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Re: NOSB minutes on Compost Tea
Let's clarify the different kinds of compost tea that you might be concerned with, and ones that you don't need to be concerned with. If I forget a category, or you see the need to split a category, please chime in -
First, if you apply tea made from any source more than 90 to 120 days before the crop surface would be consumed, there are no worries.
Second, compost tea made from plant-based, no human waste compost. E. coli is not present in the starting materials, not present in the compost. This category should be of no concern to folks with respect to the human pathogen question.
Third, compost tea made with food waste material that could have low levels of E. coli. E. coli is fairly easily reduced to non-detectable levels with this type of compost. Testing might be necessary to document that E. coli is not present in the final compost material, and that it is then safe to apply to food plants.
Fourth, manure-based tea is what the E. coli concern is all about. We can make compost tea from manure-based compost without any E. coli in the final tea. BUT people also manage to make compost tea from manure-based compost that contains E. coli.
The problem becomes, how do you KNOW that you managed to exit the E. coli from the tea? What are the parameters that allow E.coli (and other human pathogens) to be destroyed? We have done it, but now we need to understand what the important factors are in producing these teas routinely.
So, that's where the situation is. Don't go ballistic about compost tea in general. But on plants that you eat without washing the surface of the material you are going to consume, stay away from compost tea made with manure-based compost.
President, Soil Foodweb Inc.