General Gardening
Compost Teas
Compost teas have been used for centuries in European gardening. Plant and garden wastes contained in a permeable bag are immersed in water and left to create a tea thought to contain healthy microbes and nutrients. It's a passive, low-energy approach to creating extracts that can be used as a nonaerobic compost tea (NCT) foliar treatment of problems such as blackspot and powdery mildew or just added when watering.
The current, slightly more high-tech, approach is to use a brewer that aerates the water. This oxygenated tea is aerated compost tea (ACT) and is what is sold in nurseries and farmer's markets with the injunction that it must be used immediately for best results.
The problem is that compost teas may not necessarily work well or consistently. For $5 a gallon, you deserve some value for your money.
What's the problem?
The issue with compost teas is that there is no scientific research that supports the glowing claims offered by sellers. Most of the research has centered on the aerated compost teas with respect to different foliar treatments for powdery and downy mildews, black spot, and other offenders. The results have been underwhelming. Because scientific testing requires controls, the ability to replicate tests to collect statistically reliable data, and repeating the experiment several times to achieve supporting results, the value of compost tea is difficult to verify.
Each batch of tea is highly variable and that leads to inconclusive results. This inconsistency means that testing cannot provide a definitively positive or negative answer that it either really works or it doesn't.
To complicate the issue, ACTs may be enhanced with high-nutrient additives such as kelp or molasses to feed the microorganisms in the tea. Some research has documented the presence of human pathogens like E. coli and Salmonella in enhanced teas. As a result, disease control scientists are skittish about recommending a gardening practice that could result in serious illness, especially when used in vegetable gardens. Therefore, many advise caution in their use.
Just use compost
We've recommended it before and will probably grow endlessly repetitive on the subject, but just use compost! It's great stuff and serves a variety of purposes; compost:
- Helps soil retains moisture and maintains a more consistent, optimum soil temperature
- Prevents soil erosion and compaction
- Reduces weeds and as a consequence reduces the temptation to use pesticides
- Helps plants by improving soil nutrition which yields larger, stronger plants and that reduces disease
For more information
The Myth of Compost Tea—Examining the Science Behind the Claims by Linda Chalker-Scott, Ph. D. at Washington State University in Puyallup, WA.
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