Compost tea is an excellent fertilizer that helps increase the ecological diversity and vigor of soil. The tea provides nutrients directly to the plants because it is absorbed through their roots. It’s even been suggested that the flavor and nutrition of the food grown using tea is improved. The tea is also effective at preventing and treating disease.
The ideal compost to use comprises 25 percent high-nitrogen waste (fresh lawn clippings, alfalfa, peas), 45 percent green materials (kitchen scraps, old lawn clippings), and 30 percent woody matter (sawdust, newspaper, wood chips, old leaves).
Once you’ve got the right material in your compost pile, here’s what you need to start brewing:
- 2 5-gallon buckets
- 1 gallon of mature compost
- 1 aquarium pump and gang valve
- 4 gallons of chlorine-free water
- Aquarium hose, about 4 feet
- 2 aquarium bubblers
- 1 oz. unsulfured molasses (organic is best)
- 1 pillow case, pair of stockings, or cheesecloth—something you’re okay with throwing out afterward, as it’ll be used for straining
The key ingredient in this entire process is oxygen, and that’s where the aeration equipment such as the pump comes in. Without a constant supply of oxygen, the microorganisms will die and produce a bad odor. Anaerobic (without oxygen) tea also contains alcohol, which is harmful to plants.
How to Make Compost Tea
1. Attach one end of hose to the aquarium pump, and connect the other end to the gang valve.
2. Secure the gang valve to the side of the bucket, and attach a smaller section of hose to each port on the valve. The hose must be long enough to reach the bottom of the bucket. Attach the aeration bubblers to the end of the hoses.
3. Place the mature compost inside the bucket, making sure to cover up the ends of the hoses. Do not pack the compost; it must remain loose to help the aeration process.
4. Add water. If you are using water from a well or rain barrel you can simply add it to the bucket, but if it’s city water you need to get the chlorine out first, because it will kill the microorganisms. Evaporate the chlorine by pouring the water into the bucket before the compost and running the pump for about an hour.
5. Mix in the molasses. The sugar is a source of food and energy for the organisms living in the compost.
6. Turn on the pump and allow the mixture to brew for a maximum of three days. Stir it vigorously a few times per day, but make sure the hoses remain firmly attached to the valve and submerged. Brewing for longer than three days will exhaust the energy supplied by the molasses. (Add more molasses if you want to continue brewing.)
7. Use the pillowcase or old pair of stockings to strain the liquid into the second bucket. The leftover solids can be added to the soil or dumped back into your composting bin. This process should create about 2 gallons of compost tea. You can also place the compost inside the pillow case or stockings and hang it from the side of the bucket like a tea bag inside a mug—that way, when the tea is complete, you have less compost to strain out of the liquid.
8. Use the mixture within a day or two, because once the pump is off, the organisms inside the tea will consume the oxygen and begin to die. If it smells foul right away, don’t use it—something may have gone wrong during the process. It should smell sweet and earthy.
How to Use Your Tea
Compost tea can be applied to the soil surrounding plants (about a quart per plant) using a spray bottle or watering can. Spray the tea as soon as you plant to control disease and reapply every two weeks throughout the growing season, ideally before 10 am and after 3 pm, because the intense sunshine of noontime hours will kill the microorganisms. Rain will also wash away the tea, so spray on clear days.