Soil carbon & organic matter
Where stable soil carbon actually comes from, how long it stays, and why two decades of textbook chemistry on the subject is being rewritten.
Notes
This page covers an argument that is still running, and the records on it should be read that way.
The older account held that stable soil organic matter was a class of large, chemically recalcitrant “humic” molecules. Work over the last decade has largely displaced that: persistence looks less like an intrinsic chemistry and more like a matter of physical arrangement — carbon bound to mineral surfaces, occluded inside aggregates, or simply out of reach — and much of the stable pool appears to be the necromass of microbes that ate simple compounds and died.
That is not a small correction. It changes what a management practice has to accomplish to build carbon, and it changes what a soil test is measuring. The people here are on several sides of it.