Ferments vs Compost Teas

By Chris Gaffney

Ferments vs Compost Teas

What’s the Difference and When to Use Each 🌱

As growers start learning about microbes, soil health, and organic inputs, two terms come up a lot:

Ferments
Compost teas

They’re often talked about together — but they are not the same thing, and they serve different purposes in a grow.

To make sure this information stayed practical and accurate, I consulted with Isai, lead cultivator at ATX Organics, who works hands-on with both methods in real production environments.

Here’s a clear breakdown of what each one is, how they work, and when to use them.

 

What Is a Ferment? 🧪

A ferment is a nutrient extraction process.

The goal of a ferment is to:

  • Pull nutrients out of plant material

  • Preserve them in a concentrated liquid form

  • Make them easy for plants to access later

 

How Ferments Are Made (Simplified)

A basic ferment typically involves:

  • RO (reverse osmosis) water

  • A sugar source (usually molasses)

  • Plant material (whatever you want to extract from)

The process:

  1. Plant material is submerged in water

  2. Sugars provide energy for biological activity

  3. Naturally occurring microorganisms present on the plant material and in the sugar source begin the fermentation process

  4. Nutrients stored in the plant material are released into the liquid

No microbes are intentionally added during this process. Fermentation occurs because microorganisms already exist on plant surfaces and within organic inputs, and the sugar source fuels their activity.

After about two weeks, the mixture ferments in a warm, dark space, creating a highly concentrated extract of whatever nutrients were stored in that plant.

Think of ferments as:

A liquid nutrient concentrate made from plants

They are potent, so they are always diluted before use.

 

What Is a Compost Tea? ☕🌱

A compost tea is about microbial life, not extraction.

The goal of compost tea is to:

  • Multiply beneficial microbes

  • Feed those microbes

  • Deliver them alive to the soil or root zone

 

Two Common Compost Tea Methods

1. 24-Hour Brew

  • Often brewed in a 5-gallon bucket

  • Uses compost, microbes, molasses, and aeration

  • Brewed for about 24 hours

  • Applied immediately

This method works well for small home grows.

 

2. Constant Brew (Living Tea)

A constant brew system:

  • Uses a large vessel (often 55 gallons)

  • Is continuously aerated

  • Is regularly re-fed

Instead of starting over each time, the system is:

  • Heavily inoculated once

  • Then maintained by feeding:

    • Molasses (microbial food)

    • Liquid seaweed

    • Nitrogen or phosphorus sources (if desired)

Microbes are constantly:

  • Growing

  • Interacting

  • Competing

  • Becoming more resilient

This process is similar to re-amending soil — except you’re re-amending the tea itself.

Think of compost tea as:

A delivery system for living microbes

 

The Key Difference (In Plain Terms)

Ferments = Nutrient extraction
Compost teas = Microbial multiplication

Ferments:

  • Focus on what nutrients are present

  • Are concentrated

  • Are used in small amounts

Compost teas:

  • Focus on how alive the system is

  • Improve nutrient cycling

  • Support soil and root health

They serve different roles and are not interchangeable.

 

How These Fit Into Soil Growing 🌿

In soil-based systems, microbes already play a major role in nutrient availability.

Compost teas:

  • Increase microbial populations

  • Improve nutrient cycling

  • Support root zone health

Ferments:

  • Provide specific nutrients in plant-derived forms

  • Can supplement inputs naturally

Both methods align well with the principles discussed in growing in soil with biological inputs, where feeding the soil supports the plant.

 

When to Use Each

Use ferments when:

  • You want targeted nutrient supplementation

  • You’re extracting nutrients from specific plants

  • You need a concentrated input

Use compost teas when:

  • You want to improve soil life

  • You want better nutrient cycling

  • You’re focused on long-term soil health

Many growers use both — just not for the same purpose.

 

Final Takeaway ✨

🧪 Ferments extract nutrients
☕ Compost teas grow microbes
🌱 Both support soil health
🧠 They solve different problems

Understanding the difference helps growers apply the right tool at the right time — instead of treating them as interchangeable.

Big thanks to Isai of ATX Organics for sharing real-world insight that helped shape this breakdown.

Grown with care. Always. 🌿

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