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Clive Edwards of Ohio State University gave a lecture here [Connecticut Agrigultural Research Station) today on vermicompost tea and its effects on a pretty amazing array of plant pathogens and insects (all in agricultural systems – cucumbers and tomatoes, mostly in the greenhouse, although he showed a few field experiments - no trees or lawns or landscapes). I just had a chance to talk with him, too. He was totally surprised that the vermicompost tea worked so well against so many agricultural pests (soil nematodes too – although he didn’t talk about that during his lecture), and he doesn’t really know what the mechanisms are yet.
Sharon Douglas videotaped the lecture, so we may have a DVD of the talk, but because he presented data that are not yet published, it will not be posted on the website or widely distributed, but just available on request from Sharon.
A few points from his talk:
Although he has experimented with different source materials, mostly his vermicompost was from food waste, using red wigglers
In his experiments with insects, he used different mixes of potting mix (Metro-Mix 360) and vermicompost, (100% potting mix, 90:10, 80:20, 60:40, 20: 80 – he says the plants don’t grow well in 100% vermicompost). In his field experiments with insects, he tried ranges of 5-10 tons of vermicompost per hectare (about 2-5 tons per acre). He says he has some evidence of effects at lower rates with the vermicompost applied in the row.
In his experiments with plant pathogens, there were a few with solid vermicompost, but mostly he used vermicompost tea
20% vermicompost tea (1 part vermicompost to 4 parts water brewing for 24 hours with aeration, but no other additions) was generally the most effective against the whole array of plant pathogens. He used soil drenches mostly in the greenhouse experiments, some foliar treatments in the field.
He does not add anything to vermicompost tea – he is especially against adding molasses or any form of sugar because of the danger of multiplying human pathogens.
We talked a good bit about vermicompost and tea and the National Organic Standards. He says that the NOP will allow vermicompost tea on edible food crops without the full waiting period on a “site specific basis” – including requirements for testing the tea for human pathogens. He suggests that people who want to make vermicompost tea from animal wastes do an initial hot composting for one week above the NOP required temperature, then cool everything down and finish the composting with worms.
His published papers are on his website – they are mostly peer-reviewed and you can download the pdf file for most, too (depending on the publisher)
Here is his more general website: