Compost tea is a low-strength, natural fertilizer for seedlings and plants that can suppress fungal diseases like powdery mildew.
Methods for brewing it have been around for centuries. The first recorded note was by Pliny the Elder in ancient Rome. Way back, someone probably noticed how plants that were fed by rain running off a pile of rotting organic matter grew really well.
Benefits of Compost Tea
The tea-brewing process extracts nutrients and beneficial bacteria and fungi, suspending them in water, which makes them easy to absorb by the plants.
When you brew compost tea be sure to use mature, sweet smelling compost. If your compost smells bad it may be anaerobic (without oxygen). Few beneficial microbes can survive in that environment.
One way to achieve tea-worthy compost is to sustain pile temperatures of 135 to 155 degrees for a week or more, by turning the pile often. Or use compost from a well built pile that’s at least a year old, even if it did not heat up to the ideal temperature.
E. coli can be present in the raw ingredients of a compost pile, so minimize the risk by maintaining a hot pile or allowing enough time for the compost to mature fully. To be on the safe side don’t apply compost tea to any vegetable within 3 weeks of harvest.
How To Make Compost Tea
Making simple compost tea doesn’t require any special equipment. Here’s how to do it:
- Place about 10 pounds of compost (several shovels full) into about 10 gallons of water in a barrel (or 5 pounds in a 5 gallon bucket). Protect the barrel from cold or heat.
- Stir with a stick daily for a minimum of five days.
- Strain the liquid from the compost using cheesecloth or burlap. There should be no off odors. Use immediately without further dilution. You could add fish emulsion or powdered seaweed to the mix for more plant boosting power.
To make aerated compost tea is a more complicated process but will yield higher levels of valuable nutrients and microbes, making it more effective. This “high tech” but still DIY method was developed in the late 1990’s. It uses an electric motor to force air through the mixture, speeding up the process and adding more microbes. Most instructions call for an aquarium pump and tubing. The Pennsylvania Dept. of Environmental Protection has some illustrated instructions.
There is some debate among gardeners about whether compost tea is all that it’s cracked up to be. For further study check out Soil Foodweb’s page about aerated compost tea, which gives detailed, lab tested recipes for different plant needs.
Some of this information was drawn from Rodale’s Encyclopedia of Organic Gardening.