Talk:Humus

Untitled

Should "humic matter" be directed here? Kjkolb 09:03, July 22, 2005 (UTC)

It does now. DavidHallett 23:30, 17 February 2006 (UTC)

Humus is not just a desirable element of fertile soil. It is an indispensable link in the life cycle of all life on earth. As the "composition" phase of the life cycle concludes upon the event of excretion of waste or death the "decomposition" phase begins. This is when the complex organisms formed from the elemental substances in plant matter are broken down into their original elemental form and then moved to the soil by gravity so as to be available as nutrient for future plant growth. It is a circle with two halves -- one half in construction the other in deconstruction.

Etymology

Does anyone know where the word Humus comes from, is it related to the dip? Trcunning 08:25, 13 July 2007 (UTC)

It is Latin for soil.  --Lambiam 12:18, 18 December 2007 (UTC)

Words are travellers. The Word Humus is latin. But it has its origin in Greek. The greek word for humus in both ancient and modern Greek is "χώμα" (it sounds homa) and means top soil. It comes from the ancient greek verb "χώννυμι" which means accumulate. — Preceding unsigned comment added by 94.70.1.0 (talk) 18:56, 2 September 2011 (UTC)

Proposed merge

I propose we merge soil organic matter into humus, as they cover similar ground. This is part of a large discussion, please feel free to join in here. Anxietycello (talk) 14:44, 9 July 2008 (UTC)

Oppose From the WP:SOIL perspective, humus dominates, but is only one component of soil organic matter, the subdominant components being live roots (10%) live critters (5%), and pre-humus organic matter: recognizable dead stuff [1]. Narrower perspectives exclude the living, but none narrowly exclude decaying plant matter (pre-humus) with soil organic matter. Example: lab reported soil organic matter: the procedure is intended to quantify every molecule of non-mineral C (thus no carbonates) sent in by the soil sampler. Not all humus is a component of soil: leaf mold, compost. Humus and soil organic matter should be two separate articles.--Paleorthid (talk) 16:29, 9 July 2008 (UTC)

Oppose per Paleorthid above. Humus is a huge topic and may need splitting not merging. Plumpurple (talk) 16:33, 2 November 2008 (UTC)

Image

The image caption doesn't state the one thing it should: Which of the layers is humus. Kafziel ^{Complaint Department: Please take a number} 23:02, 31 January 2011 (UTC)

Proposal for a modification of humus definition.

The definition of humus as "any organic matter that has reached a point of stability, where it will break down no further and might, if conditions do not change, remain as it is for centuries, if not millennia" may be improved to gain clarity and precision. In Principe "any organic matter" gives little information. Then, it is not true that humus does not mineralize, because it does, at an anual rate of approximately 1,5 to 2%, depending on conditions.

This is my proposal: "Humus is the fraction of soil organic matter of chemical polymeric nature and physical colloidal properties that has been formed by the activity of soil microorganisms using vegetal decomposition matter, and minerals, and has reached a high degree of stability."Auró (talk) 16:00, 30 April 2011 (UTC)

this language is too academic... V.B. (talk) 15:46, 9 May 2012 (UTC)

The Gunning Fog Index on your proposed text is 28.5 years of education to understand the text on the first read. The Flesch Reading Ease is -1.26, which is very poor. To keep it at the 14 year level would require an index of about 40. The intro paragraph should be understandable by the vast majority and any greater exactness should be added in the text that follows. I propose the following intro para: "Humus (coined 1790–1800; < Latin: earth, ground[1]) refers to any organic matter that has reached a point of stability, where it will break down no further and might remain so for centuries, if not millennia.[2]" That requires about 18 years of education to understand on the first read where the original requires 22 years. It drops to 16 years if the parenthetical insertion is left out. Personally I feel that all these article should aim for a reading level of 12 years of education which is a Flesch Reading Ease of 30 or greater. There are obviously exceptions to that in the case of highly technical articles.Zedshort

I think your proposal is equivalent to leave it as it is.--Auró (talk) 15:04, 11 August 2012 (UTC)

What destroys stable humus?

There ought to be a section on this. I am guessing: high nitrogen fertilizers, compaction, regular plowing... (?) V.B. (talk) 15:44, 9 May 2012 (UTC)

I believe there is a type of fungus that can destroy humus. Humus itself is essentially an inert material with respect to plants and soil microbes as the usable nutrients nitrogen, sulfur, calcium, etc. have been stripped out of the original material and the end product, humus, is essential a waste product with little food value. Soil nutrient ions can attach to the humus and afford plants those nutrients but humus by itself has little food value. It acts as a means of storing nutrients as absorbed and adsorbed ions. The fungi apparently use some of the material for food and building its body. Humus is stabilized by its attachment to clay, making it further resistant to breakdown by soil bacteria. In the very wet, high temperatures of Amazonia, humus is destroyed by fungi, and clay is washed from the soil leaving no colloids to hold on to the nutrient ions unless charcoal is incorporated. Charcoal is very, very stable to decomposition. Zedshort (talk) 19:48, 9 August 2012 (UTC)

Difference with compost

What's the difference between humus and compost ? Reading both articles, this is not clear to me. There is a documentary where a Mennonite "soil fertility expert" attempts to define both, explaining that humus is compost further degraded. --Jerome Potts (talk) 23:42, 15 October 2014 (UTC)

You are right in calling attention to this subject. I think that both articles are not properly explained, in order to see the distinction, that no doubt exists. I take note to do something about it, in case nobody is willing to act more quickly than me. --Auró (talk) 21:38, 16 October 2014 (UTC)

Humus is naturally produced in the decomposition of soil organic matter. There is an article about soil organic matter, so this is the first place to act, and where I will begin.--Auró (talk) 13:46, 19 October 2014 (UTC)

Criticism

I propose a new section, Criticism...: With an explanation build around these excerpts from Lehmann, J.; Kleber, M. (2015-12-03), "The contentious nature of soil organic matter", Nature, 528, doi:10.1038/nature16069:

[biogeochemical] processes convert dead plant material into organic products that are able to form intimate associations with soil minerals, making it difficult to study the nature of soil organic matter. Early research based on an extraction method assumed that a 'humification' process creates 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. This lack of evidence means that 'humification' is increasingly questioned, 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: 1) ... extraction is always incomplete... 2) ...the harsh alkaline treatment ... giving the resulting 'humic' and 'fulvic' fractions ... an exaggerated chemical reactivity... 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.

Greater aromaticity compared to whole soil

Historic interpretation = ‘Humification’ creates polyaromatic molecules.

Evidence-based interpretation = Not all alkaline extracts are enriched in aromatics; pyrogenic carbon and microbial metabolites (not waste products) create aromatic-rich alkaline extracts

More nitrogen heterocycles compared to whole soil

Historic interpretation = Heterocyclic nitrogen is a product of proposed ‘humification’ reactions

Evidence-based interpretation = Analytical artefacts during quantification; pyrogenic nitrogen is heterocyclic and alkali extractable

Glass transition behaviour (a phase change requiring some level of molecular order)

Historic interpretation = Formation of large polymers

Evidence-based interpretation = Common for some known biomolecules and pyrogenic carbon

This criticism of humification theory affects several articles including humic acid, and humin. The criticism related to this article is that humus, as defined, does not exist in soil. -- Paleorthid (talk) 23:55, 26 February 2016 (UTC)

This article is rated as "start class", and therefore it is lacking a lot of information. To add the proposed criticism section to such an article has no much meaning, as it criticizes something that is in great part absent from the article.--Auró (talk) 23:02, 27 February 2016 (UTC)

@Auró: If that opinion is supported by others, I can certainly userfy the criticism section until the article is sufficiently improved. However, please consider that 1) humification redirects to this page, and 2) The humification section is half the article. I added the criticism section to maintain WP:NPOV which "means representing fairly, proportionately, and, as far as possible, without editorial bias, all of the significant views that have been published by reliable sources on a topic." Proportionality seems to fit with what you are asking. I will pare back the wordiness accordingly. -- Paleorthid (talk) 05:38, 28 February 2016 (UTC)

Paleorthid I agree with your argument, and accept that more opinions are needed to support or otherwise my petition. If these opinions are lacking, I leave it to your judgment. Any way, this has reminded me, and hope others, that this article needs some work for expansion.--Auró (talk) 22:07, 28 February 2016 (UTC)

I am looking for an opportunity to convert the section to a much less intrusive parenthetical mention, much the way User:Richard Keatinge accomplished with this edit at dark earth. -- Paleorthid (talk) 23:45, 28 February 2016 (UTC)

I would encourage you to go ahead and do that; the Criticism section in its current form doesn't make sense (and nor does the material you have quoted here in Talk). Is it being claimed that humus doesn't exist? Or that there is no sound evidence for its existence? If it does exist, and if it is not present in 'unprocessed' organic matter, then presumably there must be some process going on that 'humifies' unprocessed organic matter. What else could 'humification' refer to, than that process? MrDemeanour (talk) 15:45, 17 April 2017 (UTC)

There is a newer article published in Quanta, with quotes from not only Lehmann. https://www.quantamagazine.org/a-soil-science-revolution-upends-plans-to-fight-climate-change-20210727/ However I have not kept up with wikipedia's reference syntax and am not going to attempt to add this reference. It's fun reading though, and yes the Lehmann cohort are indeed saying that humus does not exist. 2001:981:8EBE:1:464:F3BC:F187:9E60 (talk) 09:19, 17 September 2021 (UTC)

External links modified

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Assessment comment

The comment(s) below were originally left at Talk:Humus/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

* Needs references, wikify and cleanup. -- Paleorthid 19:47, 2 December 2006 (UTC) Indications of high importance: {{WPCD}}, >200 backlinks

Last edited at 19:28, 31 July 2008 (UTC). Substituted at 18:28, 29 April 2016 (UTC)

mull moder mor

THESE TERms seem to be missing from wikipedia and yet they appear fundanetal for soil development understanding re humus. Also the article contains a statement saying humus is an unproven theory akin to pseudoscience. Perhaps this could be better written to explain that long processess cannot just be observed but must be evidenced?

here is a suitable short and understandable link for a source on this http://eusoils.jrc.ec.europa.eu/library/maps/Biodiversity_Atlas/download/14.pdf  — Preceding unsigned comment added by 213.162.68.29 (talk) 14:28, 26 May 2016 (UTC) 

These terms can be seen in the German wikipedia article on humus, where they are explained and also that they originate from Swedish. So I put a template translate from the German article, which also has better pictures etc. on humus. — Preceding unsigned comment added by 213.162.68.29 (talk) 14:38, 26 May 2016 (UTC)

External links modified

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Blue Carbon

I just fixed a link in the Humification/Stability subsection; the link pointed to 'Soil Carbon', not to 'Blue Carbon'. But it then becomes clear that 'blue carbon' is not a type of soil carbon at all; it is carbon fixed in oceans (I didn't think there were any kinds of carbon that were actually blue!). So I am now going to change the text to read (and link to) 'Soil Carbon'.

The passage is cited to an academic article on 'Amazonian Dark Earths', which I do not have access to; but I suspect it does not support the claim that blue carbon is involved in soil carbon (or in amazonian dark earths). Revert unhesitatingly if I am in error! MrDemeanour (talk) 10:41, 4 October 2017 (UTC)

Mycorrhizae?

The section 'Transformation of Organic Matter Into Humus' erroneously states: "The process of humification can occur naturally in soil, or in the production of compost. Organic matter is degraded into humus by a combination of mycorrhizal fungi,[11]", misquoting the source, which actually explains that mycorrhizae simply provide increased access to mineral P through the extra-radical network it provides. In fact, organic matter is degraded by saprotrophic fungi.218.185.237.154 (talk) 23:14, 4 December 2017 (UTC)

So fix it? MrDemeanour (talk) 16:37, 5 December 2017 (UTC)

Is that a question? Seems like a good idea to explain a suggested change before removing it, in case authors of the change have some thoughts. Basic decency, but whatever.218.185.237.154 (talk) 13:56, 6 December 2017 (UTC)

I don't agree; if something is plainly wrong or misleading, then I think it is best to fix it promptly. If the person who posted the incorrect material has thoughts, they can bring them to Talk if they see fit. I'm all in favour of decency, but it shouldn't result in incorrect information staying in WP a second longer than necessary.

Also, ISTM that quite a lot of people come to Talk, and comment that the article is wrong, but never try to fix it. Perhaps they think you aren't allowed to edit Wikipedia until you have somehow been 'appointed' an editor. MrDemeanour (talk) 14:49, 6 December 2017 (UTC)