Analysis of information sources in references of the Wikipedia article "History of soil science" in English language version.
The present paradigm views humus as a system of heteropolycondensates, largely produced by the soil microflora, in varying associations with clay (Anderson 1979). Because this conceptual model, and simulation models rooted within the concept, do not accommodate a large char component, a considerable change in conceptual understanding (a paradigm shift) appears imminent.
A new generation of soil studies powered by modern microscopes and imaging technologies has revealed that whatever humus is, it is not the long-lasting substance scientists believed it to be. Soil researchers have concluded that even the largest, most complex molecules can be quickly devoured by soil's abundant and voracious microbes. The magic molecule you can just stick in the soil and expect to stay there may not exist.
"The latest edition of The Nature and Properties of Soils, published in 2016, cites Lehmann's 2015 paper and acknowledges that "our understanding of the nature and genesis of soil humus has advanced greatly since the turn of the century, requiring that some long-accepted concepts be revised or abandoned."
If the humus paradigm is coming to an end, the question becomes: What will replace it?
Lehmann is pushing to replace the old dichotomy of stable and unstable carbon with a "soil continuum model" of carbon in progressive stages of decomposition. But this model and others like it are far from complete, and at this point, more conceptual than mathematically predictive.
Few outside the field of soil science have heard of humus's demise.
"The theory of soil organic carbon accumulation that's in that textbook has been proven mostly false ... and we're still teaching it." (Gregg Sanford)
