Agriculture Reference
In-Depth Information
Making Compost Tea
To make a good tea, you need to get a lot of factors right — air pressure, water quantity,
size of the air bubbles, amount and types of compost and microbes foods, and on and on.
That means you either need to purchase a quality brewer that has been thoroughly tested
and has the data to support that, or build your own and test and tweak it until you get it
right. The first option may cost you at least a couple hundred dollars for a five-gallon brew-
er, but that's actually cheaper than the testing that needs to be done to properly build your
own. I use an excellent brewer made by Keep It Simple, and there are other great brewers
out there, too.
You can also buy a microscope and learn to test compost tea yourself — not cheap, but
lots of fun. You can learn more about how to brew good tea from Dr. Elaine Ingham's
Compost Tea Brewing Manual
. There's plenty of advice out there about how to build your
own brewer for as little as $25. This can be a lot of fun and you might make a decent tea,
but it generally works out that most homemade brewers don't make a good tea until they've
been tested and tweaked. There are just too many variables. You probably won't do any
harm, though, if you use good compost and if the resulting tea smells good, so it's a great
way to start experimenting. If you use a cheap aquarium pump, I recommend using only
one gallon of water in the bucket in order to ensure you have sufficient oxygen.
Whether you buy a brewer or make your own, here's how it works. You start with a
small amount of exceptionally good, aerobic, fully finished compost. A mixture of two or
three different composts is even better. Using different composts will bring more microbial
diversity, and you can even throw in a small amount of healthy soil. If you want to promote
a fungal tea, perhaps in order to establish an orchard or shrub garden or strawberries, use
compost that was made with a lot of woody material and still contains a small amount of
woody material. Even better, mix some oatmeal or oat bran into the compost a few days be-
fore you brew at three tablespoons per cup of compost. Keep this moist, dark and warm at
75F (25C) to promote fungal growth. For a bacterial tea, go for a less woody compost.
You can put this compost first into a mesh bag or directly into a bucket of clean, room
temperature water. By clean, I mean it can't have chlorine in it. If you use city water, you
need to let that bucket of water sit out for 24 hours for the chlorine to dissipate, or you can
turn your air pump on for 20 minutes instead and that also does the trick. If your city uses
chloramine to disinfect the water, you need to tie it up by adding ascorbic acid (vitamin C)
or humic acids. I use no more than half a tablespoon of my particular brand of humate in a
five-gallon brew.
Your pump will blow air through tubes that are in the bottom of the bucket, the tubes at-
tached with waterproof tape or weighed down somehow. The air goes through the water
and compost, keeping the environment aerobic to favor the aerobic microbes, and physic-
