Compost Tea


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First, what is compost tea, and why is everyone raving about it?

Compost tea is the controlled extraction of microorganisms and nutrients from a small amount of high-quality compost (and additional nutrient sources) into water.

The water is aerated to vastly increase the extraction of microbes and to provide an environment that will breed many more microbes, favoring mostly those that thrive in an aerobic environment.

The tea is then sprayed on the soil and plants in order to inoculate the landscape with these beneficial aerobic microorganisms. It’s not a fertilizer but provides many of the same benefits and more.

Compost tea is especially important when there isn’t enough good quality compost around for your lawn and organic garden. Also, compost cannot be applied to plant leaves, but compost tea can. The benefits are immense.

“I gave my starving zucchini some compost tea before I went to bed last night. I woke up to find them perky and very happy looking. Amazing!”


A basic compost tea brewer, the Mini-Microbulator is a low-cost yet effective machine.

Designed by Tim Wilson at Microbe Organics and made under license by Keep It Simple (KIS), it produces good quality tea.

Instead of bubbling air through the water from the bottom of the pail, its unique design circulates and cascades the aerated liquid, much like a small fountain.

The whole assembly is extremely easy to set up, take apart, and clean.

The powerful pump will last for many seasons of home garden use.

Brew Kits

The above compost tea maker comes with one brew kit (with compost in a mesh bag) to get you started. Additional kits, with or without bags, are available.

The high-quality compost (about half-and-half worm compost and garden compost) in this kit is produced locally in Victoria.

Each KIS brew kit contains approximately two large cups of compost and one little plastic bag containing humic acid powder and organic alfalfa meal, for a single 5-gal brew. For extra benefit, you can add 2 tbsp of molasses when starting the brew.

The Mini-Microbulator does not require the compost to be in a mesh bag, in fact it’s recommended to pour the loose compost directly into the water. Other tea brewer models may be optimized for bagged compost. I offer both options in the drop down menu above.

Tip: The mesh bag is useful for filtering the finished tea before pouring it into a sprayer. It can be washed and reused!

Compost Tea Application

This video on making compost tea comes from Phil’s Smiling Gardener Academy where he has an additional 10 videos on compost tea and 30 or so other videos on effective microorganisms, mycorrhizal fungi and other microbial inoculants.

Brewing compost tea is easy. The brewer comes with instructions. Compost tea can be applied from a watering can, sprayer, or irrigation system. It is applied as both a foliar and a soil drench. It is important to use water that has no chlorine.

Like most liquid products, it is best applied in the morning, while evening would be the second choice (this is particularly beneficial for living inoculants, since some of the microorganisms are not interested in basking in the hot sun, so it’s nice to give them some time to acclimate to their new surroundings and find a place where they are happy).

Compost tea works best when combined with liquid organic fertilizer products (click on the ‘Organic Fertilizers’ link at right to learn more). Preferably, it would be applied in smaller, regular doses, such as monthly or even weekly during periods of stress/disease. At a minimum, it should be done once in the spring and once in the fall.

When pouring the finished tea into the sprayer, be sure to put a clean cloth (such as nylon, silk, cotton) over your sprayer to filter out particulate that may cause clogging.

As a foliar, it is applied undiluted, generally at 5 gallons (US) per acre (1/2 Litre per 1000 sq ft) for every 6 feet of average plant height. So if you have an orchard of 18-foot tall trees, you would apply more like 15 gallons per acre.

It is important to spray both the top and underside of the leaves and obtain at least 70% coverage. A mist (not too fine) from a sprayer works best for this. The whole plant can be sprayed.

For a soil drench, as much as 20 gallons (US) per acre (2 Litres per 1000 sq ft) is often applied once or twice a year. This can be mixed with any amount of dechlorinated water as is necessary to provide adequate coverage.

In summary:

  • Foliar – undiluted – 1/2 Litre per 1000 sq ft on all leaf surfaces to at least 70% coverage, monthly if possible
  • Soil – diluted as necessary – 2 Litres per 1000 sq ft, in the spring and perhaps fall

Compost Videos

Here are some videos through a microscope of vermicompost I have used in the past in my compost tea brew kits.

They were made by Tim Wilson, who has longer, narrated videos on his website,

Products Price Quantity Add to Cart
5 Gallon Mini-Microbulator Brewer$248.00
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1 KIS Brew Kit with mesh bag$12.00
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1 KIS Brew Kit without mesh bag$10.00
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