Vermicomposting worm castings, and plant health
Research shows worm compost has growth benefits that excede even those of plain compost

By Don Lotter, Ph.D., The Rodale Institute
Matt Ryan, research technician at The Institute, helped write this research brief

January 17, 2003: Over the past decade research has shown that worm compost, or vermicompost, has a growth-promoting effect on plants that goes beyond the benefits of plain compost. An article in the IPM Practitioner (May /June 2002) discussed vermicompost’s ability to increase crop yields dramatically. One study found a 200% growth increase in lettuce when plants were germinated and transplanted in a mix with vermicompost. One of the main classes of active plant growth promoting substances found in worm castings are humic acids. These were found to be associated with significantly greater plant heights, leaf area, shoot and root dry weights in tomato and cucumber seedlings and better growth of flowers and raspberries. Vermicompost and aerobic compost teas made from vermicompost have been shown to suppress certain plant diseases. In Petri dish tests vermicompost teas have been shown to inhibit common fungal pathogens of plants such as Fusarium, Botrytis, Pythium, Phytophtora, Rhizoctonia, and Sclerotinia. Dr. Elaine Ingham says that plant protection by high quality compost is mostly due to the microbial activity in compost.

Vermicompost has also opened up new markets for farmers. With the right equipment and know-how farmers can turn their farm manure or organic waste into a product that has more benefits and a higher market value than normal thermophilic compost. Vermicomposting operations can vary in size from municipal sized units housing more than 45 million worms, to farm scale units with 300,000 worms. There are several companies that sell large-scale vermicompost systems (see the Biocycle issue cited below). Most of these systems are flow through units that continually process organic matter added to the top, harvesting the finished product when it falls out of the bottom. Vermicompost can also be made in windrows by placing fresh waste on one side of the row while harvesting from the other side.

Vermicompost can also be made on a smaller scale at home, without spending thousands of dollars on equipment. Red wiggler worms (Eisenia foetida) are the most common vermicompost worm, not the large night crawlers often used as fishing bait. Red wigglers are great decomposers and don’t mind living amongst each other in tight quarters with lots of organic matter. For more information on vermicomposting you can start with the The Compost Resource website http://www.oldgrowth.org/compost/vermi.html. The Dec 2002 issue of Biocycle has an article that summarizes farm-scale vermicomposting.


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