Brewing compost tea and extracts

What’s the difference between an extract and a tea?

An extract takes a range of soil microbes from solid compost and suspends them in a water solution, in order to spread it on soil. It is a fairly instantenous process.
Extracts are typically applied directly to the root zone as soil drenches, for the organisms to start nutrient cycling there.

Compost tea, on the other hand, takes an extract and through a brewing process increases the numbers of microorganisms over a period of time, by aerating the water and feeding the microbes.
Microorganisms create secretions, which make them more likely to attach themselves to the surface of leaves or the soil. This is useful to protect the leaf surface from pathogens, for example rust or blight spores, or harmful bacteria. If a surface is well-covered with beneficial, aerobic organisms, pathogens have a much harder time.

Be mindful about the following specs, to avoid brewing pathogens:

  • All parts must be easy to reach and easy to clean.
    Where a biofilm settles, it can go unaerobic. Anaerobic environments foster plant pathogens, and also potentially human pathogens.
  • Avoid harsh 90degree bends through which microbes are propelled at speed. These can damage microbes on impact.
  • Consider durability and embodied energy.
    Are materials part of the the circular economy? Can the parts and brewer be repaired and maintained long-term?
  • If it is plastic, think about where you can store and use it to minimise plastic getting brittle through sun exposure.

Here are some European suppliers, so far, I haven’t tested their products, but I would consider a closer look at:

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