Ask a Master Gardener: ‘Compost tea’ probably not worth the effort
Household waste can be used to easily make compost, which probably is more effective than brewing "compost tea."Q: I'd like to try using compost tea in my garden this spring. What is the best way to make it?
A: The best way is probably not to make it at all.
Compost tea is a liquid brewed from compost and water. A lot of claims are made about its benefits, and you can buy all sorts of products to help you make it. Compost tea has passionate defenders, and there are even Extension sites that suggest giving it a try. But many experts caution there is limited scientific research to support its use.
You can see this controversy illustrated on the Oregon State University Extension site, which provides a diagram for making a compost tea brewer, but includes a note: "The making and use of compost tea has not been scientifically validated by Oregon State University."
The idea behind compost tea is that it contains nutrients, fungi and microbes that are good for your garden soil. And it does, but it's probably not better than just spreading compost on your soil. Compost has benefits that compost tea doesn't. It contains organic material that's good for your soil structure, and it contains food for the good microscopic critters in the soil.
In their book "Decoding Gardening Advice," horticulture professor Jeff Gillman and master gardener Meleah Maynard argue that using compost tea is an ineffective way to build up soil microbes.
"Applying compost tea to a poor soil is a lot like dumping a whole bunch of people in the middle of the Sahara Desert without any supplies," they write. "They are not going to build a new civilization; they are going to die."
Some people also believe that spraying compost tea on the leaves of plants will fight diseases, but research on foliar spraying has had mixed results.
It probably won't actually hurt anything if you use compost tea, but compost tea may contain harmful bacteria, such as E. coli or Salmonella.
Spreading compost on top of your soil is safer, probably more effective, and certainly a lot simpler than brewing compost tea.
Written by U of M Extension Master Gardeners in St. Louis County. Send your questions to features@duluthnews.com.