Ministry of Agriculture and Lands
Compost Tea: A Growing Concern
What is Compost Tea?
The term “Compost Tea” specifically describes the watery solution obtained by soaking compost in water in the presence of nutrients such as molasses, kelp, and rock dust. The term “Compost Tea” is sometimes used to include the following products:
- Compost leachate - leachate from the compost pile
- Compost extract - soaking compost in water
- Manure tea - soaking manure in water
- Herbal tea - soaking fresh green plant material in water
- Liquid manure - fermented plant and marine animal material
Compost teas are used as a foliar spray to suppress plant disease and/or a liquid fertilizer.
Compost Teas and Food Safety
Compost teas that are improperly prepared may contain pathogens, such as Salmonella and E. coli 0157:H7. Growers using compost tea must be certain that the compost tea does not contaminate food plants with organisms that may cause human illness. To this end, growers should discuss their use of compost tea products with knowledgeable professionals*, and should test the compost tea products to make sure that they are pathogen free.
For more information contact:
- National Organic Program Regulations Section 205.203 (USDA)
- National Organics Standard Board: Compost Tea Taskforce Report (PDF)
- Appropriate Technology Transfer for Rural Areas
- Bad Bug Book
- Compost Council of Canada
* The Compost Council of Canada may be able to direct you to a knowledgeable professional in your area.
