How to Extract Worms from Vermicompost Beds

Vermiculture or vermicomposting is the production of compost using earthworms (vermi: latin for worms), specifically the species of worms that normally inhabit the surface litter (epigeic species) in the field. In vermicomposting, these species decompose organic material (under optimum conditions) in the top 4-6 inches of an earthworm bed or system.

Frog Hollow Farm has 3 earthworm beds (compost piles or windrows) in a field behind the old horse stables. Each bed has a length of 100 feet and a height of about 6-12 inches. The earthworms have been decomposing various residues for the last 1-3 months: fruits from the farm, kitchen residues from the Frog Hollow kitchen, horse bedding from a local stable

In the last couple of months in Brentwood, we experienced some very cold nights.  It was hard to separate the worms from the compost they produce because they were driven to the bottom-center of the beds by the cold.

However, recently we had a few nights and days that were much warmer and we were able to start collecting the worms and the compost because more worms had migrated to the top layers of the beds because of the warmth.

We also wanted to start collecting more vermicompost because next week new prune trees are being planted and we think that the vermicompost will have a positive effect on their growth.

We are considering the use of a combination of thermophilic compost and vermicompost on the farm this year. Thermophilic composting enables the sanitization of residues (high heat kills the seeds of weeds, plant pathogens and human pathogens) and the destruction of most plant toxic pathogens. Also, in thermophilic composting, woody particles are decomposed by the action of microorganisms (fungi and actinobacteria), some of which can act at low temperatures, some at high temperatures. Vermicomposting increases nutrient availability to plants, is much richer in hormones that stimulate plant growth, and has a much a higher diversity of microorganisms than thermophilic compost. Woody particles cannot be decomposed by earthworms but shredded cardboard is a worm favorite. Many studies have shown that good composts are rich in diverse organisms.

In summary, this week we started extracting earthworms from vermicompost in two 100-feet beds. This was achieved by passing the processed vermicompost through equipment with rotating screens set on a slope with a cone shaped unit at the end. The vermicompost is collected by the rotating screens while earthworms have a tendency to adhere to the metal surface at the cone shaped end and drop off into a collection. This equipment is called a trommel and is very simple to operate. The earthworms that are separated from the compost are re-cycled into new beds with more food.

- Christophe Kreis


Christophe Kreis MLF Soil Consulting PhD, Molecular Biology/Developmental Biology, University of British Columbia, Canada. Christophe is co-founder of MLF Soil Consulting with his wife Monique. He started his career in basic medical research and after various positions in academia and industry Christophe slowly returned to his first passion Soil Ecology and Microbiology. It is his belief that human health is tied intimately to soil health through the production of healthy food. For this reason MLF Soil Consulting is committed to help farmers improve the management of their soil through composting, vermicomposting and biological analysis of microbial soil life.

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