Monday, 16 May 2016

Humus may not exist! (#journal)

Humus doesn't exist?

According to a post by Toby Hemenway, 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. 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.

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