One of the things we have to get straight here is our definitions of what we’re talking about when we talk compost tea. So here’s what happens when you don’t make compost tea but rather these other systems.
In simple terms, compost tea is an extract of compost where the bacteria, fungi, protozoa, and beneficial nematodes are increased in numbers using nutrients and oxygen provided by the gardener.
In short, oxygenated tea made from compost.
Compost tea is not…
Manure tea. This extract can contain soluble nutrients such as nitrogen, phosphorus, and potassium but it also contains high levels of bacteria. In many of these bacteria, such as E. coli, are not things that you want to put on your garden. Manure tea also often contains high numbers of root feeding nematodes.
Compost extract. This is produced by draining water through a compost pile. It contains soluble nutrients such as nitrogen, phosphorus, and potassium but very few beneficial microorganisms. Given that there are not high levels of these nutrients in compost, this is pretty much a waste of time but a relatively harmless practice.
Compost leachate. This is what is produced when compost is super-saturated and the water is collected. This leachate contains only the soluble nutrients and very very few beneficial microorganisms. One of the problems with compost leachate is that it is quite possibly anaerobic and not something we want to add to our garden. Different kinds of pathogens live in anaerobic (without oxygen) water/tea.