Vermiculture: Reduce Your Manure through Worm Composting
Authors: Jenifer Nadeau
Jenifer.Nadeau@uconn.edu
Reviewer: Debra Hagstrom, Extension Specialist, Illinois Extension
Publication EXT130 | July, 2025
What is Vermiculture?
Vermi is the Latin for worm. Vermiculture is the use of worms to break down organic wastes in compost and decaying matter. Worms break down the organic matter via their digestive processes. These earthworms are a specific type known as red worms, tiger worms, or red wigglers (Eisenia spp.).
This fact sheet will discuss the use of worms and other beneficial insects, such as nematodes and praying mantises.
Advantages of Vermiculture
Vermiculture composting has several advantages:
- It can reduce labor and equipment costs of regular composting in windrows, since there is less need for aeration;
- There are no nitrogen costs since supplemental nitrogen is not needed;
- There is no unpleasant odor since it is an aerobic process;
- Worm castings (worm feces) improve plant growth even more than regular compost;
- Worms will double their population every four months, under ideal conditions;
- Dramatically speeds up the decomposition process, resulting in quicker time to a useful product.
Disadvantages of Vermiculture
There are some disadvantages of vermiculture:
- Initial cost of red worms may be cost prohibitive (up to $22/lb for bulk orders plus shipping);
- Need to care for and monitor worms year-round;
- Decomposition depends upon the number of worms in the pile;
- The market is less developed for worm castings than for regular compost;
- Weed seeds or parasites may not be killed using this method.
How to Use and Manage Vermiculture
One horse produces about 350 lbs of manure per week. One pound of Eisenia (approximately 1,000 worms) will eat approximately 3.5 lbs of material per week. So, you will need 100 pounds of Eisenia per horse to digest each week’s manure.
If the manure is mixed half and half with worm bedding, 200 lb of Eisenia will be needed per horse. Start with as many as you can afford and slowly double the population, but you do not want to overwhelm the worms with too much compost. Start small and increase when you have more worms.
Most vermiculture users employ either a worm bin or a windrow method. A worm bin would be for a smaller operation, and will be more management-intense than a windrow method. It may be possible to add worms to a manure pile as well, but there is no literature on this method.
The directions that follow on worm bins come from Earth911. Worm bins are usually eight to 16 inches deep, with one square foot of surface area per pound of compost or worm bedding, per week. Adding at least some worm bedding on a regular basis is important to keep the worms productive. Good bedding must be free from sharp or abrasive material that may harm the worms’ sensitive exterior, retain moisture, allow oxygen flow, and be of neutral pH.
Use a mixture of materials to create a balance, or stay with the same material; you don’t necessarily have to add things from the list below. Worms may eat up to 50% of their bedding. Most vermicomposters should be adding bedding more often. There’s no particular ratio, it’s more of an art than a science.
Other Worm Bedding Additives
- black and white newspaper torn into one-inch-wide strips and moistened to the dampness of a wrung-out sponge;
- leaves that are broken up as much as possible and kept from matting together so that air can circulate through the pile sawdust used in a method similar to the leaves;
- a handful or two of soil;
- ground limestone, or crushed eggshells for grit and calcium;
- peat moss;
- coconut husks (coir);
- torn up cardboard;
- shredded paper (added every few months, process it like the newspaper above).
Besides manure, worm food you can add includes:
- stale bread
- fruit and vegetable scraps
- coffee grounds and filters
- non-greasy leftovers;
- grains;
- tea bags .
Do not feed the worms:
- meat;
- cheese;
- yogurt;
- fish;
- butter;
- oily foods;
- plastic bags;
- other plastic or metal;
- pet waste (dogs, cats, hamsters, etc.).
Cover the food with worm bedding after you have added it. Place the bin in a shady location where it will not freeze or overheat, such as a garage, patio, or outside the back door of the barn.
Keep bins out of hot sun or heavy rain. If temperatures drop below 40° F, move bins indoors or keep well-insulated outdoors. Begin feeding the worms only a little at a time. As they increase in number, add larger quantities of manure and food. That is all that is needed for maintenance.
After three to six months, the bedding or manure will have been eaten and you can begin to harvest the brown, crumbly worm compost. It is necessary to do this at least twice a year to keep the worms healthy.
Harvesting Techniques
There are four possible methods for harvesting when using worm bins:
- Move the contents of the worm bin to one side, place fresh manure and bedding materials in the newly created space. Harvest the other side once the worms have migrated to the new food and bedding.
- Add the worm compost to your garden soil by removing one third to one half of the contents of the bin, including the worms. Add fresh bedding and manure to the bin.
- Spread a sheet of plastic out in the sun or under a bright light. Dump the contents of the bin into a number of piles on the plastic. The worms will crawl away from the light into the center of each pile and you can brush away the other material on the outside by hand.
- Place a decomposing melon on one side of the bin. The worms will go to the melon.
- Place food scraps in an onion bag and the worms will enter the bag to reach the food and then remove the bag.
According to the fact sheet by Colorado State University (Card et al. 2002), with the windrow method you can use one of two options, Option 1:
- Create an initial manure base six-feet wide, 18 inches tall, and six-feet long oriented east/west so it receives sunlight on the south side all day and wet it so that the moisture content is wetter than a wrung out sponge.
- Divide the worms and spread them evenly over the top of the moistened base material; they will migrate into the material. Then add a three-inch layer of worm bedding and manure weekly to the start-up pile and moisten as before.
- After the pile reaches a height of three feet, add new worm bedding and manure to the end of the pile in the direction that the windrow will be built, matching the height of the startup pile and with a height of three feet and turn or water it to facilitate a maximum temperature of 145° F.
The worms will move into it once it has cooled to 90° F and has ideal moisture levels. Continue lengthening the windrow until out of space, then you can U-turn back parallel to the first windrow.
The advantages of this option are that it involves less hand labor, the worm population grows more rapidly, and there is pathogen and weed seed reduction. The disadvantages are that there is a higher chance of the windrow becoming dangerously hot and digestion is not as complete.
Option 2 is to:
- Create an initial manure base six feet wide, 18 inches tall, and six feet long oriented east/west so it receives sunlight on the south side all day and wet it so that the moisture content is wetter than a wrung out sponge.
- Make it as long as six weekly volumes of material will allow. Divide the worms and spread them evenly over the top of the moistened base material; they will migrate into the material. Allow the worms to colonize the windrow and digest most of the base material (time required depends on number of worms).
- Add water as needed to the proper moisture content and monitor for digestion. Then add a three-inch layer of material on top of the base layer down the length of the windrow and moisten as before. Make additional three-inch layers at a frequency determined by how quickly the worms digest the material.
- After the first windrow reaches three feet in height, build the second base layer parallel to and touching the first windrow. Then add a three-inch layer of material on top of the base layer down the length of the windrow and moisten as before.
- Add more layers as the worms digest the material.
The advantages of this method are that there is less of a chance of the windrow becoming dangerously hot and there are more castings with more thorough digestion. The disadvantages of this method are that more hand labor is involved and the worm population does not grow as rapidly.
To harvest the castings from the windrow method, check to be sure that worms have migrated into the new material and till the castings directly into the soil or screen it to add it to pastures, soil mixes, potted plants, lawns, and gardens.
Where Do I Get the Worms?
There are many online sources for Eisenia. Do an internet search for red wiggler worms, red worms, or tiger worms. You may already have them in your manure pile or compost bin.
Are Worms Temperature Sensitive?
Eisenia prefer temperatures of 65° to 75° F, but can tolerate temperatures from 39° F to 90° F. Eisenia fetida and Eisenia andrei were proven in Colorado to withstand near freezing conditions, making them the best choice for outdoor vermicomposting. At higher temperatures, make sure the worms do not dry out. In freezing temperatures, leave the worms alone.They will migrate to the most comfortable areas for them in extreme temperature conditions, hot or cold. Cover the pile with insulating materials such as old blankets, vacuum cleaner bags, sheep’s wool etc. for the worms. Feed them at reduced levels in the winter but do continue to feed them.
Will Deworming Products Negatively Affect the Worms?
No, dewormers are deactivated up to 95% after passing through the horse’s digestive tract and are further deactivated by sunlight so dewormers should cause minimal to no harm to the worms.
Warning Signs That Worm Composting is Not Going Well
- Worms are dying;
- Bin/windrow smells rotten and/or attracts flies.
Causes of dying worms may include (solutions in parentheses):
- Worms may not be getting enough food (bury more food into the bedding);
- Worms are too dry (moisten pile to wrung out sponge level (40% moisture);
- Worms are too wet (add bedding, gently mix the bedding);
- Worms are too hot (put bin in the shade);
Causes of bin/windrow smelling rotten and/or attracting flies may include (solutions in parentheses):
- There is not enough air circulation (add dry bedding under and over the worms and do not feed them for two weeks);
- Pile contains non-compostables such as meat, pet feces or greasy food (remove these);
- Exposed food is in the bin (secure the lid, cover food scraps with bedding, and cover worms and bedding with a sheet of plastic).
Uses for Worm Compost
Worm compost can be used as a fertilizer and soil amendment. Add it to soil mixes, pastures, potted plants, lawns, and gardens.
The Use of Beneficial Nematodes
On a horse farm, the most likely application of beneficial nematodes would be to kill fly larvae and ticks.
Apply them early in the morning or at night. Wet the soil first, then apply them by mixing them with water and using a watering can, irrigation or mist system, hose end sprayer, backpack or pump sprayer.
Once they find the pest, they will enter it through a body opening or directly through the body wall. The nematode will then release a toxic bacterium which will kill the host within 24-28 hours.
This bacteria will provide a food source for the nematodes, allowing them to reproduce until the food resources are depleted, at which time they will exit the dead host and immediately look for a new one.
A common nematode variety used to kill fly larvae is Steinernema carpocapsae and Steinernema feltiae to kill ticks.
Using of Praying Mantises
On a horse farm, the most likely application of praying mantises would be to kill mosquitoes, along with mites (which can be an intermediate host for internal parasites).
When you order praying mantis, you will receive egg cases that you attach to the branches of shrubs, trees, or other plants, at a notch between the stem or trunk and a branch in a warm location, out of sunlight. Or you can hatch them in a paper bag kept in a warm place. The praying mantises will consume the mosquitoes and mites once hatched. However, they will consume each other as well as other beneficial insects if enough pests are not available. They do not consume ladybugs since those are bigger than most other beneficial insects.
Use of biological methods to manage manure and insects can be very effective. Worms can help reduce waste on the farm. Beneficial nematodes and insects can be an effective means of insect control. Use of these environmentally friendly tools can make your farm more enjoyable for you and your horse(s).
Resources
Arbico Organics. http://www.arbico-organics.com/category/beneficial-insects-organisms
Card A.B., Anderson J.V., and Davis J.G. Vermicomposting horse manure. Colorado State
University Cooperative Extension Fact Sheet no. 1.224. (2002) http://equineextension.colostate.edu/content/view/171/57/
Earth 911 (2007). Composting with Worms. http://earth911.com/news/2007/04/02/compostinghttp://earth911.com/news/2007/04/02/composting-with-worms/with-worms/
Elcock, G. City Farmer, Canada’s Office of Urban Agriculture. Basic Guide to Worm Composting. (1995) http://www.cityfarmer.org/wormcomp61.html
Manure Maiden. Ask the Manure Maiden. (2008) http://www.manuremaiden.com/blog/
Parson’s Archive, Texas A&M University. Home Worm Production. http://aggiehttp://aggie-horticulture.tamu.edu/archives/parsons/publications/worm/worm.htmlhorticulture.tamu.edu/archives/parsons/publications/worm/worm.html
Ruffner, Christy. Vermiculture Northwest: A Worm Farm. Composting with Worms. (2008) http://www.vermiculturenorthwest.com/
The Worm Ladies Rhody Worms. http://www.wormladies.com/pages/aboutourworms.html
Uncle Jim’s Worm Farm. What Can I Use for Worm Bedding? (2023) https://unclejimswormfarm.com/what-can-i-use-for-worm-bedding/ (Accessed 5/16/23)
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