](https://genetixbay.com/knowledge/mythbusters.md).

## Related terms

[Nitrate](https://genetixbay.com/knowledge/glossary/nitrate.md), [Ammonium](https://genetixbay.com/knowledge/glossary/ammonium.md), [Macronutrient](https://genetixbay.com/knowledge/glossary/macronutrient.md), [Mobile nutrient](https://genetixbay.com/knowledge/glossary/mobile-nutrient.md), [Urea](https://genetixbay.com/knowledge/glossary/urea.md), [N-P-K ratio](https://genetixbay.com/knowledge/glossary/npk-ratio.md)

## Read more

- [Nitrogen (N) in cannabis: nitrate vs ammonium, deficiency, toxicity and targets](https://genetixbay.com/knowledge/nutrients/nitrogen.md)
- [Yellowing lower leaves on cannabis: a differential](https://genetixbay.com/knowledge/diagnosis/yellowing-lower-leaves.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. Saloner A, Bernstein N. 2020. Response of medical cannabis (Cannabis sativa L.) to nitrogen supply under long photoperiod. Frontiers in Plant Science 11:572293. https://doi.org/10.3389/fpls.2020.572293
3. Saloner A, Bernstein N. 2021. Nitrogen supply affects cannabinoid and terpenoid profile in medical cannabis (Cannabis sativa L.). Industrial Crops and Products 167:113516. https://doi.org/10.1016/j.indcrop.2021.113516