Compost Tea: Brewing Billions of Microbes for Soil Restoration
How to brew Actively Aerated Compost Tea (AACT) — the microbial multiplication technique that turns 2 kg of compost into 200L of biological inoculant.
Compost Tea
Compost tea is water that has been "brewed" with finished compost and aeration to multiply beneficial microorganisms 1,000x. It is one of the most powerful tools for rapid soil restoration and transplant establishment.
Two Types
Actively Aerated Compost Tea (AACT): Bubbled with an air pump for 24–36 hours. Multiplies aerobic bacteria and fungi dramatically. The preferred method.
Non-Aerated Extract: Simple water extraction — simpler equipment, less microbially active. Still useful but AACT is significantly more potent.
AACT Recipe (200L Batch)
| Ingredient | Quantity |
|---|---|
| Water (non-chlorinated) | 200 L |
| Finished, mature compost | 2–4 kg |
| Molasses or jaggery | 200–400 g (microbial food) |
| Fish hydrolysate / FAA | 100–200 mL (optional — fungal food) |
Equipment: Aquarium-type air pump (minimum 1 CFM per 20L of water) with diffuser stones. A pump for a 200L batch needs to deliver ~10 CFM.
Brewing Process
- Fill container with non-chlorinated water
- Place compost in mesh bag (or loose — filter later)
- Add molasses/jaggery and fish hydrolysate
- Start air pump — maintain vigorous bubbling for 24–36 hours
- At 24 hours: tea should smell earthy and sweet, not foul
- Strain out compost material
- Apply IMMEDIATELY — within 4 hours of completing brew
⚠️ Compost tea bacteria die within 4 hours without food once removed from aeration. There is no shelf life. Brew and apply same day.
What 24–36 Hours of Aeration Does
Starting population (2 kg compost): ~200 million bacteria/mL
After 24-hour AACT brew: 200 billion bacteria/mL (1,000x multiplication)
The molasses provides the carbon energy. Aeration keeps oxygen levels high for aerobic bacteria. The result is an extraordinary microbial population ready to inoculate soil.
Application
| Method | Rate | Best Use |
|---|---|---|
| Soil drench | 200L per acre | Soil restoration, after chemical damage |
| Transplant drench | Dip root ball before transplanting | Ensures fast establishment |
| Foliar spray | Spray until runoff | Disease suppression (foliar bacteria) |
| Through drip | 200L diluted per acre | Convenient for large fields (50-micron filter) |
Best time to apply: Early morning, before sun heats soil surface.
When to Use Compost Tea
- Transplanting: Drench transplant holes before and after planting. Most effective single use.
- After chemical damage (if field received pesticide): Fastest biology restoration.
- Seed germination: Soil drench at seeding for fast establishment.
- Before cover crop incorporation: Boosts decomposition speed.
- Disease outbreak recovery: Flood the field with AACT — competitive exclusion.
Cost
| Item | Cost |
|---|---|
| Compost (2–4 kg) | ₹20–60 (own compost) |
| Jaggery (300g) | ₹12–18 |
| Air pump | ₹300–800 (one-time purchase) |
| Per brew (excluding pump) | ₹30–80 |