What is Compost Tea?

I often joke with our students in the flagship Edible Learning Lab when we begin the process of making compost tea.  “Who wants a cup of tea?” is my usual lead in.  The veteran Labbers always play along daring the newbs to agree to a frothy cup.  But clearly, allowing students to actually drink such a concoction would require an iron clad release to be signed by the parents!

So what is compost tea?

Compost Tea Defined

Compost tea is a liquid extraction of nutrients and microorganisms from finished compost or worm castings used as a foliar spray or soil amendment. Compost tea can be made by leaching the nutrients and microorganisms with aeration.  Often, other supplements are added during the steeping process to aid in the proliferation of the beneficial microorganisms and bacteria.  We typically use molasses as a food source for feeding the bacteria.

The tea is “brewed” using an aeration pump, water, molasses, and a few cups of finished compost.  In short, the process extracts the nutrients and beneficial bacteria from the compost so that it can be diluted and sprayed on plants or used as a drench on the soil.  The end result is the introduction of a bloom of beneficial bacteria, organic particles, and bio-available nutrients that improve the soil immediately and in a number of ways.

How is Compost Tea Applied?

Compost tea can be applied directly to the soil or on plants as a foliar spray.  In either case, it is diluted before it is applied.

What are the Benefits of Compost Tea?

Used a soil drench, the diluted compost tea adds bacteria and fungi to the soil as well as a food source for the biota that already exists.  When used as a foliar spray, the compost tea is sprayed on the leaves allowing the microbes to colonize the leaves, deliver nutrients directly to the plant, and help to protect the plant from pests and diseases. The benefits include the following.

• Inoculate soil with beneficial microbes
• Improve plant health to better fight pests and diseases
• Soluble nutrient delivery
• Provide feed for soil organisms

You can refer to The Complete Guide to Vermicomposting that came with your Worm Factory 360 (pages 32-33) for more information on worm teas and leachates.