Gardening: The secret life of compost worms

When my Master Gardener friend, Bill Monroe, mentioned he wanted to gift his worm composter, I jumped at the chance to learn this technique. Here are some secrets I learned:

Vermicomposting is a “cool” process, versus the traditional “hot” compost pile that heats up organic materials to break them down. Give worms food, air, and a bed in the dark. In less than a month, a couple pounds of worms transform kitchen scraps from a small family of four into rich nutrients that plants can easily absorb.

By Phyllis Jachowski
Colorado State University Extension Master Gardener in Larimer County

Here’s what happens: By nature, worms eat through organic matter and soil containing microorganisms. Sticky mucous coats the mass during digestion and transforms the microorganisms into a rich nutrient in the worm “castings”. Worm manure is a super food. Studies show when 4 percent organic matter with castings is mixed with existing soil, more nitrogen is available to plants: 246 pounds/1000 sq ft with castings, compared to 161 pounds/1000 sq ft surrounding soil (The National Sustainable Agriculture Information Service; Sustainable Soil Systems).

Why use “red wiggly worm” workers? Many different types of worms break down organic materials. “Endogeic” worms live in upper soil layers in temporary burrows (“brown” worms you see in a shallow shovelful). “Anecic” worms live in deeper soil layers and drag organic matter down into permanent burrows (night crawlers, dew worms). The best type for vermicomposting are “epigeic” worms—surface worms with no earth burrows that eat decaying matter above the soil (red worms, “litter” worms). “Red wigglers” work the best.

Starting up:
1. Choose container: The box I inherited is a black plastic container (20”x23”x12”) with a loose fitting vented lid and side air vents. You could easily make one from wood or any dark colored tote. Some have movable racks that allow finished trays to be removed as worms eat into upper trays.

2. Gather supplies:
Bedding: shredded old office papers, newspapers or crumbled dry leaves
Water: a spray bottle is helpful
Peat moss or soil: 1-2 cups
“Red wiggler” worms: use about one pound worms/person in household
Food scraps: use one cup/per pound of worms. The best food scraps are fruit and vegetable trimmings. Use citrus and acidic fruits sparingly. Never use oils, meats or dairy products!

3. Stock box: Fill the box ¾ full with bedding. Sprinkle in peat moss or soil to help worms grind food (they have a gizzard, but no teeth!). Spray with water until the materials feel damp, like a wrung out sponge. Place red worms in bottom corner of the box, under the bedding. Bury food scraps in the bedding. Open the air vents. Put the box in a dark area indoors with temperature 40-70 degrees F.

4. Monitor frequently: Vermicomposting is a continual process requiring everything to be in balance. Occasionally stir, monitor moisture, and add food scraps. Keep it dark, or worms go on strike. Discard any liquid that collects in the bottom of the box—this is not “compost tea”! The liquid is leachate, waste from scraps that has no nutritional value and might contain unhealthy pathogens.

Be aware of things that can go south!
Food: Don’t overwhelm the worms. Go easy, or food will rot. (Guide: add 1 cup scraps per week/per pound of worms).

Water: Keep moist—if too dry, worms get sluggish and die. If their skin gets too wet, worms can’t breathe.

Air: Vent the box and occasionally stir. The worm box should be odorless. If it stinks, you have a problem.

Temperature: Worms work only in the dark between 40 – 70 degrees F.

Liquid in bottom of box: Throw away leachate.

Overpopulation: Keep an eye on your worms! During their one year life span, they double every 3-4 months, producing 2-4 hatchlings from lemon shaped cocoons the size of a wheat kernel. Start small. Compost is complete in 2-4 weeks: Finished compost, or humus, is dark brown and crumbly, smells earthy, and may have small undigested materials, but doesn’t resemble kitchen scraps.

Remove finished compost: Worms eat upward as they feed, leaving castings below. Push bedding and worms over to one side of the box. Remove the castings. Restock the empty side with bedding, soil/peat moss and bury food as before. Worms will migrate to food.

And the best part….what to do with humus! Adding humus to soil breaks up clay, improves water retention, increases air permeability, and provides nutrients. Top dress soil of established plants. Make potting soil using 1 part humus to 4 parts soil.

Consider making “compost tea”: soak finished compost in water 24-48 hours. Drain off liquid. Pour liquid directly on soil around plants, or spray on seedlings, plants and foliage.

Commercial vermicomposting: it’s a big deal. Humus is produced to improve soil. Worm composting is also used to detoxify soil and sewage sludge. Check online for regional and worldwide projects. Who knew worms do so much beneficial work!

For more information on earthworms and worm composting, refer to:
www.ext.colostate.edu/mg/Gardennotes/218.html “Earthworms”
www.ext.colostate.edu/ptlk/1622.html “Composting: worm composting”
Book: “Worms Eat My Garbage” by Mary Appelhof

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