Due to interrupted news reading thanks to Feedly (my news reader) bugs, today I’m thinking about compost and mulch.
What makes a good compost? What makes a good mulch? Where do we delineate the two? Today I want to start with the first question.
In my earlier post on the Carbon & Nitrogen Priming of Organic Matter I highlight the desire for organic matter with a C:N below 50:1 if we want to be priming our soils and building soil carbon. Composting is one way to do that with a general target of 30:1, but in the process of creating compost are we maximising the potential of the materials used to create it and the microbiology that comes along for the ride? Read some of my thoughts about that in Hot Compost, Cold Compost? Not Compost. [Rant]
We’ve also seen in How much Soil Organic Carbon is best? that there’s a tipping point for fungally dominated soils, and so it only makes sense to want to prioritise fungi.
I recently watched Charles Dowding turning a tonne of compost to get more air into his pile. I asked him in the comments what he’s doing differently this year and he replied that he’s trying to add more wood shreddings to increase the fungal part, and manage the moisture content with roofing. Both excellent goals.
The turning however is what got me thinking. I know from previous research on farmland that tilling soils reduces mycorrhizal fungi by half in the first month, and also that for every subsequent month left fallow those remaining fungi halve again. Is it the same for compost? How does the heat affect them and other organisms? Their spores are said to be invincible by some, but are they all?
That leads to the question of is turning compost desirable at all for fungally dominated compost? Is the heat in compost even desireable?
Most composting methods like Charles uses, turn compost, effectively tilling it. Most compost is also left fallow, without a living host for mycorrhizal fungi and their symbiotic relationship.
There are composting methods such as the Johnson Su Bioreactor and other no turn composting methods that solve the first problem, but I’m yet to see a plant that can survive the temperatures composting creates to host those mycorrhizal fungi. Perhaps at the edges they do? But for how long as the nitrogen and carbon declines as organisms take the labile carbon up?
To solve this many people later add mycorrhizal fungi inoculates, however testing has shown nearly all don’t actually contain what they’re said to when you receive them, and they likely contain all kinds of other foreign organisms.
Others collect Indigenous Micro Organisms (IMO) from local natural settings and culture those, or create teas and add them later. However I’m yet to see any that culture them in the presence of host plants. And we know from laboratory culture techniques that very few species can be cultured in artificial environments like petri dishes and various agars.
How vital then are host plants for culturing mycorrhizal fungi and other symbionts?
Is it a non-issue or something we’ve overlooked in creating symbiont dominated soil amendments?
Should the Johnson Su Bioreactor style design be planted out to look more like the drum planter with the type of plants you plan to grow?
Here’s a design I’ve just thought up. Below is the Permi Flix Bioreactor top-down view, a modification of the Johnson Su. Inoculated with multiple IMO soil sections around the perimeter, with aeration pipes in the middle. With a watering system just like the Johnson Su. The idea is that you cull and select for plants and microbes that produce the best results planted in the different IMOs around the outside edge, as highlighted by the coloured sections. I’m calling it the game of life. It could also be done with multiple composters and the same material, each with their own IMO mix.
Wait a week before planting?
Or just mulch, inoculate, plant and never disturb?
Just a thought on a Feedly-deprived day.