In the course of preparing for our worm composting demo last week Kelly and I came across a lot of conflicting information. One of the most contentious issues in worm composting is what to do with the liquid that comes off the worm bin, called leachate.
The controversy stems, in large part, from the debate over aerated compost tea (ACT) vs. non-aerated compost tea. Fans of ACT do not like the fact that worm bin leachate is anaerobic, which they believe encourages the growth of microorganisms unfavorable to plants. They like to point out that worm bin leachate is not ACT.
The ACT debate needs a much longer post, but I did find two peer reviewed studies showing the benefits of un-aerated worm compost leachate: “Vermicomposting Leachate (Worm Tea) as Liquid Fertilizer for Maize“ and “Vermicompost Leachate Alleviates Deficiency of Phosphorus and Potassium in Tomato Seedlings.” I also found several Extension Service publications touting the use of worm bin leachate.
There are some caveats, however. First, it needs to be diluted–at least 1:1 and maybe, according to some sources, as much as 1:10. And you should probably test it out on a few plants before applying it to your whole garden.
And, from a food safety perspective, I’d avoid applying it to leafy greens and lettuces. I’d also point out that if you have a lot of leachate it might mean that your worm bin has too much moisture in it.
What do you think? Have you used worm bin leachate successfully? What side of the aerated vs. non-aerated debate are you on?