This is an excerpt from the book “The Earth Moved, On the Remarkable Achievements of Earthworms” by Amy Stewart. To set this up she has gone to meet with Clive Edwards, an oligochaetologist (scientist dedicated to the study of earthworms) who teaches at Ohio State University. In my next post I will have an addition to this to include amounts of worm castings needed to improve different size plots.
To set up the trials, he began with the standard soilless medium, typically a bark or peat mixture, that most growers use to start young seedlings. Then he started mixing in vermicompost (castings with some compost mixed in), at first adding only ten percent vermicompost to the mix and working up tp one hundred percent. He compared those plants to plants grown in the soilless medium only, and to those grown in the same medium with nitrogen, potassium, and phosphorous added to match those nutrients in the vermicompost.
“You don’t want to grow plants in vermicompost only,” he told me. “It’s like any other manure—it’s too much on its own. We found that adding twenty percent vermicompost to the soilless medium gets the best results…It may take four or five weeks to get a bedding plant like a petunia grown and out the door. We’ve been able to cut that time by one or two weeks, and the plant looks better.”
“One of my students did a very informal study,” he said. “He took some tomatoes and marigolds grown the ordinary way, and some grown in twenty percent vermicompost. He set up a booth outside one of our football games and asked people to assess their growth. The plants grown in vermicompost were much preferred over the others. They really did look better. That matters to a grower.”