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The Spokesman-Review Newspaper
Spokane, Washington  Est. May 19, 1883

Compost tea seems worthy of a toast

Master Composter Ryan Herring recently gave a demonstration on making compost tea at Northwest Seed & Pet’s East Sprague store. (Susan Mulvihill)

Have you heard about compost tea? It’s all the rage these days but before I begin, I should clarify that you serve it to your plants rather than to the Queen of England when she pops by for afternoon tea.

Simply put, compost tea is made by steeping good-quality compost in a bucket of water to extract microorganisms to feed your soil. This technique has been used agriculturally for centuries; a more recent development is the addition of an aerator to provide a high-oxygen environment in which microorganisms will thrive and reproduce.

In addition to compost tea, there is compost extract. The former is applied to plant foliage to add nutrients and to improve its ability to resist foliar diseases such as powdery mildew. The latter is applied directly to the soil to increase its biological activity and diversity.

Master Composter Ryan Herring, who is also a WSU Spokane County Master Gardener, is convinced compost tea makes a huge difference in the garden. He recently demonstrated how to make it at Northwest Seed & Pet’s store on Sprague Avenue.

Making tea and extract requires the same general equipment, but the techniques vary.

“The difference between the two is what I put into the compost and the brewing time,” Herring said.

Supplies for a simple system include a clean 5-gallon bucket, 2 to 5 pounds of finished compost, a burlap or mesh “sock” to put the compost in (think of it as your tea bag), an aquarium pump, tubing, aerator stones and 4 gallons of non-chlorinated water.

Municipal water often contains chlorine which will kill microorganisms. To make chlorine dissipate, let the water sit in an open bucket for 24 hours before beginning the compost tea or extract process, or run the aerator in the bucket of water for one hour. Follow the same procedure for softened water; well water can be used right away.

To make extract, place the sock of compost into the bucket and knead the sock for one minute. Turn on the aerator and let it run for one to two hours. Herring then strains the bucket contents using a paint strainer to remove the solids that could clog a sprayer. Since microbes will die off quickly due to lack of oxygen and food, the strained liquid should be placed in a clean sprayer and applied to plants as quickly as possible.

Making compost tea involves more preparation and time. Three to five days prior to the aeration process, add 2 tablespoons of microbe “food” such as ground oatmeal, soybean meal, fish emulsion or worm castings to the compost. Then add 2 tablespoons of a microbe catalyst that is high in minerals, such as rock dust; garden centers and hydroponics businesses carry these. Mix well and place in a warm (about 80 degrees), dark area.

After three to five days, place the sock of compost into the bucket and aerate for 24 to 36 hours. Strain the bucket contents to remove the solids and spray immediately.

Herring is impressed with how well compost teas and extracts have worked in his garden.

“My vegetable plants are more productive and the vegetables are more flavorful,” he said. “And I haven’t seen powdery mildew on any of my plants.”

Susan Mulvihill is co-author, with Pat Munts, of “Northwest Gardener’s Handbook.” Contact her at inthegarden@live.com.