# Compost tea

> Compost tea is a liquid made by steeping compost or worm castings in water, often aerated with food sources, to extract and multiply microbes for the root zone.

- Canonical: https://genetixbay.com/knowledge/glossary/compost-tea.html
- Also written: aerated compost tea, ACT, AACT, actively aerated compost tea, worm tea, compost extract
- Glossary category: Systems and media · Evidence: Contested
- 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"

Compost tea is a brewed liquid in which compost or worm castings are steeped in water. Actively aerated compost tea (AACT) bubbles air through the brew for roughly 24-36 hours, often with a small amount of sugar source or kelp, to multiply aerobic microbes. It is applied as a soil drench or sometimes a [foliar spray](https://genetixbay.com/knowledge/glossary/foliar-feeding.md).

## In practice

Growers use teas to inoculate fresh soil with microbes, to support [living soil](https://genetixbay.com/knowledge/glossary/living-soil.md) between [top dressings](https://genetixbay.com/knowledge/glossary/top-dressing.md), and as a mild nutrient source. Use within hours of brewing, while the microbes are active. Brew in clean equipment; anaerobic, sour-smelling brews or teas made with molasses-heavy recipes can culture unwanted organisms, and there are food-safety concerns about foliar use on crops near harvest.

Evidence: research shows compost teas can suppress some plant diseases in some crops, but results are inconsistent and depend heavily on the compost and method. For cannabis yield, evidence is thin. Sugars in a brew feed microbes, not the plant.

## Don't confuse with

- **Compost leachate**: liquid drained from a compost heap; not a brewed tea.
- **Herbal teas (fermented plant extracts)**: different recipes and aims.

## Related terms

[Living soil](https://genetixbay.com/knowledge/glossary/living-soil.md), [Beneficial-microbe reservoir](https://genetixbay.com/knowledge/glossary/beneficial-microbe-reservoir.md), [Top dressing](https://genetixbay.com/knowledge/glossary/top-dressing.md), [Mycorrhizae](https://genetixbay.com/knowledge/glossary/mycorrhizae.md)

## Read more

- [Living soil (no-till, water-only organic growing)](https://genetixbay.com/knowledge/systems/living-soil.md)
- [Organic vs mineral nutrition for cannabis: what the trials show](https://genetixbay.com/knowledge/nutrients/organic-vs-mineral.md)