This post is directly pulled from Organic Hobby Farming by Andy Tomolonis.  Thanks, Andy!

How do you make compost even better? by steeping it into microbe-rich compost tea – an organic elixir with the power to make plants stronger, healthier, and more resistant to disease.

But making compost tea isn’t as simple as soaking compost in water.  To encourage microbes, you need oxygen, so the water needs an air pump.

When properly made (with active compost and good aeration), compost tea produces billions of beneficial aerobic microbes that help plants resist pathogens.  How?  You can spray the billions of beneficial bacteria created in an aerobic solution onto leaves, where they will remain and feed off sugary solutions exuded by plants.  Once the good bacteria  are in place, they crowd out other, potentially harmful pathogens, preventing them from attacking your plants.  And, while compost isn’t usually a source of major nutrients, the micronutrients delivered in compost tea can help produce crops with higher nutritional value.  You can also mix compost with fish emulsion or another foliar feed.  Together the mixture can provide nutrients when plants are taking up enough material from their roots alone.

Pouring compost tea into soil at the base of plants adds bacteria, protozoa, and nematodes to the root zone.  In a healthy soil, the microbes continue to multiply and boost biological activity.  Their presence also helps protect plants from harmful fungi and bacteria.

Organic supply companies sell numerous kits for making compost tea, from small bucket-size brewers that sell for under $100 and make a few gallons at a time to commercial units that brew hundreds of gallons and cost thousands of dollars.  You can also make your own compost tea brewer using household supplies and a few items from a department store or aquarium supply shop.

What You’ll Need

  • 1 large air stone (a 6″ disk is ideal; a 6″ wand will suffice)
  • Two 5 gallon utility pails that haven’t been used to store detergents or harsh chemicals (food-grade buckets are ideal)
  • 1 heavy-duty aquarium air pump
  • 6′ long aquarium hose
  • 5 gallons of non-chlorinated water
  • 1 large mesh bag to use as strainer


  1. Place the air stone or stones at the bottom of one pail and attach it to the pump.  If your water contains chlorine, fill the bucket with water and run the pump for at least an hour, which should allow the chlorine to evaporate.  (Note: this is a vital step; chlorinated water will kill the microbes that you’re trying to cultivate.)

  2. When your water is ready, put the air stone or stones at the bottom of the second pail.  Fill the bucket half-full with compost but don’t pack it down.

  3. Add the non-chlorinated water from your other bucket until it’s about 3″ from the rim (you don’t want to spill it).

  4. The idea temperature for microbe growth is 70ºF, so if it’s cold outside, move your arrangement to a warm room indoors.  Plug in the pump and watch the bubbles.  The air should circulate around and through the compost.

  5. Once the bubbles are working, some brewers mix in food to hasten the growth of microbes, But there are cautions against adding molasses or sugars, which feed both good and bad bacteria.

  6. Allow the air pump to run for 12-24 hours, stirring frequently with a stick or dowel (allowing microbes to release from compost, circulate and multiply).

  7. After 12-24 hours, the bacteria will be read to use.  Shut off the pump and pull out the air stone.

  8. Pour the tea from one bucket into the other, using the mesh bag or mesh material as a filter.

  9. If you’re using the tea as a soil drench, pour it on your crops immediately.  If you want to use it as a foliar spray, strain it again to remove any compost particles, which can clog a spray nozzle.  The best flow will be achieved with a compost tea nozzle, which allows occasional particles to pass through.  You can also pour the tea into a watering can and sprinkle it over your plants’ foliage instead of spraying.

Additional tips:

Do not store tea for later use.

Apply in evening or early morning.

If it smalls sour or like rotten eggs, there may be anaerobic bacteria in it.  Discard.

Note: I highly recommend this book, since it does a great job outlining what a small farmer like myself might need.  Also includes a section on what tools to buy, which I am always a fan of.

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