I usually wouldn't post this sort of thing on here but thought this was a sufficiently monumental piece of information to merit doing so...
From a post by Toby Hemenway on FedBook:
Some amazing news on the soil science front. Humus doesn't exist. Several recent articles are showing that humic and fulvic acids and many of the other humic components of soil are artifacts of the alkaline treatment that is used to measure humus content, and don't, in fact, exist in untreated soil. When OM is measured using non-destructive methods such as NMR spectroscopy, no humic compounds can be found. Organic matter does not degrade into "stable" humic components, it simply decomposes into a continuum of smaller and smaller carbon compounds. There is constant, slow turnover of carbon in soils, not a semi-permanent trapping of carbon into "humus." Humus, meaning a stable form of carbon visualized by alkaline extraction, seems not to exist. It's an artifact of the lab method. This is kind of blow-away news for those of us who teach soil science--and it's a good lesson on how the methods we use determines what we see. Teachers, start revising how you teach soils, and stop talking about humus. Most of the articles on this are behind journal paywalls, but some of the abstracts are available. One article is Lehmann, J.; Kleber, M. (2015-12-03), "The contentious nature of soil organic matter", Nature 528:60-68. There is a short video based on that article linked below. https://www.youtube.com/watch?v=-n6emCNEmKg -- *In order to change an existing paradigm you do not struggle to try and change the problematic model /* *You create a new model and make the old one obsolete /* *That, in essence, is the higher service to which we are all being called. //* Buckminster Fuller