Compost Tea and Extract
- Caitlin Youngquist
- Mar 27
- 3 min read
Updated: Apr 10
Compost tea is generally defined as a liquid extract of compost. It contains plant nutrients, beneficial microorganisms (bacteria, fungi, protozoa, nematodes) and the foods they eat, enzymes, organic acids, and natural plant growth promoting compounds that have been extracted from the compost.
With compost tea and extract, a little bit goes a long way. Compost can be expensive to transport and apply in large quantities but many of the beneficial components of compost can be extracted and applied over a larger area with relative ease and at a lower cost.
Healthier plants are more resistant to disease, and soil microbial diversity contributes to plant health.
If you are working with soil that is low in organic matter and biological activity, things like compost extract, fish hyrolysate, and microbial inoculants will help give the biology a boost and start building soil.
Compost Extract is produced without the brewing process that stimulates microbial growth. The microbes, water soluble nutrients, and organic compounds are quickly extracted (or leached) from the compost using water and agitation. Because the microbial activity is lower than compost tea, it has a longer shelf life and is easier to transport and use.
Compost Tea is produced using a variety of brewing methods that stimulate microbial growth with air and allows time for the microbes to multiply. It takes longer to make, has a higher microbial population than compost extract, and a very short shelf life.
Good quality compost tea and extract are very safe! Unlike fertilizers, they cannot burn or otherwise harm plants when used in high concentrations.
Our Compost Extract is now available state wide through Eat Wyoming.
How to use compost extract in the garden:
Use full strength or diluted as a soil drench when planting seeds, or as a root dip at transplanting.
Apply as a foliar feed and root drench when vegetable plants are 4 to 8 inches tall.
Apply again as a foliar and root drench at flowering.
Great for houseplants too!
Compost Extract can be used at full strength or diluted with filtered water or rain water if you want to stretch it. The chlorine in city water will reduce the activity of beneficial microbes.
Compost tea and extract provide many benefits for plants and soil:
Plant available nutrients improve plant growth, health, and yield. Compost extracts contain all essential plant nutrients.
Beneficial microorganisms increase nutrient cycling in the soil, stimulate plant growth, and help plants adapt to stress.They may also protect the plant from disease by occupying infection sites and preventing disease-causing organisms from getting established.
Organic compounds stimulate plant growth, help build soil, hold water and nutrients in the root zone, and improve soil structure.
Compost Extract is most effective when fresh but can be stored for a few months in a cool, dark location. Microbial activity will slowly decline over time.
Much like sourdough, the beneficial microorganisms in compost (and therefore compost extract) will vary based on location and ingredients. Diversity matters when it comes to the compost used to make extract. A diversity of feedstocks will help support a diverse range of microbes which will then support more diverse (and resilient) soil life.
There are many different ways to make compost tea (or extract) and for that reason it is challenging to define and research. The quality of compost tea or extract depends on the ingredients and the methods. Because the quality, and therefore the effects, of compost teas are highly variable, so are research results when it comes to impacts on specific plant diseases.
More information about compost teas and extracts, including how to make your own:
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