Fungal Compost

Making a more fungal compost has been an aim of mine for some time. One of the ways that I do that is to not make ‘hot’ compost, keep the proportion of high carbon materials high, and to not turn unless it’s needed. However recently I set up a truly fungal mix of ingredients and this post is about how that went.

 Why make a Fungal Compost?

I first started thinking about making a more fungal compost after starting to make actively aerated compost tea. Some of the compost tea recipes call for a fungally dominant compost, and the forums were full of ideas of how to make that happen.  I made leaf mould, and really good compost, but recently I’ve been thinking more about building my soil fertility without compost.

Soil Fertility without compost

I have been continuing to learn more about soil. How it works, how nutrients are cycled, and what drives these processes. I keep coming back to an idea that when I compost I’m not building soil fertility, merely redistributing fertility that has already been made. If I make a conventional compost I am mixing carbon and nitrogen rich materials in a ratio of around 30:1. By the time that the compost is ready the ratio has dropped to around 10:1, meaning that 2/3rds of the carbon has been lost. Now many of the cycles in soil work both ways. A good example of this is Nitrogen. It is both fixed and lost from the soil, but which of the two is prevalent depends on the carbon:nitrogen ratio in the soil. It takes energy for microbes to fix nitrogen, so if there are supplies of useable nitrogen in the soil, the nitrogen fixers use it, along with other soil life. It is only when the ratio of carbon to nitrogen increases that significant amounts of nitrogen is fixed by microbes. The phosphorous cycle works in a similar way. If the ratio of carbon to phosphorous is 200:1 or less, available phosphorous is bound up and becomes unavailable to plants. At a ratio of 300:1 or higher, microbes make available phosphorous that is bound up. Inbetween these figures both processes are taking place. Taking these into account, adding compost at a ratio of 10:1 doesn’t make sense. I will be doing the work that microbes in my soil could be doing instead.

Growing Carbon

If the key to building my soil fertility is carbon I need to do two things.The first is to produce the carbon, and the second is to ensure that the microbes that I need to utilise that carbon are present in my soil. The grain polycultures that I am growing will produce the carbon, both in the form of cellulose rich, lignified straw, and from root exudates. The point of the fungal compost is to ensure that the microbes that I need, predominantly fungi and actinomycetes, are present to deal with the raw materials that I will provide. The picture below is from one of my vegetable beds, and suggests that some of what I need is probably already there.

fungi in vegetable bed

fungi in vegetable bed

 Indigenous Microorganisms and Biofertilizer

Indigenous Microorganisms (IMO’s)

One way to get a wider range of microbes into my soil is to culture them. You can do that by collecting microbes from healthy environments, culture them, and then add them to the growing space. I used a version of the method described by Gil Carandang for making beneficial indigenous microorganisms, also known as Indigenous Microorganisms (IMO) in the Korean Natural Farming system. The next link gives a more accurate description of what I did (IMO). In fact I followed a cheat version as described in a series of youtube clips this is the first in the series.

The picture below shows the third stage, which is IMO3. What you can see is wheat bran that has been colonised by microbes that I collected on rice initially. As well as being added to my soil, some of this has been added to a special fungal compost mix which I’ll describe shortly.

fungal hyphae from IMO 3

fungal hyphae from IMO 3


Recently I started making biofertilizer. These are microbial ferments designed to convert minerals into plant available form. It’s a bit like replicating what would happen in the soil, but doing it under optimum conditions, and more concentrated. After repackaging the biofertilizers I poured the sloppy residue onto my fungal compost mix, and the picture below shows the result.

fungal compost in bathtub

fungal growth on compost

However I couldn’t determine whether the fungal hyphae were present in the residue, or came from the compost mix. The fungal hyphae are too small to see with the naked eye, but the picture below shows a fungal fruiting body present in the fungal compost.

fungal fruiting body in bathtub

fungal fruiting body in bathtub

Fungal Compost Experiment

I decided to try and identify where the fungus was coming from so I mixed some of the diluted IMO’s (IMO2 from the video series above), and added it to some wheat bran. I divided the bran into two containers, and added some of the fungal compost to one of the containers. From the other I took a handful of the bran and spread it on the top of the fungal compost. I left it for around five days. The pictures below show the results.

The first picture shows the bran only mixture. There are no visible signs of fungal hyphae, although there was some warmth from the center of the mixture.

wheat bran and indigenous microorganisms

Wheat bran with IMO3 mix

The picture below is of the bran mix that had some of the fungal compost added. All of the bran has been colonised. The broken texture is just where I wanted to check how far the mycelium extended. Only a small amount of the fungal compost was added. Less than 10%.

fungal hypha in wheat bran

fungal hypha in wheat bran

The picture below shows the bran spread onto the fungal compost mix. Wherever there was bran there was fungus. This makes it pretty clear that the fungus is coming from the fungal compost mix, exploiting a new food source. It also indicates that the mix is a really efficient way of inoculating bran, and then using the bran to introduce the fungus to the soil or container. However the bran alone may not be the best way of getting a wide range of fungi and other microbes into the soil, as it may only be colonised by a small proportion of the decomposers present. Using a wide range of fungal food sources will increase the range that can be potentially cultured.

fungal compost in bathtub

fungal compost in bathtub

My Fungal Compost

In order to get a fungal compost mix, I added a range of high carbon sources, many of them already colonised by fungi, to an old bathtub kept in an outbuilding. The primary source was some well rotted leaf mould. This would have had fungi that were able to utilise lignin as a food source. Lignin is the resistant material in wood, and stiff stems like straw. To this I added shredded miscanthus grass. This is a source of lignin and cellulose, like straw, but already mechanically shredded. With these two materials I included some of my best compost. This was a cold compost, made with lots of high carbon materials, and was two years old. After the batch was started I added some of the IMO3 bran and mixed it in. As the primary material that will be added to my soil is straw, I will continue to feed the mix with more straw-like materials. I would also like to add some more woody materials, perhaps some shredded branches. Eventually I will divide the fungal compost into smaller batches, mix them with straw and bran, and when colonised, add them to my vegetable beds, probably before returning harvested straw.

12 thoughts on “Fungal Compost

  1. philip

    Hi, I’ve read your posts with interest. I realize how little we really know about growing nutrient dense foods and healthy enriched soils. I’m curious about your thoughts about the utilization of beneficial indigenous microorganisms. What I’ve read suggests that much compost is bacteria rich but may not have enough fungi to build better soil over a long term. I’ve read Fukuoka and he wrote about hard the farmers had to work making and moving compost. His solution was to not plow and also to return all of the straw and other material (hulls, etc) other than seed back to the soil and he kept a cover crop on the soil all of the time. His way to make compost was really to “make it in place”.
    Do you foresee that your soil, once inoculated with your IMOs, and the resulting inoculated bran, that you will need continual additions of like material? Or, do you suppose that your soil will act like soil used for alfalfa; once inoculated it need not be reintroduced? I like the your idea of mixing many different cover crops for use (beans and grains, etc) since the end result will likely be soil that will contain a far broader range of fungi and micro-organisms.
    One of the chief problems for many of us is that we don’t have ready access to manures and commercial fertilizers are too expensive, damaging to the soil and of too limited use (short acting) to be of much help. I’m farming on nearly 13 acres of land that has been cultivated for hundreds of years and in my family for 150 years. Some of the land needs help from prior abuses and I’m continually looking for ways to improve it not using a plow since that is costly and damaging to the soil. I have some small plots that hadn’t been plowed, though hay removed, for over 50 years.

    Keep up your work; I find it very interesting.

    1. Deano Martin Post author

      Hi Philip
      I reckon that the fungi will be fine provided that the food supply is maintained. That is not likely to be a problem with the amount of straw that I am producing.
      All of the best


  2. rachel bailey

    Hello Deano
    I read your post with interest. I also have an interest in soil and the microorganisms within it; however, my knowledge of this complex ecosystem is somewhat basic.

    I have read that different plant types prefer different ratios of fungi to bacteria in the soil. For example, annuals (i.e., many of our vegetable crops) prefer a bacteria dominated soil (i.e., higher bacteria to fungi ratio) whereas perennial plants (e.g., trees, shrubs and herbaceous perennials) prefer a fungi-dominated soil (i.e., higher fungi to bacteria ratio).

    I wondered if you know or have any thoughts on:
    (1) what is the average ratio of fungi to bacteria in your fungal compost
    (2) what effect the fungal compost has on the fungi: bacteria ratio of the soil that you add your fungal compost to; and
    (3) what the effect of your fungal compost has on your annual veg?

    Many thanks

    1. Deano Martin Post author

      Hi Rachel
      Hoping to be in a position to quantify all of the above as part of my degree/postgraduate research. The bacterial-fungal ratio isn’t as clear cut as the examples that you gave, and many of the vegetables that I grow seem to thrive with the higher fungal content of my compost. My plan is to keep on increasing the carbon-nitrogen ratio in order to drive up th amount of Biologically fixed nitrogen and increase the availability of phosphorous, both of which are increased at higher levels of soil carbon.

  3. Séamus

    Dear Deano,
    I’ve just received my first post since I signed up for
    your blog, announcing your academic plans.
    As you will be even busier from now on, I’d better take the opportunity to pose the questions that I’ve being meaning to put to you for a while!
    I have followed your instructions for fungal compost,
    mixing the innoculated bran with compost materials ten days ago.
    When might I expect the compost to be ready?
    Is the process temperature dependent?
    Am I right to assume that batch size is immaterial with this method?
    In the absence of an old bathtub, I have used three covered forty gallon water tanks outdoors.
    Am I also right to assume that the innoculated compost can be used to start new batches, without the need for the bran innoculation stage?
    As I have reserved half the innoculated rice starter mixed with a similar volume of brown sugar, I am considering making another batch of innoculated bran at some stage for direct application to the soil around apple trees mulched with chipped branch wood.
    Have you tried using the bran in this way and has it made any appreciable difference?
    I appreciate the work you are doing and how much time it takes, I think your blog is a great service for those like myself who have similar interests but don’t have the time to carry out the research.
    My small scale grain growing was what led me to your blog in the first place but I am currently a very part-time gardener due to work commitments.
    All the best,

    1. Deano Martin Post author

      Hi Seamus.
      Temperature is an issue, along with moisture content.The type of material will determine if it is colonised, and how long it will take. batch size shouldn’t matter too much and your tanks should be fine.
      My attempt to innoculate a new batch of woody material has not progressed very far. I’m hoping to see an improvement when the temperature increases. It may have been better to use a bran/straw mix.
      I’m still quite new to this myself, so what you learn will be useful.

      1. Séamus

        Dear Deano,
        Many thanks for your prompt reply.
        My compost materials were from a garden maintenance dump at my workplace, lots of small branch wood & leaves among the compressed grass clippings.
        To this I added chopped rushes & some staw to open it out & also some horse manure.
        It was only mixed a few days before I put it in the tanks with the innoculated bran but already steaming, which it certainly had not been when I initially dug it.
        Not much signs of life since but still early days.
        The innoculated bran certainly had fungal growth in it & smelt promising!
        Your photograph of the bran colonised after five days on the surface of your heap certainly looked as though you were on the right track!
        I will keep you informed of developments.

        All the best,

  4. bob

    how about instead of buying wheat bran, have you use used coffee ground, its a free organic source for the fungus to grow on?

  5. tom butler

    hi deano
    really interested in soil microbiology, I have worked with compost teas, as well as biodynamic preperations. I’ve not come across the carbon phosphorous ratio before affecting phosphorous availability. I’m keen to learn more but a google search didn’t lead me to useful results. Can you suggest any links that are resonably easy to understand, thanks

    1. Deano Martin Post author

      Hi Tom
      Look in Soil Microbiology,Ecology and Biochemistry edited by E Paul. That’s my reference for that piece of information.

  6. Hiking Viking

    I’ve been looking for a home-version to make straw break down in hot compost faster or better. I understand that fungi (and some bacteria) break down lignin, but lignin is complex and resistant to decay except over a long period of time. My internet searches lead mostly to scientific papers and abstracts from researchers trying to just break down lignin and leave the cellulose so that it can be fermented into bio-fuels. It involves all kinds of complex chemical and biological processes. Lignin rules in high carbon materials such as straw and wood. I just want to make better compost, and hopefully, faster. The break down of lignin is one of the keys to doing that. Any ideas on how to encourage lignin break down straw compost without having to be a research scientist in the bio-fuels industry? My initial thought is to “pre-decay” straw so that when added to hot compost, it will decompose quicker. I think that would work, but I don’t know how to do that.

    1. Deano Martin Post author

      Hi David
      The straw breaks down pretty quickly in a heap especially if it’s shredded. Fungi, actinomycetes and cellulomonas all use it as a food substrate. As long as there is enough nitrogen and other minerals present there shouldn’t be a problem. Pre-soak in diluted urine for best results.
      Hope that helps.


Leave a Reply

Your email address will not be published. Required fields are marked *