# Field capacity

> Field capacity is the amount of water a medium holds after it has been saturated and allowed to drain freely; in pots it is called container capacity.

- Canonical: https://genetixbay.com/knowledge/glossary/field-capacity.html
- Also written: container capacity, pot capacity, water holding capacity, drained upper limit
- Glossary category: Systems and media · 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"

Field capacity is the [water content](https://genetixbay.com/knowledge/glossary/moisture-content.md) of a soil once gravity [drainage](https://genetixbay.com/knowledge/glossary/runoff.md) has stopped after saturation, usually a day or two after heavy rain in the field. In containers the equivalent is container capacity: the water a pot holds once it stops dripping after a full watering. Because a pot is shallow and has a perched water table at the bottom, container capacity is wetter than field capacity of the same material in the ground.

## In practice

Growers treat container capacity as "100% full". In crop steering, substrate water content is read with sensors or pot weight, and the first irrigations of the day bring the medium back up to near field or container capacity. The [dryback](https://genetixbay.com/knowledge/glossary/dryback.md) is then measured from that point. A pot that holds 6 kg of water at container capacity and is down to 4.8 kg has lost 20%.

Taller containers drain better and hold proportionally more air at container capacity.

## Don't confuse with

- **Saturation**: every pore full of water, before drainage; roots can't breathe for long.
- **Permanent wilting point**: the dry end of the range, where the plant can no longer extract water.

## Related terms

[Dryback](https://genetixbay.com/knowledge/glossary/dryback.md), [Wet-dry cycle](https://genetixbay.com/knowledge/glossary/wet-dry-cycle.md), [Air-filled porosity](https://genetixbay.com/knowledge/glossary/air-filled-porosity.md), [Crop steering](https://genetixbay.com/knowledge/glossary/crop-steering.md), [Overwatering](https://genetixbay.com/knowledge/glossary/overwatering.md)

## Read more

- [Drain-to-waste drip and crop steering (generative vs vegetative dryback)](https://genetixbay.com/knowledge/systems/drain-to-waste-crop-steering.md)

## Sources

1. Raviv M, Lieth JH, Bar-Tal A (eds), 2019. Soilless Culture: Theory and Practice, 2nd ed. Elsevier. https://doi.org/10.1016/C2015-0-01807-5
2. Brady NC, Weil RR, 2017. The Nature and Properties of Soils, 15th ed. Pearson.