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Worms for Composting Horse Manure

Here is a question from George:

My wife and I have two horses and 3 compost bins, each 8′x8′x4′. I’ve
been thinking that our compost might be significantly improved by
adding worms, so I’m wondering what your advice might be on this. We
rotate the bins, about 4 months each, so it takes about a year to
complete a cycle. The oldest bin is typically fairly cool, so I think
that it should be able to benefit from worms. Also perhaps bin number
2. Any advice on things to consider, such as the type of worms that
would work best, would be most appreciated.

Hi George,
Sounds like a great situation to me (said Bentley, green with envy! lol).
Pre-composting/aging the manure for a period of time is definitely important, but I honestly don’t think you would need to do it for as long as you have been, once you’ve got the worms involved. The material you have after the second bin is finished would likely be a great starter “bedding” for the worms, but I would likely set up some separate beds for the actual vermicomposting.

Assuming you have some room to do so, setting up long, low-lying windrow beds might work better for vermicomposting. Once you have the worms settled in the starter bedding materials you could likely start layering newer material over top. Rather than waiting even 4 months for the first batch, I’d suggest hot-composting the manure actively for 2 weeks to a month (tops) before layering it on the beds. Add perhaps 1-2 inches of the material every week or so (maybe less frequently early on, until your worm population has grown).

The best all-around choice for worms would be Red Worms in my humble opinion. They absolutely LOVE horse manure, so they will do every well in these beds, and help you to produce some very nice vermicompost.

During colder weather (assuming you get some where you are located) you’ll likely want to heap up the beds a lot more – maybe even keep the worms in one much larger heap of manure over the winter. The beauty of the “hot composting” process is that it will help to keep the worms warm and active.

Since you own these horses you will be very familiar with what sorts of “de-wormers” (if any) they are receiving, and what they are feeding on etc. For those of you who are getting your manure from someone else, my bottom-line recommendation would be to do your own due diligence before feeding it to your worms.

To learn more about the de-worming issue you may want to check out this older RWC blog post:
How Harmful are Vermicides in Manure?

Apart from the de-worming issue, there is also the potential for the presence of persistent herbicides. Thanks to RWC follower, Laurie S., for sharing these helpful links relating to the topic:

Killer Compost Reports
Use a Simple Compost Test to Avoid Contaminated Materials in Your Garden
Killer Compost Update: Herbicide Damage Still a Major Problem

Written by Bentley on March 6th, 2013 with 4 comments.
Read more articles on Reader Questions.

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4 comments

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Get your own gravatar by visiting gravatar.com John Duffy
#1. March 6th, 2013, at 9:49 PM.

3 8′ bins & 2 horses to supply them…Sounds like a beautiful combination.
Definitely, go with red worms!

Get your own gravatar by visiting gravatar.com Meranaldar
#2. March 7th, 2013, at 6:22 PM.

Those links at the end are rather scary, I hadn’t known about that.

Get your own gravatar by visiting gravatar.com Jennifer
#3. June 26th, 2014, at 3:07 PM.

How long should manure be aged before it can be fed to worms? And how to you harvest castings in larger worm compost piles?

Get your own gravatar by visiting gravatar.com Bentley
#4. June 30th, 2014, at 7:21 AM.

Jennifer – if manure is allowed to sit outdoors for a month or two it should be in good shape, but it really depends on the manure and on the environmental conditions. Horse manure, for example, can likely be “ready” for worms more quickly than this. Also – very important to note that the planned use will dictate the aging period as well. If it is going to be a base habitat material in a bed, you should age for longer. If a food material (once safe habitat established), it can be added basically “fresh” (assuming system with excellent air flow – and layering on top).

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