Eric and list:
Thanks for this CDR-type lead.
Your link (a PR piece from Washington State University) gives this added
information:
Marc G. Kramer, Kate Lajtha, Anthony Audfenkampe. Depth trends of soil organic
matter C:N and 15N natural abundance controlled by association with
Summary is here (and includes links to abstracts):
https://www.sciencedaily.com/releases/2017/11/171108092406.htm
The gist: We probably have underestimated how much carbon can be stored in
agricultural soil minerals (found in the first 3 feet or so) and changes in
agricultural practices can
