C:Nhoosing Your Mulch? Think of the Fungi.

Ideally we want a diverse range of mulch 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

mulch-decomposition-rate

Ideal Soil Element Ratios

There’s no such thing as ideal. Or is there?

While calculating the ratios of soil elements I made an interesting observation about carbon. Both plant and soil.

We know from previous studies that about 8% soil organic carbon (SOC) is optimum for yield. It turns out that’s about the same amount of carbon in most plants. Coincidence? I think not.

Optimum soil carbon for yield likely correlates with actual plant carbon.

If I take that and assume an 8% SOC 10cm topsoil and a linear decline over 60cm depth, I get 15.75% Total SOC. You see these levels in some forests and Terra Preta.

I wonder what percentage of fungi and bacteria is carbon?… Just checked… and it turns out fungi are about 8%!

*Mind Blown*

Spirulina, a cyanobacteria? 3.12%. If you divide 8% by 3.12% you get a Fungal to Bacteria ratio of 2.56:1.

Meaning you’d need 2.56 fungi to 1 bacteria to get the equivalent of 8% carbon.

What did David Johnson say was ideal Fungi:Bacteria ratio? Well, will you look at that, 2.56 is pretty darn close to the productivity maxima.

So, depending on what you are growing, it could well dictate the ideal soil organic carbon and the bacteria:fungi ratio.

FWIW, if you’re growing a human, then we’re 18.5% carbon… and a vegetarian would need to consume something like 2.3x the amount of food as a carnivore. This is below the bifurcation growth rate of chaos theory at 3.0.
Fungi:Bacteria Ratio.png

15.875% Total SOC.png

8-soc

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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. 😛

Hieronymus_Bosch_-_The_Garden_of_Earthly_Delights_-_The_Earthly_Paradise_(Garden_of_Eden).jpg