Compost tea is a liquid produced by leaching soluble nutrients and extracting bacteria, fungi, protozoa and nematodes from compost.
Compost tea is used for two reasons: To inoculate microbial life into the soil or onto the foliage of plants, and to add soluble nutrients to the foliage or to the soil to feed the organisms and the plants. Chemical-based pesticides, fumigants, herbicides and some synthetic fertilizers kill a range of the beneficial microorganisms that encourage plant growth. High quality compost tea is used to re-populate the leaf surface and soil with beneficial microorganisms.
Environmental conditions, although they vary, commonly include numerous negative impacts that kill the microbial populations on an ongoing basis. They include air pollution, prior pesticide and herbicide use, drift and overspray, synthetic fertilizers, water pollution, chlorine, current building and agricultural practices, over or under watering, compacted soils, unusual freeze, drought, flood, etc.
Repeated applications re-establish the beneficial microbes that suffer or can be killed under the above abuses.