Agriculture Reference
In-Depth Information
Chapter 13
Compost Tea
There's a lot of excitement right now about the benefits of compost tea, and nearly as
much confusion about what it is. The benefits are all the same as those things microbes do
in the garden that were listed in the soil food web chapter, with insect and disease control
and plant health being the main reasons people use it. The confusion happens because of
the name. Gardeners have been making a form of compost tea for centuries by putting a
small amount of compost in a pail of water, sometimes inside a burlap sack, stirring it once
in a while for a few days, and then applying that water to the soil.
To me, that sounds like tea because it's a lot like making a cup of tea — put the tea bag
in the cup, add water, stir and drink. That's tea. Nowadays, this method might be called
non-aerated compost tea, or simply the bucket method, which is also confusing because we
use a bucket for the new method, too. This older method can extract some nutrients and
aerobic microbes from the compost if it remains aerobic, but the microbes generally won't
be very active and won't stick to the leaf surfaces when applied.
Even worse, some funky teas can result from the old method that may harm plants. You
can add foods to the tea to wake up the microbes, but in doing this then they use up more
oxygen and the tea can quickly go anaerobic. Immature compost may also make an anaer-
obic tea. Anaerobic tea may have its special uses, but it will be mainly composed of anaer-
obic bacteria and yeasts, not particularly diverse, and lacking aerobic microbes like fungi,
protists, and many bacteria. We want aerobic tea to restore more of the beneficial microbes.
So non-aerated compost tea can be helpful or harmful, and it's generally not optimal.
There's also traditional manure tea, which isn't aerated. The potential to extract harmful
microbes that exist in animal manure is greater, along with antibiotics, hormones and other
things we feed animals that aren't organically raised. Then there's compost leachate, which
is basically just the water that comes out of a compost pile that is too wet. Some people call
that compost tea, but it's very often an anaerobic, potentially toxic stew.
There's a newer game in town that involves bubbling air through the water with some
kind of air pump and adding specific foods to feed and multiply the microbes, and that is
now called compost tea. It's more accurately called aerated compost tea or even actively
