Worm Castings Definition

Worm castings provide a valuable soil amendment.

People new to the hobby of worm farming may confuse the terms "worm castings" and "vermicompost," using both terms to refer to the manure created by the compost worm, Eisenia fetida, popularly known as the red wiggler. Vermicompost may take several months to be converted to pure worm castings, writes Mary Appelhof in "Worms Eat My Garbage." Both provide a nutrient-rich amendment to garden soil.

Identification

Ontario worm hobbyist Bentley Christie of the Red Worm Composting website notes that worm castings refers to worm manure specifically, while vermicompost involves a mix of worm castings, partially composted food scraps and resistant materials that take a long time to break down.

Features

Worm castings look like small black specks, similar to coffee grounds. Vermicompost often looks like coffee grounds mixed with small pieces of bedding, such as paper or cardboard, resistant materials such as avocado pits and tiny pieces of plastic from shredded envelopes, and tough food materials such as woody and incompletely decomposed broccoli stems.

Considerations

The purer the vermicompost is, such that it consists mainly of worm castings, the higher its commercial value. No standards exist however to measure or label vermicompost on its level of purity, Christie notes, which can be measured by the look and feel of the material and its effectiveness at boosting plant growth.

History

The pioneer of using red wiggler worms, Michigan biology teacher Appelhof, provided one of the earliest and most widely accepted definitions of worm castings in her 1982 book "Worms Eat My Garbage." A casting "is the material deposited after its moved through the digestive tract of the worm," she wrote. Vermicompost contains worm castings, as well as "partially decomposed bedding and organic waste."

Fun Fact

Some people also confuse the terms vermicomposting and vermiculture. Vermicomposting is the process by which worms convert organic wastes into compost, notes researcher Glenn Munroe in "Manual of On-Farm Vermicomposting and Vermiculture." Vermiculture is the culture, or raising, of earthworms. The goal of vermiculture is to increase the number of worms either to expand a vermicomposting operation or to sell to customers.

Expert Insight

"There is often considerable debate about defining the differences between castings and vermicompost," notes biology professor Rhonda Sherman of North Carolina State University. While some worm producers use the terms interchangeably, "others prefer to differentiate between materials that pass through the worms (castings) and that which includes all composted feedstocks (vermicompost.)"

References

• "Worms Eat My Garbage;" Mary Appelhof; 1982
• Red Worm Composting: Worm Castings vs Vermicompost -- Whats The Diff?
• "Manual of On-Farm Vermicomposting and Vermiculture;" Glenn Munroe, Organic Agriculture Centre of Canada; 2007
• "Biocycle"; Latest Developments in Mid- to Large-Scale Vermicomposting; Rhonda Sherman; 2000