Methods and Resources for Brewing Compost Tea

Welcome back!

Last time we talked about the soil food web and the relationship between microbes and plants, so now let’s focus on how to brew compost tea.

Making Compost Tea
Photo Courtesy of The Tassie Farmer Blog

When brewing compost tea for microbes it’s best to avoid serving them a plate of toxins! Synthetic fertilizers kill off microbial life in soil, making it so you depend more heavily on those fertilizers. It becomes a vicious cycle and almost impossible to wean away from the bottles. Incorporating synthetic fertilizers would be counter-productive when brewing organic teas. If you plan on going organic it’s best to commit 100%.

Actively aerated compost teas (AACTs) foster the development of aerobic microbes by pumping air into a de-chlorinated water mixture of compost and microbial nutrients. Old-fashioned teas, which encourage anaerobic microbes, could possibly introduce pathogens into your garden, thus AACTs are the safest approach to take when considering brewing teas to feed your soil or soilless mediums.

One of the most important nutrients is Nitrogen; it is the basic building block of both amino and nucleic acids and is essential to plant growth and development. Some plants prefer their nitrogen as nitrates (NO3-), while others prefer ammonium (NH4+).

Nitrogen fixing bacteria convert NH4+ into NO3- and thrive in basic pHs above 7. Bacteria in compost will buffer pH to 7-7.5. Fungi will buffer pH to around 5.57, so you definitely want fungi present to prevent your tea from getting too alkaline. Fungi produce acids (organically) that decay organic matter for food. If enough fungal acids are present, then bacterial slimes could be offset and pH levels would drops below 7, making it turn acidic. It’s a very delicate balance!

Seasonal crops such as veggies and cannabis prefer Nitrogen in the nitrate (NO3-) form. With this in mind you are going to want a biomass in your compost tea that has a slightly higher ratio of bacteria to fungi.

So, how do you brew compost tea? There is no stringently written guideline to making compost tea, but there is a general template that you can tweak to suit your garden. Remember, always listen to your ladies and over time you’ll start figuring out which ingredients she’s yearning for.

Besides the necessary key microbes found in compost (or vermicastings, a good substitute) you’ll need de-chlorinated water, an air pump, and nutrients for microbes (which can be subjective) to brew actively aerated compost teas. Brewing tea should be performed under room temperature. Colder temperatures slow microbial activity and hotter temps either fries them up or makes them dormant. You also want to stay away from deadly UV rays. As Lowenfels & Wayne Lewis describes it in Teaming with Microbes, you should attain “rich, crumbly, dark, coffee-colored, sweet-smelling humus-soil that also happens to be full of life”. I used to think that making compost teas was restricted to bigger crops with more available work-space, but I found that a simple Home Depot 5gal bucket is more than enough.

Brewing in a 5-Gallon Bucket
Photo Courtesy of The Bay Branch Blog

There are lots of nutrient resources that you can choose from. At the end of this article there will be a few links to recipes to help you get started.

Here are some general ingredients that are yummy treats for microbes:

  • molasses (nonsulfured): food and energy source for microbial life
  • mixing the compost with proteins such as soybean, powdered malt, oatmeal, oat bran, or powdered baby oatmeal several days before brewing tea gives fungi a head start (good for Bloom teas) since bacteria multiply a lot faster than fungi take to grow– 3-4 tablespoons/cup of compost
  • Fish emulsion: good bacterial food and will also support fungal growth
  • Kelp, humic and fulvic acids, phosphate rock dusts, pulps of fruits, aloe vera extract and fish hydrolysate encourage fungal growth

Instead of straining your teas, use a porous bag (microbes can’t pass through anything smaller than 400 micron) to hold your compost and make cleaning easier. Foaming could be a sign of proteins being released from the compost and means things are working. It takes 24-36hrs to develop a good tea, and remember it should always have a sweet and earthy smell. Otherwise it’s probably gone anaerobic and should be discarded. The shelf life for compost teas is short and should be used within 4 hrs of making it. Putting tea in the fridge is a good idea because it can save for 3-5 days longer.

NOTE: Remember our foliar feeding post? Well, foliar feeding teas can act as a great natural defense against pathogens since the beneficial microbes dominate pathogens for both food and space. It usually takes 15-30 min for bacteria or fungi to attach to a leaf. And please be gentle, the velocity of sprayer should be slow and not exceed pressures of 70lb. Your medical marijuana garden will thank you!

There can be an impressive network of life in your soil if you properly foster it, but there could be an even more wondrous relationship between your medical marijuana plants and the world inside their soil if you empower it! More importantly, this community recycles and converts nutrients into readily accessible ones for your plants in a beautiful symbiotic relationship that growers should encourage.

Compost Tea Close-up
Photo Courtesy The Bay Branch Blog

While this article is meant to serve as an introduction to the microbe ARMY and the symbiotic relationship between them and your plants, there are several resources on the web that can also help guide you through the process of brewing compost teas. Soil scientist Elaine Ingham can help walk you through more detailed steps on how to brew teas in her awesome YouTube channel here.

Another great resource is @plant_n_prosper on Instagram. Next week we’ll be interviewing @plant_n_prosper, but here’s a sneak peak at his approach to the process of brewing teas:

“First, we need a brewer.  A solid 20 watt pump will suffice up to 15 gallons normally. I don’t recommend using air stones, as these are near impossible to fully sterilize after using… and you want a sterile brewer each and every time!

Typically it takes between 12-36 hours to complete a brewing process (but never over 48 hrs.), depending on temperatures of the tea itself.  I like to brew mine in my grow room to keep it right around 75° F

  • begin by bubbling off any chlorine/toxins in the water for an hour
  • add your foods and then your compost–I prefer to let everything float around freely rather than using a tea bag only because it agitates microbes easier than a tea bag does
  • before applying this tea to your garden you should strain the brew through a 400+ micron strainer (remember, microbes can’t pass through anything smaller than 400 micron)”

Again, your choice of food is subjective to your personal preferences and the needs of your particular medicinal garden.

If you’re looking for a great food resource for your girls then check out our friends, Dragonfly Earth Medicine. These guys have been brewing organic compost teas for a long time and know their microbiology! DEM is not only provides a complete superfood for your plants and microbes with no filters, but they’re also an awesome group of dedicated people who have your garden’s best interest at heart. You can learn more about DEM and their products by visiting their website here.

Dragonfly Earth Medicine

Because I started with a quote I feel it’s appropriate to end with one. Thanks for reading and I hope this information and additional resources helps you in your quest of brewing compost teas!

 “We cannot fathom the marvelous complexity of an organic being…each living creature must be looked at as a microcosm–a little universe, formed of a host of self-propagating organisms, inconceivably minute and as numerous as the stars in heaven.”

― Charles Darwin




4 thoughts on “Methods and Resources for Brewing Compost Tea

  1. Is it possible to apply compost tea via drip tube? The drip tube strainer is a 100 micron (155 mesh) screen. You say that no microbes will pass through anything smaller than 400 microns.

    I guess I just answered my own question? Can you comment on this?
    Applying compost tea via drip line would be too easy.

    1. Hi,
      Yes you can apply the tea directly to your growing medium or use as a foliar feeder. Thanks for checking out the Bounty Blog

Comments are closed.