Friday, July 18, 2008

Have a Tea Party with Your Veggies!

Here is an interesting way to use your compost in a foliar application: compost tea. Many gardeners swear by its affects in perking up their plants!

What is Compost Tea?

Compost tea is a small amount of compost steeped for a short time in water, much like brewing tea from tea bags. The result is a rich solution containing both beneficial organisms and nutrients that you use when watering or to spray on leaves.

What are the Benefits of Compost Tea?

I originally thought the benefit of compost tea was simply as an organic replacement for water-soluble fertilizers like Miracle Gro or Peter's Plant Food. It turns out that compost tea is actually much more than a mild fertilizer. It also helps inoculate your plants against disease by introducing beneficial bacteria and fungi to the soil or leaves. The process of making compost tea creates an environment where beneficial organisms flourish at the expense of harmful ones.

Bacteria and fungi are very important in the soil, helping roots absorb water and nutrients. These organisms are also important when present on leaves. Spraying plants with compost tea helps control various mildews, molds, blights, and wilt diseases. The theory is that the beneficial organisms compete with the bad ones for food and space. They may even actively kill harmful organisms by eating them or creating natural antibiotics.

How Do I Make Compost Tea?

Compost tea is relatively easy to make from finished compost. Simply fill a 5-gallon bucket about 3/4 full with room temperature, chlorine-free water (either let tap water sit out for a day, use rainwater, or dip some water from a pond or stream.) Then add one shovel-full of fresh compost and stir. You can also use cheesecloth or another loose fabric to hold the compost as you steep it.

Let the mixture sit overnight (stir it occasionally if you're around). When you return, strain the top half of the liquid through a screen or cloth and spray it on plant leaves or water with it. You must use the tea soon after brewing it; otherwise oxygen in the water will be depleted and the beneficial organisms will die or go dormant.

Oxygen-loving (or aerobic) bacteria and fungi are generally helpful. Anaerobic organisms (those that can live with no oxygen) are usually not beneficial, can cause disease, and just plain stink! If you can't use your tea within 12-18 hours after starting it, you will need to aerate it to add oxygen. You can do that with an electric sump pump to circulate the liquid, or better yet by pumping in air. You can use a regular aquarium air pump to oxygenate the tea.

If you aerate your tea, you'll get the best results if you use it within 1-3 days. If you need to keep your tea for longer than that, add a cup of un-sulfured molasses (or other sugar source) every few days to make sure there's enough food to satisfy your growing colony of beneficial organisms.

After using your compost tea, add the remaining solids back to your compost pile, or mix it into the soil.

Never use bad-smelling compost tea. That's a sure sign there are too many nasty anaerobic organisms lurking in it. If your tea smells like sewage, aerate it for a day or two until the smell goes away. (However, you can use your tea if it simply smells yeasty. Foam that may form on top of your tea is not bad for your plants either.)

More Reading

Here are some compost tea resources and recipes on the web.

Compost Tea Basics at GardenWeb

Compost Teas for Plant Disease Control at ATTRA

Brewing Compost Tea by Elaine Ingham

Compost Tea at PA EPA

Compost Tea by Doug Green

Copyright © 2003 Brian Ballard. All rights reserved.

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