Thread: Hot/thermal composting revised and microbial life

Hi all,
I have in the past posted on hot composting where I have used just lawn clippings in the pile, the pile gets hot, I water it when I turn it, then in time it cools down, I then apply it as a surface mulch, I have been doing this here for the last ten years or so and have seen improvements in the soil..... all good or so I thought.

Over this time I have had good results and some dismal results with what I can and can't grow, two things I have never been able to grow is spuds or strawberries, tomatoes, corn and asparagus have had good success with. This year toms was largely a blowout, roots badly affected by root feeding nematodes, never used to be a problem (that I saw) but this is a problem that seems to be getting worse.

So, this Why I can and Why I can't? takes me off to the library for reading mat'l on gardening/composting etc. after some rather uninspiring books I found Teaming with Microbes, now this is interesting, this book looks at the soil biology (soil food web) and the association they have with plants which is many and varied, it is well worth reading.
There is a close association that the bacteria have with the plant root within the rhizosphere, this is the area surrounding the root which extends out as far as the root hairs, (which to my eye aint very far) the bacteria provide protection from things like root feeding nematodes and also become food for bacteria feeders (vorticella) the bacteria feeders become food for the next thing and so and so on, all this eat or be eaten then provides nutrient for the plant, the plant puts out exudates (sugars) that attract bacteria to the rhizosphere and the plant will manipulate this exudate depending on what the plant wants/needs which then determines which type/s of bacteria are attracted to the rhizosphere.

There is also fungi involved, some fungi will form a mychorrizal association with the root and increase the plants ability to uptake nutrients, in return the fungi gets sugars from the plant. Some fungi will set traps to capture root feeding nematodes, I would think I don't have enough/any of these types of fungi, there is of course both desirable and undesireable bacteria/fungi but as always there is a balance so when we come along and dig/spray with a pesticide/herbacide/fungacide/anything acide we can very easily upset this balance.

Some of these discoveries are only fairly recent and ongoing, anybody interested can google people like Elaine Ingham, Jill Clapperton, (scientists) Gabe Brown (US farmer) Paul Taylor (AUS farmer) many hours of utube vids etc.

How does all this relate to composting? As I said I have been making my compost from grass clippings which is primarily bacteria food, (they decompose the easy stuff) in doing so they produce alkaline substances, this is why I see my compost at 9 or more (when freshly made, over time it will come down) and possibly why I am seeing my soil move towards alkaline and why I can't grow strawbs or spuds. What to do? As Elaine says I need to get more woody material into my pile which is fungi food, fungi produce acids which then balance the alkaline from the bacteria, so as I'm reading and looking at all this stuff the tree trimmers are about the neighborhood doing under the power lines, I end up with 2 truck loads of tree trimmings, good thing about this stuff is there's lots of leaves and the chips are from small branches/bark and growing wood and clean, good good. Better still is this is cut green so the leaves have all the minerals in them, brown leaves that fall off (deciduous) have had minerals withdrawn from them and stored in the roots waiting for the next year.
So now I add a lot more woody/leafy stuff to the pile and I now also monitor the pile temp with a compost thermometer, I also see more hyphae amongst the piles and in the mulch, good good.

Elaine promotes the use of looking at soil/compost tea brews under a microscope to see what you have/haven't got in the way of soil life, so a few phone calls and samples in hand sees me off to our local uni, I took samples from best to worst soils around the yard and some compost teas, the worst showed bacteria and sand not much else, the best showed the same but also a little more variety, things like good guy nematodes or bacteria feeders, some fungi and broken down organic matter, generally not too bad but not good either, the lecturer helping me said she will see farmers samples that have no life in them at all, typically from use of glyphosate and tillage, there were a few variations like under the fresh compost pile(3 days old) (that had just been turned) the microscope field was chockas full of bacteria, millions of, could even be billions? this would add up as this is what the bacteria do in a fresh compost pile, food+moisture+air=multiply, as Elaine says you do need to keep an eye on growth via temperature and this pile was right on the upper limit of 70°C for the first 3 days.

Elaine talks about succession, the evolution of land that has been heavily disturbed (like a volcanic eruption) to an old growth forest, with my high bacteria numbers and not much fungi suggests early succession and pioneer species, typically plants that are tough, have a long tap root and can survive on the smell of water, things we might call weeds, to hurry the succession I will be encouraging the fungi, I can really give this a boost with commercially available fungi such as the mycorrhizal forming species, will be interesting to see what happens.



Pete