C:Nhoosing Your Mulch? Think of the Fungi.

Ideally we want a diverse range of mulch and C:N ratios such that we get a diverse range of biology. I’d wondered what that range might be so did some digging, or should that be mulching? Here’s one paper.

Effects of carbon concentration and carbon to nitrogen (C:N) ratio on six biocontrol fungal strains are reported in this paper. All fungal strains had extensive growth on the media supplemented with 6–12 g l−1 carbon and C:N ratios from 10:1 to 80:1, and differed in nutrient requirements for sporulation. Except for the two strains of Paecilomyces lilacinus, all selected fungi attained the highest spore yields at a C:N ratio of 160:1

Effects of carbon concentration and carbon to nitrogen ratio on the growth and sporulation of several biocontrol fungi

Seems to confirm that for fungi to reproduce and sporulate, that they need a constant supply of carbon. Note that the study only went to 160:1, and more carbon could be more desirable.

If you look at this chart I made, the curve is steepest at the peak between about 18:1 and 50:1, this range seems likely to be the sweet spot for fungi and for soil carbon priming, however to reproduce fungi, material with a higher C:N is also desirable.

fungi vs c:n.png


Supercharge mulch using this basic principle

eat your garden

This guy gets it.

  1. Add high nitrogen greens with the high carbon mulch,
  2. Wet/soak the lot,
  3. Mix a little to cover it all with microbes.
  4. Keep adding moisture.
  5. Soil profit!

You can also premix the mulch with greens and a handful of soil and soak in a container to ensure the mulch absorbs the water and adsorbs the microbes.

Soaking mulch in watered down 5:1 aged urine also adds nitrogen and other minerals, remember to add some soil for microbes.

Mulch! The Soil Carbon Continuum Way

Matt’s video prompted this reply. 🙂 Now you may know my views on compost, well…

In the video above they show a comparison of the effect of soil imprinting on run-off vs not imprinting on the left. Soil imprinting is a wonderful way to start a garden if you don’t have much compost or organic matter in topsoil, say in a dry climate. Throw what compost you have in those troughs, or not. Soil imprinting simply makes your soil look like one big egg carton helping to collect rain and wind debris. Soil moisture is the single biggest factor when it comes to building soil carbon and fertile productive soils, living plants and the microbes they host in the soil are the other. Harvesting that water where plants can use it to suck carbon from the air and feed it to soil microbes is critical, but so is the material that blows into the troughs. This material is very nitrogen rich, like the air that blows it in, and tends to have a high cation exchange capacity. It’s why weeds thrive in cracks and crevices.
This is mulching in place.

Live in a wet climate? Try planting in the peaks.

Cattle, bigfoot and astronaut grazing systems have a similar effect to soil imprinting, this can be a useful feature in intensive rotational grazing systems, so long as you have enough astronauts…

soil imprinting.jpegcattle-footprintbigfootmoon-imprint

Once you’ve imprinted, simply broadcast seeds and what compost you have into the troughs where water and debris blown by wind and rain collect and away you grow.

And while compost is great and helps get plants and a garden get started, what really gets the party going after that is when you chop and drop or roll and crimp just when plants flower and reach peak biomass. Studies have shown you get 3x more microbial biomass carbon and nitrogen than from compost if you chop a cover crop. More if you roll and crimp it, and even more on sandy soils.

It’s the leaching of soluble compounds from fresh litter that helps achieve this by feeding microbes that glue soil particles together and make houses for themselves, along with the moisture management properties of the bulk material once soluble nutrients are leached. Rolling and crimping helps by slowing the moisture loss.

I’ve previously written that when mulching ideally mulch should have a C:N of less than 50:1 to prime soil carbon, otherwise until the soil interface layer with mulch has biodegraded enough it will have a negative carbon priming effect that leads to problems like nitrogen deficiency. Planting legumes can help here if you’ve made that mistake, so can running chickens over the mulch, or simply moving it aside to expose the soil to more air.


Ultimately, we should aim for the Soil Carbon Continuum approach that consists of increasing C:N and chip sized mulch layers. Increasing in chip size is similar in many ways to the soil imprinting above.

It’s not just plants that need layers in the permaculture world.

permaculture layers.gif

I like to start with soil imprinting, then compost, fresh plant litter, dry leaf/twig/bark mulch, branch mulch, sapwood mulch and then heartwood mulch layers. Each increasing in C:N ratio and halving the amount applied with each layer. All followed by a living root.


Because ultimately it’s the inputs that drive microbial diversity and power the soil food web, not the other way around. Fungi for example need a continuous supply of carbon to grow and fruit. In forests massive old growth trees do this in large quantities when they suck carbon from the atmosphere. It’s been shown that adding nitrogen fertilizer disrupts this feeding of soil microbes by trees, upsetting the highly tuned ecosystems.


So don’t forget the living root in those layers above. They host symbiotic microbes like mycorrhizal fungi that can shunt nutrients and water at 3mm per hour, that’s 72mm or 3″ a day!

mycorrhizal fungi.jpg

root soil carbon exudates.jpg

And roots pump the carbon in the air into the soil to feed soil microbes, but only up to a point. What’s that point I hear you ask? It’s soil moisture dependant. It’s been shown that plants exhale more carbon than they sequester when when moisture deprived during droughts. And increasing carbon in our atmospheres means plants thirst for more water leading to even worse droughts in some climates as plants suck that water up.

living root.jpg

That’s it. Follow the path of the living root.

In another post I’ll cover some different forms of carbon that make up the soil carbon continuum and play different roles and why we want diversity there too.

Mulch Decomposition Rule of Thumb

I made a chart and in the process learned that as a rule of thumb mulch C:N more or less follows an exponential time decomposition rate for carbon. Your decomposition time will vary depending on location temperature, latitude etc.


I based it on carbon decomposition rate data I could find, and Australian Native Forests and Plantations.

My conclusion is;

  1. build soil with with grass/legumes/compost/green leaves in the first year.
  2. add leaf litter in the second year.
  3. add twig & bark in the third year.
  4. add branch in the fourth year.
  5. add sapwood in the fifth.
  6. add heartwood in the sixth.

Basically; grow to chop and drop and by year 7 your soil will be awesome.

Kurapia, The Drought Tolerant Ground Cover – Dog Approved

California Garden Girl

Drought Conditions Trial
Kurapia was included in a 2012 University of California at Riverside study that evaluated the performance and appearance of 19 turfgrass species or cultivars in drought conditions.  It performed best along with Kikuyugrass and buffalograss, two warm-season turfgrasses.  Click here for a full report of the study.

Hot Compost, Cold Compost? Not Compost. [Rant]

Hot Compost => Compost

Cold Compost => Biodegradation

Vermicompost => Vermicasting? But they’re not just castings => Organic Matter?

In my world, composting requires a certain temperature for it to be called compost. If it’s not hot it’s not compost, then it’s biodegradation. Composting is just biodegradation at a certain temperature for a certain amount of time, usually with the aim of killing off “pathogens”. Gah. because all pathogens don’t like it hot right? Ugh. It’s like the anaerobic vs aerobic pathogen argument, don’t get me started on that.

Vermi and compost make no sense together either, neither does cold and compost, yet everyone is doing it and sucking me in with their hot compost beliefs.

Biodegradation can happen at cold or hot temperatures.

Composting kills off microbes that don’t like it hot, that’s a given. How is that good for microbial diversity and plants that grow at ambient and not hot temperatures? Because you kill off some plant pathogens at those temperatures? At what cost?

Sure compost breaks down more things and faster, however people seem to place it on some pedestal. All that heat is just energy going up as hot air! Composting sends a lot of the matter and energy into the atmosphere. It also requires a heaped pile to keep the temperature high, and a concentration of materials is a great way to create pollution in the form of leachates in the one place too, especially when rained on. Raking or collecting materials for a pile might give you a nice clean garden but it also means less ground cover that could be providing multiple benefits to the soil too! But it’s neat, it’s tidy! It’s organised and sanitised! It doesn’t attract creepy crawlies.

Compost, what is it good for? Absolutely some things.

But not others.

I’d rather most materials were mulched and left as ground cover to biodegrade at ambient temperatures where possible. Whether that be plant litter chopped and dropped by plant or animal, or a hole dug and organic material buried. Organic litter feeds soil, it helps manage temperature, moisture and microbes. It’s a house and a job for the homeless all in one, the best kind of help those on the fringe can get with services like water to boot!

Mulch everything. Vermiculture, Ferment, Anaerobically Respire, Compost or Pyrolyse what doesn’t biodegrade at ambient temperatures.

Composting should be one of the last resorts, not the first.

Growing and feeding living mulch should be the first.

Maximising photosynthesis in order to create more mulch to maximise photosynthesis!

Feedback loops. The Green, and Red, and Purple, and Psychedelic Rainbow.

Not brown.


If it’s brown, thumbs down.

bare soil.jpg

If it’s bare, *death stare*


Down with compost piles!

And spread them around.

Let them slowly feed and nurture plants and soil, not themselves.

Formation of soil organic matter via biochemical and physical pathways of litter mass loss : Nature Geoscience : Nature Research http://www.nature.com/ngeo/journal/v8/n10/full/ngeo2520.html




Gardening with Organic Mulch [+Rant]

What he’s practising is excellent, however I felt I needed to make a few comments, firstly on the use of the word aggradation and then a few other terms.

I believe the word he wants is aggregation, which is what soil microbes do by aggregating soil particles with mucilage and exudates to build soil aggregates and structure as they move through it. Aggradation however is the formation of soils by geological process, like wind, rain, and the movement of water causing sediment accumulation. It is often caused by soil degradation through poor land management practices such as tillage.

Also, a more appropriate title for his clickbait would probably be Gardening with Organic Mulch, as I’ve titled it here. As decomposing plant residue is considered an organic fertilizer by many. Ramial chipped wood is just one form of mulch, and not always the best form for every application or soil. It is excellent for building soil however for subsoil application material higher in nitrogen will feed microbes more of what they’re made from and build soil faster if the soil moisture and environment are adequate.

I believe the fungi that break down the ramial chipped wood and other organic matter are collectively known as saprophytic fungi, Basidiomycota mentioned are just one division of that family and of the larger that make up the Saprotrophs, which include other microbiology, fauna, plants and animals. Holistic approaches use all of these to build soil for differing plant needs.

Ramial chipped wood tends to be high in potassium and low in phosphorus, why fungi love it. The high carbon content also buffers soil pH and moisture which they like. Just add water.

The fastest ways nature builds soil organic matter is actually in prairies and grasslands with high rainfall, not forests. Protected seagrass bays are even more productive than these and contain the highest amounts of soil organic matter recorded to date. These areas maximise photosynthesis and nutrient runoff from higher elevations and tides, and in native grasslands the long thin root perennials sequester carbon, the building block of all organic matter, deep within the soil profile where it isn’t easily oxidized and will live for centuries to millennia. Fungi also store carbon inside of soil microaggregates preventing their oxidation by other organisms that would release it as atmospheric gases. Releasing these gases isn’t always bad as plants can feed off these higher concentration atmospheric gases created by the soil biology to increase productivity and sequester more, but only if the soil moisture and environment is adequate.

I keep repeating soil moisture because it has been shown to be by far the most important factor in building organic matter in native soils. And ramial chipped wood in moderation is certainly an excellent way of managing soil moisture while also fertilizing. It covers soil, it hold moisture, it fertilizes.

You will however not get Back to the Garden of Eden with just wood chips!

Wood chips reduce photosynthetic land productivity when not planted out!

A more holistic approach is needed to solve for these!

Now I’m tempted to start my own growing movement and calling it Holiculture. 😛