When Is Manure Ready For Vermicomposting?

Interesting question from Katheem:

“…[Are] there any parameters such as colour,
texture, state, C:N ratio etc.. to identify the ideal cow dung/manure
for vermicomposting?”

Hi Katheem,

There are definitely some attributes you can look for when it comes to working with ANY type of manure. For starters, it’s important to mention that there is a big difference between using manure as a starter “habitat” material, and using it as a “food” material once that safe habitat as been established.

Generally speaking, habitat material will need more time/handling than the manure designated as food. Fresher manures tend to contain higher salt levels and have a greater tendency to off-gas ammonia (both of these commonly influenced by urine content). Salts and ammonia are very dangerous for worms, even at very low levels.

Starter Habitat Manure – If you plan to actually start up a worm bed containing a significant proportion of manure, you will definitely want to make sure it is really well-aged. Ideally, it will have been sitting in an outdoor location, exposed to the elements, for a month or more. It should be darker in color than fresh manure, and should have NO manure (or ammonia) smell – if anything it should be earthy smelling. It will tend to have more of a uniform appearance, not unlike that of a compost or garden mulch (obviously depending on the type of manure, and bedding materials – if any – that were mixed with it originally).

Food Manure – Once you have an established safe habitat – the larger the better – it won’t be quite as important to age manures before adding them to the system. There are definitely some caveats to mention here, though. For starters, the system will need to be extremely well ventilated – best if completely open in fact. This way, any ammonia that gets released can escape without harming the worms. On a related note, the manure should also only be added in thin layers on top – it should NOT be mixed into the habitat zone. Apart from the potential ammonia concern, mixing the manure in may create hot spots in the system which can also be a hazard for the worms.

Another important consideration will be the salt content of the manure. If it has not been allowed to sit outside exposed to the elements, or at least soaked and drained, there is a good likelihood that there will be an accumulation of salts in your system over time – which will also create issues. Certain types of manure – such as poultry manure – can be especially tricky to work with for this reason.

If you have a fair amount of outdoor space, you might try something like a “walking windrow”. Start by setting up a simple heap of well-aged (“habitat”) manure, and introduce the worms to it. Once they are settled in, simply add fresh manure to one side, gradually extending it out into a windrow over time. If the windrow is exposed to the elements, that’s basically all you need to do (apart from harvesting worms/compost if/when you choose to do so). If protected from the elements, you may want to soak each new manure deposit down really well so as to help flush excess salts out.

Additional Manure Use Tips

  1. Bagged manures you buy from garden centers etc are typically NOT going to be a good choice, since they tend to be pretty lifeless and can be high in salts.
  2. Avian manures (from any kind of bird) are very different from farm mammal manures – they tend to give off a lot of ammonia and contain high levels of salts. They also tend to be very dry initially, making it even more important to let them sit outside for a while before use.
  3. Liquid manures, such as pig and dairy cattle manures, should be mixed with a carbon-rich, absorbent material such as straw, saw dust, shredded cardboard etc and allowed to “pre-compost”, or at least age, for a period of time before use (how long will depend on your intended use, as discussed earlier).
  4. When using ANY type/source of manure for the first time, always test on a small-scale before going too crazy with it.
  5. Aside from helping to make manures more “worm-friendly”, pre-composting can be a valuable practice for killing off weed seeds and any pathogens that might be in the original material.

Hope this helps!

Recommended (Related) Reading
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    • joe
    • July 9, 2014

    Thanks again Bently for another well explained question

    • Katheem
    • July 14, 2014

    Hi, Thanks for the immediate response. I really appreciate.

    I want to know how to spot the differences between fresh and old cow manure?. Apart from color and state. Is there any chemical parameters or fixed regulations for good cow manure to obtain good and maximum yield?. Does the feed has any role in it?. For example, if we are culturing Eisenia fetida, What kind of cowdung, from which source (feed for cow) and how many days old cow manure can be used.


    • Bentley
    • July 15, 2014

    Hi Katheem,
    I’m sure there must be a range of scientifically testable parameters for determining the stage of decomposition a given manure is at. But for most people this really isn’t going to be helpful or remotely practical. This is why I offer very simple guidelines.
    Your best bet for getting maximum benefit from cow manure would be to set up a system where you can add the manure fresh – the “walking windrow” method described above being a prime example. This way the worms will start feeding on it as quickly as it becomes “worm-friendly” and you won’t be left guessing if your manure is “ready”. As for food source, that can certainly have an impact on the quality of the manure – but I don’t know of any scientific studies that have tested this.

    • Katheem
    • July 16, 2014

    Thank you 🙂

    • Sarah
    • February 21, 2015

    I would just like to know the ratio of worms to compost material, meaning how many worms should we have per pound of compostable material. Also, how long will it take the worms to break down the material into usable soil?

    • barbara ingram
    • July 5, 2015

    i keep getting magnets in my worn container,how can i prevent this.

    • Bentley
    • July 16, 2015

    Sorry for the delay responding!

    Sarah – unfortunately my goto response of “it depends” definitely applies here. My preference is to let worms grow into a particular system rather than trying to maximize things right out of the gates. You’ll have a far greater chance of success. In other words, I’d suggest starting with FAR more material than worms – and make sure the initially habitat material is very well aged (I’d even test a small amount in a separate system to be safe).
    Barbara – I’m guessing you mean “maggots”. If your system is outside – especially if you happen to live in a warmer region – these are likely Black Soldier Fly larvae. They thrive in composting systems. My recommendation would be to add less food and more bedding to help out the worms. But in these outdoor systems it can be pretty tough to avoid some of these other larvae altogether. The good news is that as long as you are meeting the requirements of the worms (in terms of temperatures, moisture etc) these other critters shouldn’t cause any problems.

    • Heather
    • August 6, 2015

    I have someone wanting to pickup some rabbit manure to use for worm food. He asked about any medications, which wasn’t a problem. Do you know if neomycin sulfate is toxic to worms? I don’t want send any that might cause him any problems.

    • Bentley
    • August 7, 2015

    Hi Heather,
    I am not familiar with that one but it seems to be an antibiotic, so you definitely wouldn’t want too much of it in a worm composting system since it will have a very negative impact on the (important) microbes. I don’t think it would harm the worms directly, but they have an important microbe ecosystem in their guts so it may cause harm indirectly.

    • Jatin
    • January 7, 2017

    Is there any other source required with cow dung as nutrient source? I have given only cow dung as food source for worms. It will work or not?

    • Bentley
    • January 10, 2017

    I would used manure that has been mixed with carbon-rich material (like straw for example) and then allowed to hot compost for a bit (maybe a couple of weeks if well-controlled, longer if just sitting in big outdoor heap). Cow manure likely has all the nutrients the worms need, but on its own (especially fresh) it can cause harm (ammonia release, salts etc).

    • RandyLand
    • September 21, 2017

    G’day, I have a heap of cow and goat manure and straw that’s been cooking up all summer. It’s cooled down significantly but there’s still a very tiny bit of steam coming out of the core if I stir it up. My plan is to load up a few 35 gallon smart pots as worm bins in my basement over the winter. If i take the cool composted manure from the outside of the heap, will this be sufficient food for the worms? I have about a cu yd of this stuff.

    • Chris
    • March 31, 2018

    I had more than 100 worms, too many for my container, so I split them up. Checked on them a week ago, and shocked to find only ten??? They could not climb out so I assume they are dead, I did spot a few stick-like corpses, but really only 4 or 5. They only got fed cabbage leaves, bananas and coffee grind, but I did mix a bit of soil in with the worm compost.
    Also – the produced compost, can that be used as is, or must it be mixed with soil or other matter?
    Many thanks, I am a fairly new Wormy, still learning.

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