Episode 248. Roots and Mycorrhiza

This is The ChangeUnderground for the week ending 8th of March 2021.

I’m your host, Jon Moore

Decarbonise the Air, Recarbonise the Soil!

The relationship between roots and mycorrhiza go deep, pun intended. From the site Mycorrhizal Applications comes the page “How It Works” [link in the show notes].


“Myco” – “rhiza” literally means “fungus” – “root” and describes the mutually beneficial relationship between the plant and root fungus. These specialized fungi colonize plant roots in a symbiotic manner and extend far into the soil. Mycorrhizal fungal filaments in the soil are truly extensions of root systems and are more effective in nutrient and water absorption than the roots themselves. More than 95 percent of terrestrial plant species form a symbiotic relationship with beneficial mycorrhizal fungi, and have evolved this symbiotic relationship over the past several hundred million years. These fungi predate the evolution of terrestrial plants, and it was the partnership with mycorrhizal fungi that allowed plants to begin to colonize dry land and create life on Earth as we know it.

End Quote

What we have is a long established, tried and tested natural system filtered through 100s of millions of years of evolution. The collection of plant available nutrients through this system is truly remarkable but incredibly fragile and robust at the same time. 

Robust in the sense that the mycorrhizal elements survive droughts, floods and fire to re-populate the soil spaces quickly. 

Fragile in the sense that two particular human activities destroy them. The first is our old friend tillage or, in the vernacular, digging. This action breaks the filaments destroying the interconnections. The other more subtle method of destruction is artificial fertiliser. I say subtle because of the manner in which fertilisers destroy the system. 

Let’s run a thought experiment. A group of humans have to spend all day collecting their food from the fields. Grains need to be processed, vegetables need to be cooked and meat requires slaughter, butchering and cooking. Now these humans return all the waste back through their system, maintaining fertility and exploiting photosynthesis to their heart’s content. Along comes an unseen hand during the night and huge amounts of fast food are delivered to the front door. No questions, no payments required, just free food. Not the same as they were eating but close enough and without having to do anything. What will happen?

I assume the educated and good looking listeners to this podcast would choose to avoid the fast food. The majority of people will however take the free stuff, despite any longer term consequences.

When humans drop chemical fertilisers on their soil, they are, in effect, providing the fast food from our thought experiment. The plants take up the NPK directly without the need for accessing the mycorrhizal elements. Like the fast food, the longer term effects are to create a barren soil. Barren of anything but crops, the fertiliser and, taking advantage of the free food, weeds. Other effects, over time, are also like the obesity epidemic. The crops grown may well shoot up quickly, they tend to be soft for want of a better word. Delicious to insects who can pick out a weakness with their eyes shut. Pretty much like type 2 diabetes and a diet of fast food. Ok, I’m probably taking that too far.

In effect the chemical fertilizers provide nutrients directly to the plants’ roots and the interconnection with mycorrhizal channels is not needed for the immediate, short term growth of the plant. A mechanism to accumulate suddenly available nutrients outside the mycorrhizal system kicks in. Eventually, it would appear, the constant triggering of that mechanism severs the interconnection. On top of this we added constant tillage to destroy whatever mycorrhizal material may have been in the soil and we find ourselves in the situation we have nowadays.  

This would seem to be a one way street. Once the interconnection is broken and the tillage destruction added, then we might be trapped into constant reliance upon chemical additives to make up for the loss of more natural systems. However this is not the case. As many of us discovered during the lockdowns around the world, the amount of yeast floating around in the atmosphere to kick off a sourdough starter is much more than would have imagined. I think the fact these things are invisible has an impact on our thinking. This applies to both sourdough and soil microbiota.

As was noted in the quote previously, these mycorrhizal fungi pre-date the evolution of land based plants. There is, it would appear, a huge reservoir of these available to restart the system whenever we, humans, wake up to ourselves. Given that plants colonised the land before animals we can postulate a co-evolution between the two as the animals spread out to explore and exploit available niches. What I’m getting to is this: The use of animal manures is a critical element in the kickstarting of the mycorrhizal systems. The manures provide food not just for the plants but for the fungi as well. And as noted in the quote, the fungi are far more efficient at collecting nutrients than plant roots are.

A case in point. Our place divides nicely into three half acre-ish units. The orchard, the soft fruit and some pasture all lie within the home half acre. The next half acre out from home is where I’ve been running the pigs. Rotating them across the space. They have removed any trace of blackberry, and there was some there to start with, they have manured and urinated in different places as they moved. The last half acre sits just beyond this pigged over area. Planting broad beans into both areas has been illuminating. Where the land had been pigged, the beans leaped out of the ground, are deep rich dark green in colour and are untouched by insects.

Those planted in the non-pigged half acre have struggled to grow. They are a much lighter green, have smaller stems and have struggled. These I have slashed and allowed to rot into the soil and had peas planted through them. Again, a lack of vigour. Even the buckwheat I followed the peas with in straggly and will be slashed. The one bed, 50m x 5m where I have slashed three “crops” is now showing some vigour with oats, barley and wheat in this area. Now the pigs are of a size where they need to meet their maker so they will not be working on the last half acre. Next Spring, September/October/November here in the Southern Hemisphere will see the arrival of a couple more piglets and the cycle will continue. I’m also making as much compost as I can to spread on this half acre but there are limits to the available organic matter, as ever. In the meantime I’m also knocking up a mobile duck house so they quakers can start their manuring process on this last half acre. As it turns out growing food is a constant feedback loop from idea to test to information gathered to altered plans. Or as Bear Grylls puts it so much more succinctly: Adapt, Improvise, Overcome.

This whole pig/no pig situation reminds me of John Seymour’s statement along the following lines: “The quickest way to make compost is to put it through an animal. 24 hours and you have the best plant food in the world. 

The focus will be getting manures/compost on gardens, building soil fertility and allowing the specialists, the mycorrhizal fungi to do the work for me and for free.

In the garden, no-dig becomes even more important in the knowledge that these fungi are better than either human created nutrients or the plant’s roots at collecting the nutrients and delivering them to the roots.

And the bonus is we decarbonise the air and recarbonise the soil.

Thank you all for listening and I’ll be back next week!



The ChangeUnderground Academy No-Dig Gardening Course:



email: jon@worldorganicnews.com

Transcript https://worldorganicnews.com/episode248/


How It Works



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