Using Compost Tea in Your Garden
by Wade Collins

Compost tea can be a quick and inexpensive way to give your garden a helping hand during your growing season. Maintaining proper attention to ingredients and hygiene while “brewing” compost tea will ensure the maximum positive effect, while preventing potential bacterial contamination. Properly brewed tea can help you and your family to grow the healthiest gardens possible.

Well-brewed compost tea produces a microbe-rich solution with the dual purpose of increasing disease resistance and maximizing nutrient uptake. Compost teas confer a measure of disease resistance to a plant by allowing “good” bacteria to out-compete pathogenic organisms on a plant’s surface, while they can aid nutrient uptake in the root zone by increasing those populations of microorganisms known to provide this function for the plant.

There are two schools of thought regarding compost tea preparation. The first “school,” often referred to as the “European” method, is a decidedly low-tech affair. Here, mature compost is steeped in a loosely covered container of water for several days and stirred briefly by hand, once per day. The undiluted liquid is then applied to a plant’s leaves and  base to allow penetration of the root zone. The second “school” is a bit more technological in its approach. In the “American” method, mature compost is brewed in a container of water that is actively and forcefully aerated for a shorter duration (12 to 24 hours) and is often paired with an additional nutrient-rich additive capable of encouraging the rapid development of certain beneficial microbial populations.

Advocates of the American approach believe the constant aeration of the compost material increases aerobic activity while suppressing the development of pathogenic organisms. Recent studies, however, have shown that there is no inherent benefit to this method when it comes to protecting the tea against harmful bacterial contamination. On the contrary, it is the use of additives in the brewing process—especially molasses-based products—which creates the greatest opportunity for E. Coli, and other troublesome microbes, to flourish.

Whichever method you choose for your compost tea preparation, there are certain steps you can take to ensure that the resulting liquid is of the highest quality possible. In 2004, the National Organic Standards Board issued the Compost Tea Task Force Report; in it, they made various recommendations towards a best-practices approach to tea preparation. Included in those recommendations were the following:

• Use only high quality, potable water as a brewing medium.
• Sanitize all compost tea making equipment prior to each use.
• Use only mature, fully composted organic material in your preparations.
• Avoid the use of additives, or catalysts in your teas, but if you do use them, apply to food crops a full 90–120 days before harvest.
• Do not use compost tea for edible sprouts.

It’s also a good idea to brew your tea inside in a controlled environment. This makes contamination from outside sources, such as birds, animals and insects less likely.

For more information on compost tea, see eNewsletter Issue #57

For Information on Foliar Feeding, see eNewsletter Issue #20

A 10 gallon Compost Tea Maker and Tea Catalyst is available from the Garden Tools section of our website.

Wade Collins
Seeds of Change Research Farm Associate

Photo Cation: Field Manager Kelle Carter using a backpack sprayer to foliar feed kale plants