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.

2
Decomposition products of dead plant materials form intimate associations with minerals, making it difficult to isolate and characterize soil organic constituents. 18th 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." 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."

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