Compost tea is a liquid amendment made by steeping fresh compost in water. By using compost tea instead of chemical-based fertilizers, pesticides, and fungicides, you can garden in a way that is healthier for your plants and safer for the environment. Compost tea can help to:
- increase plant growth and extend root systems
- provide nutrients to plants and soil
- add beneficial organisms to the soil
- suppress plant diseases
Compost tea is completely safe and natural, as well as organic if made from organic compost.
The concept behind compost tea is very simple. Basically, compost (full of beneficial microorganisms) is put in water to allow the bacteria and fungi to multiply rapidly. Air is pumped through the water to keep it oxygenated, as this favors the beneficial bacteria and fungi over harmful ones. At the end of the brewing cycle, what you have is a concentrated liquid full of billions of microorganisms (bacteria, fungi, protozoa, nematodes) that can benefit your plants and soil in all kinds of ways.
Some gardeners make compost tea without aeration, but this is not recommended. Without pumping air through the mixture, the microorganisms quickly use up all the available oxygen and the tea becomes anaerobic, which favors harmful bacteria and could ultimately harm your plants.
Here is a simple and useful step-by-step how-to and brewing compost tea, reprinted from Fine Gardening http://www.finegardening.com/how-to/articles/brewing-compost-tea.aspx.
How to brew compost tea
To brew compost tea, you will need a 5-gallon plastic bucket and a few aquarium supplies: a pump large enough to run three bubblers (also called air stones), several feet of air tubing, a gang valve (which distributes the air coming from the pump to the tubes going to the bubblers), and three bubblers. You’ll also need a stick for stirring the mixture, some unsulfured molasses (preferably organic), and an old pillowcase, tea towel, or nylon stocking for straining the tea. An extra bucket comes in handy for decanting the tea.
Attach one end of a piece of tubing to the pump; the other end will connect to the gang valve. Attach tubing to each of the three ports on the gang valve. Plug bubblers into the other ends. Keep in mind that tea made using this bucket method needs to brew for two or three days and then be used immediately. If you work Monday through Friday, start the tea on Wednesday or Thursday, so it will be ready in time to apply it on the weekend.
If you’re on a well, you can use water straight from the spigot. But if you’re using city water, run the bubblers in it for about an hour first, to blow off any chlorine. Otherwise, the chlorine will kill all those beneficial organisms you’ve gone to the trouble of raising.
Once you have safe water, fill the empty bucket half full of compost. Don’t pack it in; the bubblers need loose compost to aerate properly. Cut a length of tubing and attach one end to the pump and the other to the gang valve. Cut three more lengths of tubing long enough to reach comfortably from the rim to the bottom of the bucket. Connect each one to a port on the gang valve and push a bubbler into the other end.
Hang the gang valve on the lip of the bucket and bury the bubblers at the bottom, under the compost. Fill the bucket to within 3 inches of the rim with water, and start the pump.
When it’s going, add 1 oz. of molasses, then stir vigorously with the stick. The molasses feeds the bacteria and gets the beneficial species growing really well. After stirring, you’ll need to rearrange the bubblers so they’re on the bottom and well spaced. Try to stir the tea at least a few times a day. A vigorous mixing with the stick shakes more organisms loose and into the tea. Every time you stir, be sure to reposition the bubblers.
After three days, turn off the pump and remove the equipment. If you leave the tea aerating longer than three days, you must add more molasses or the good organisms will start going to sleep because they don’t have enough food to stay active. Let the brew sit until the compost is pretty much settled out, 10 to 20 minutes, then strain it into the other bucket or directly into your sprayer. You’ll have about 2 1/2 gallons of tea. If you want, this is the time to add foliar micronutrients, like kelp or rock dust. Use the tea right away, within the hour if possible.
You can put the solids back on the compost pile or add them to the soil. There are plenty of good bacterial and fungal foods left in them.
Use the right kind of compost
To make good compost tea, you need actively managed, mature compost; that is, compost that has been turned a few times and allowed to heat adequately so weed seeds and pathogens have been killed. Worm compost also makes excellent tea, without the hassle of turning or checking the temperature. Tea brewed from vermicompost that has been made from a fair amount of paper and woody materials is also high in humic acid, an organic substance that is especially good for potted citrus or other trees and shrubs, or perennial plants.
Using the tea
How often to spray your plants with tea depends on how healthy your garden is. In my garden, which has had no pesticide use since 1986, I spray my plants one time in spring, then let the beneficial insects spread the compost tea organisms around the plants in my garden, preventing any pest problems for the rest of the season.
Beneficial insect presence is a good indicator of your garden’s health. If you don’t have good levels of beneficial insects in your garden, then spray at least once a month, or as often as once every two weeks. Start when plants have developed their first set of true leaves.
To control damping-off, spray the soil with full-strength tea as soon as you plant. On trees and shrubs, spray two weeks before bud break, then every 10 to 14 days. You’ll have to spray every 10 days if you have a neighbor who sprays pesticides, because pesticides kill the beneficial organisms as well as some of the pests.
Note: There are many other recipes for compost tea available on the internet. For those who would rather use a commercial machine, you can purchase them from several different companies. Here is an example: http://www.growingsolutions.com/home/gs2/page_295_81/compost_tea_system10.html?stpl=