Humification Theory [Rant]

“Soil organic matter (SOM) derives from dead plant parts in the litter layer”
“A fraction of SOM persists because it can resist decomposition.”
“The process which converts litter into resistant or “recalcitrant” soil organic matter
was called humification”
The product of humification = presumably ‘stable’ organic matter = is called humus

I don’t believe in humification theory. There, I’ve said it. I cringe every time I hear the word humus.

Biochar isn’t even that stable in soil. Unless it’s buried where oxygen doesn’t reach it deep deep in the profile. Something fungi can do with it by embedding it inside soil microaggregates where it won’t be oxidized or access by other organisms. But carbon cycling in soils doesn’t stop there.

I’m not the only one that questions it. Here is a video summary of a paper by Johannes Lehmann and Markus Kleber from 2015, and there are others I’m too lazy to link to.


How is carbon stored in the soil?
Thomas Fester

Here are some slides from a talk about the paper, a talk I wish I could find, and the scientific paper from Nature.
However even Johannes Lehmann the co-author of the paper uses the word humus in the following talk on soil carbon two years ago around the time the paper was released. It’s so engrained in people and our language that I believe it will be around long after the “stable” humus is.

 

No doubt I’m bound to use the word humus to confuse myself and others too, just a heads up then… 🙂

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