User:Paleorthid/Sandbox/Article Nursery/Criticism of Humus

1

~~Biogeochemical processes convert dead plant material into organic products that are able to form intimate associations with soil minerals,~~

Alt: Decomposition products of dead plant materials form intimate associations with minerals,

~~making it difficult to study the nature of soil organic matter.~~

Alt: making it difficult to isolate and characterize soil organic constituents.

~~Early research based on an extraction method assumed that a 'humification' process creates~~

Alt: Studies based on the success of alkaline extraction to remove a portion of the organic constituents in soil led to the theory that a 'humification' process created 'humic substances' in soil equivalent to those removed by alkaline extraction.

~~recalcitrant (resistant to decomposition) and large 'humic substances' to make up the majority of soil 'humus'.~~

~~However, these 'humic substances' have not been observed by modern analytical techniques.~~

Alt: However, the destructive nature of the alkaline extract significantly alters organic materials and equivalents in soil have not been observed.

~~This lack of evidence means that 'humification' is increasingly questioned,~~

ALt: Absent validation, the theory of 'humification' is unsupported by the evidence,

"yet the underlying theory persists in the contemporary literature, including current textbooks."

~~The conceptual problem with defining 'humic substances' by an extraction process is threefold:~~

alt: Three criticisms:

1) Extraction is always incomplete.

Alt: 1) Alkaline extraction leave constituents behind.

2) ...the harsh alkaline treatment ... giving the resulting 'humic' and 'fulvic' fractions ... an exaggerated chemical reactivity...

Alt: 2) Alkaline extraction alters constituents, exaggerating their performance

3) The development of this extraction preceded theory, tempting scientists to develop explanations ... rather than develop an understanding of the nature of all organic matter in soil. Over time, this attempt to mechanistically explain the formation of operationally defined 'humic substances' also led to their definition as synthesis products without the link to the alkaline extraction.

The issue of humification becomes a problem of false inference.

Lehmann, J.; Kleber, M. (2015-12-03), "The contentious nature of soil organic matter", Nature, 528 (7580): 60–68, Bibcode:2015Natur.528...60L, doi:10.1038/nature16069, PMID 26595271, S2CID 205246638

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Decomposition products of dead plant materials form intimate associations with minerals, making it difficult to isolate and characterize soil organic constituents. 18^th century soil chemistry studies based on the success of alkaline extraction to isolate a portion of the organic constituents in soil led to the theory that a 'humification' process created 'humic substances' in soil equivalent to the extraction. However, equivalent humic substances' have not been observed in soil. Although 'humification' theory is unsupported by evidence, "the underlying theory persists in the contemporary literature, including current textbooks." ^[1] Attempts to redefine humification and humus in valid terms have resulted in a proliferation of contradictory definitions, "with far-reaching implications beyond our ability to communicate scientifically accurate soil processes and properties."^[2]

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Humus, as understood previously, may not exist.^[3] Few know ^[4] that the textbook theory of soil organic matter is false.^[5] But new textbooks are picking it up.^[6] Changes are certainly coming but the question remains: What will the new soil organic matter paradigm look like?^[7] A continuum model ...^[8]

^ Lehmann, J.; Kleber, M. (2015-12-03), "The contentious nature of soil organic matter", Nature, 528 (7580): 60–68, Bibcode:2015Natur.528...60L, doi:10.1038/nature16069, PMID 26595271, S2CID 205246638, This lack of evidence means that 'humification' is increasingly questioned, yet the underlying theory persists in the contemporary literature, including current textbooks.
^ Lehmann, J.; Kleber, M. (2015-12-03), "The contentious nature of soil organic matter", Nature, 528 (7580): 60–68, Bibcode:2015Natur.528...60L, doi:10.1038/nature16069, PMID 26595271, S2CID 205246638, The issue has also been approached by redefining 'humic substances' as the portion of soil organic matter that cannot be molecularly characterized or by calling all soil organic matter 'humus'. We argue that this compromise - maintaining terminology but altering its meanings in varying ways — hampers scientific progress beyond the soil sciences.The [need for accurate models] of soil organic matter does not allow a confusing middle path; it requires leaving the traditional view behind to bring about lasting innovation and progress. This is critical as scientific fields outside the soil sciences base their research on the false premise of the existence of 'humic substances'. Thus an issue of terminology becomes a problem of false inference, with far-reaching implications beyond our ability to communicate scientifically accurate soil processes and properties.
^ Popkin, Gabriel (27 July 2021), A Soil-Science Revolution Upends Plans to Fight Climate Change, Quanta Magazine, 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.
^ Popkin, Gabriel (27 July 2021), A Soil-Science Revolution Upends Plans to Fight Climate Change, Quanta Magazine, Few outside the field of soil science have heard of humus's demise.
^ Popkin, Gabriel (27 July 2021), A Soil-Science Revolution Upends Plans to Fight Climate Change, Quanta Magazine, "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)
^ Popkin, Gabriel (27 July 2021), A Soil-Science Revolution Upends Plans to Fight Climate Change, Quanta Magazine, "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."
^ Popkin, Gabriel (27 July 2021), A Soil-Science Revolution Upends Plans to Fight Climate Change, Quanta Magazine, If the humus paradigm is coming to an end, the question becomes: What will replace it?
^ Popkin, Gabriel (27 July 2021), A Soil-Science Revolution Upends Plans to Fight Climate Change, Quanta Magazine, 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.

[1] Lehmann, J.; Kleber, M. (2015-12-03), "The contentious nature of soil organic matter", Nature, 528 (7580): 60–68, Bibcode:2015Natur.528...60L, doi:10.1038/nature16069, PMID 26595271, S2CID 205246638, This lack of evidence means that 'humification' is increasingly questioned, yet the underlying theory persists in the contemporary literature, including current textbooks.

[2] Lehmann, J.; Kleber, M. (2015-12-03), "The contentious nature of soil organic matter", Nature, 528 (7580): 60–68, Bibcode:2015Natur.528...60L, doi:10.1038/nature16069, PMID 26595271, S2CID 205246638, The issue has also been approached by redefining 'humic substances' as the portion of soil organic matter that cannot be molecularly characterized or by calling all soil organic matter 'humus'. We argue that this compromise - maintaining terminology but altering its meanings in varying ways — hampers scientific progress beyond the soil sciences.The [need for accurate models] of soil organic matter does not allow a confusing middle path; it requires leaving the traditional view behind to bring about lasting innovation and progress. This is critical as scientific fields outside the soil sciences base their research on the false premise of the existence of 'humic substances'. Thus an issue of terminology becomes a problem of false inference, with far-reaching implications beyond our ability to communicate scientifically accurate soil processes and properties.

[3] Popkin, Gabriel (27 July 2021), A Soil-Science Revolution Upends Plans to Fight Climate Change, Quanta Magazine, 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.

[4] Popkin, Gabriel (27 July 2021), A Soil-Science Revolution Upends Plans to Fight Climate Change, Quanta Magazine, Few outside the field of soil science have heard of humus's demise.

[5] Popkin, Gabriel (27 July 2021), A Soil-Science Revolution Upends Plans to Fight Climate Change, Quanta Magazine, "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)

[6] Popkin, Gabriel (27 July 2021), A Soil-Science Revolution Upends Plans to Fight Climate Change, Quanta Magazine, "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."

[7] Popkin, Gabriel (27 July 2021), A Soil-Science Revolution Upends Plans to Fight Climate Change, Quanta Magazine, If the humus paradigm is coming to an end, the question becomes: What will replace it?

[8] Popkin, Gabriel (27 July 2021), A Soil-Science Revolution Upends Plans to Fight Climate Change, Quanta Magazine, 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.

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