please tell me about the soil microbes
I would be DELIGHTED to tell you about my soil microbes.
So, there are a ton of different kinds and they have all kinds of different metabolic needs. Most consume organic matter, but where we need oxygen and exhale CO2 and create water as a byproduct, that's not always the case for microbes. Some of them do that, meanwhile others need nitrate, certain manganese or iron ions, sulfate, or CO2. And instead of water as the byproduct, they produce nitrogen gas, ammonium, manganese and iron in different ionic forms, sulfur, or methane.
This big scary looking chart is essentially that. It's called the redox ladder because all those metabolic processes are oxidation-reduction reactions. And, crucially, they happen more or less in order as soil runs out of oxygen.
That's because the different types of microbes are competing with each other for space, food, etc. and one type will predominate most of the time.
Of course, well-aerated soil has a constant supply of oxygen and will never move on to those other reactions. But if soil is, say, waterlogged, it can run out of oxygen. Sure, some oxygen will diffuse through the water (that's how fish breathe), but it does so very slowly compared to the rate of diffusion in air. In waterlogged soil, there's no way it'll keep up with the consumption rate, so you wind up with an environment devoid of oxygen - anerobic is the technical term.
That means other microbes and other metabolic processes become a big deal. Including my favorite, methanogenesis! That just means methane production, and it happens, theoretically, when oxygen and all those other analogous chemicals run out, and only CO2 is left.
I spent three years trying to confirm that theory, and the data I got was supportive but incomplete. I was especially interested in soil that gets flooded, unflooded, and flooded again, going back and forth repeatedly between aerobic and anerobic.
We were hoping that someday this could be used to predict methane emissions from flooded soil (e.g. wetlands, rice paddies, riverbanks) on a large scale, but that would take years more research.
