Talk:Soil

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Good article[edit]

I've passed the Good Article nom for this article; it is extensive, in-depth and well sourced. Further improvements should include merging some of the one sentence paragraphs, but this article has a lot of potential. Laïka 00:15, 10 February 2007 (UTC)

Too human-centric[edit]

I see that tons of work has gone into this article and I am not any kind of expert on soil. However, one thing does bother me about the article. Most of it focuses on us humans: How we study soil, how we name it and classify it, how we use it and abuse it, and so forth. Soil has been around a lot longer than we have and will, hopefully, still be here after we are gone. I would like to see a little more about how soil is important to the whole natural world, not just to us humans. Steve Dufour 13:51, 26 February 2007 (UTC)

Sorta related. In the sub article about the creation of soil it mentions it is "anthropogenic". Is this to say that 'humans' made soil? Surely we couldnt have evolved without soil already being there, to support plant life. So how does that work?Crakker (talk) 00:13, 27 April 2008 (UTC)

The science of how soils are created is incredibly complicated so I think that it is sufficient to say "physical, chemical, biological, and anthropogenic" to keep it open to the general public. Crakker, it relates to the fact that humans can change soil to a degree that it is unrecognisable to its original form. There is talk in geological circles to call the last ten thousand years the anthropocene, as there is a distinct geological boundary between pre and post humans. Sippawitz (talk) 23:36, 21 May 2008 (UTC)

Not broad enough[edit]

I hope that the soil scientists who have been the primary authors of this article will accept that their are broader descriptions of the term in common usage: even in common professional usage. A better introductory description would be broader to cover all common usage. From there, sections and subsections could describe in more depth the wide array of detail and considerations as done here.

I think soil scientists would certainly recoil in horror if this topic had been written and recieved GA status as completely written by a crew of geotechnical engineers, geologists, geomorphologist, or glacialogists, let alone drillers, for whom the term "overburden" would suffice.... Drillerguy 17:41, 12 May 2007 (UTC)

Civil engineering project[edit]

If, in the future, someone tries to get this article up to FA status again, I think that I, and probably other people at WP:CE, would be willing to help broaden the scope of this article to include knowledge from the fields of geotechnical engineering and soil mechanics. -- Basar (talk · contribs) 01:04, 26 August 2007 (UTC)

Additionally, some people from WP:GEOLOGY may be interested in expanding the formation of soil information, and WP:BIOL participants and sub-participants might be interesting in writing about the non-human uses of soil as asked for above. -- Basar (talk · contribs) 20:51, 27 August 2007 (UTC)

De-list GA[edit]

I normally do not like to add negativity to Wikipedia, but I feel that this article should be delisted from the GA list due to its issue of not being broad in coverage per the posts above; this is criterion 3 of the GA criteria. Consequently, it may also not pass criterion 4 because of its bias towards soil science. – Basar (talk · contribs) 05:34, 13 September 2007 (UTC)

P.S. The article's original main editor is no longer on Wikipedia to correct these issues. – Basar (talk · contribs) 05:35, 13 September 2007 (UTC)
First, this should be addressed to the Wikiproject:Soil referenced above. Secondly, I agree with you Basar that this article is incomplete addressing the general topic and needs lots of work. However, rather than going backward, I would like your opinion on the following proposal: Drillerguy 12:57, 13 September 2007 (UTC)

Redirect "Soil" to disamb page and rename this one "Pedosphere" or Soil (Soil Science)[edit]

I think the topic "soil" is itself extremely broad and a comprehensive article is going to take a long time to achieve. I'm more inclined to cut the original authors slack and just help to add what I can. Either that, or different aspects could be broken out. The term "Soil" is such a broad topic that it may be akin to electricity or computer software or (a better example as an article) welding. Better than that, this topic probably needs to direct to its own disambiguation page and proceed along the path taken by water. This particular article could then address the topic from the standpoint of pedosphere or even be NAMED "pedosphere" to replace what is there as that article is basically a stub. Renamed, with the inclusion of additional aspects of biology, ecology and geology (and more references), and having the parts relating to other aspects of soil removed I think this article would actually be FA status. Granted, that is still a lot of work, but more likely achievable. I think a completely comprehensive "Soil" article would be a herculean effort. Drillerguy 12:34, 13 September 2007 (UTC)

Well, my thoughts are that we should retain a single article on soil, but that we should expand it to incorporate more aspects of soil. My reason for this view is that there is only one thing called "soil", and I think we should be able to write a single article on it, even if it is difficult. This is also the way all of the similar articles I know are arranged. The article water, which you mentioned, is probably even more difficult than soil, but it has a single article that covers many, very diverse aspects of the subject. This is also the way things have been done in the other articles you have mentioned too; these articles just have sub-articles to discuss particular aspects of the subject just like we have soil mechanics and soil compaction to discuss particular aspects of soil. I do not know what to do with the article pedosphere because I am not very familiar with the term, but from what I see in the article, it seems like we can just redirect it here because it seems more than less synonymous with soil. – Basar (talk · contribs) 05:26, 17 September 2007 (UTC)
There are actually various definitions for the term "soil". Soil has a different meaning for Soil Science, Civil Engineering and Geology. Consequently, there should be separate articles, linked from soil (or a section within the article) which would deal with the implications of these meanings of soil, e.g. Soil(engineering). I will now quote from the book by Tschebotarioff [1] "In agricultural soil science the term soil is applied only to the thin upper part of the mantle-rock penetrated by the roots of plants, which supplies them with the water and other substances necessary of their existence." For civil engineering "..This term includes all the loose or moderately cohesive deposits, such as gravel, sands, silts, , or clays, or any other mixtures".
And from Holtz and Kovacs's book: [2] "Soil, in an engineering sense, is the relatively loose agglomerate of mineral and organic materials and sediments found above the bedrock...". "Soils to a geologist are just decomposed and disintegrated rocks generally found in the very thin upper part of the crust and capable of supporting plant life. Similarly, pedology (soil science) and agronomy are concerned with only the very uppermost layers of soil, that is, those materials relating to agriculture and forestry". - Sanpaz 03:12, 18 September 2007 (UTC)
Those quotes are interesting, but I think we should still have a single page that describes these different definitions and perspectives. My reasoning is that it is not Wikipedia's style to fork a topic into several pages to present the varying definitions and points of view on a subject. Rather, it is recommended that we integrate and explain these differences. The guideline page describing Wikipedia's preferences is at WP:CFORK. I think this would be a light example of a fork, not the more serious type dealing with positive and negative aspects of subjects. – Basar (talk · contribs) 06:06, 18 September 2007 (UTC)
I understand your point Basar. I do not see this as forking content. We are not dealing here with opinion but rather with scope. The current article deals strictly with soil as dealt by Pedology. Therefore, it should be rename as Soil(science). There should be another article Soil(engineering); and if necessary a Soil(geology). But all of these three articles should be linked from one single article called 'Soil', which would explain or state the differences in scope of these definitions. I am new to this article, and I can see that it is a difficult topic to handle. What do you guys think? Sanpaz 14:54, 18 September 2007 (UTC)
There are certainly some aspects of 'soils' that are general to all three definitions. Those are perhaps the things that should be included in the unique soil article. Sanpaz 17:47, 18 September 2007 (UTC)
The different definitions/approaches to "soil" is part of the interesting aspect of the topic, that is why I would prefer the approach described by Sanpaz: a new, broad article referencing other articles which can go in greater depth without causing confusion to the general reader. Basar it sounds like that is what you favor too? Drillerguy 17:27, 24 September 2007 (UTC)
Like Basar, I feel that we should retain a single article on soil, and broaden its base. Take the content headed "soil classification" for example. This soil article content is strictly pedology oriented, but the main article (soil classification) is not. Bringing in the engineering content (and toning down the pedological perspective) could be fairly straight forward. I see too much overlap in public perception of the disciplines to reliably distinguish Soil(science) from Soil(engineering) from Soil(geology). There are articles where it is informative to sharpen those distinctions, but I don't think this (soil) is it. Paleorthid (talk) 06:53, 19 November 2007 (UTC)
Revised: better to move the classification content to soil science, at least for now. -- Paleorthid (talk) 19:05, 27 November 2007 (UTC)


I have a lecturer who is a geophysicist who states that soil is everything between the bedrock and the air. It is sufficiently broad that it captures all disciplines without being too focussed on just one. Sippawitz (talk) 23:23, 21 May 2008 (UTC)

It doesn't capture anything but minute details of soil science. This is the wiki article titled "soil" and there isn't even a link to the "soil mechanics" article. I wasn't expecting a broad topic like this to have such a poor article. The main article of "soil" should summarize ALL different aspects and sciences with "Main article:" links, instead of being an unavoidably incomplete draft of a textbook on soil science. Then this would be sum of a few of those main articles branching from the "soil" article. See the article "Water" for how it should be. Nkt777 (talk) 23:48, 23 April 2014 (UTC)
You should have seen it before. It was truly terrible and much shorter. Abductive (reasoning) 00:18, 24 April 2014 (UTC)
@Nkt777: Wikipedia is the encyclopedia that anyone can edit, so the responsibility for improving an article rests equally with everyone - including people who complain how poor it is. PaleCloudedWhite (talk) 00:28, 24 April 2014 (UTC)
So you agree it is bad? Abductive (reasoning) 00:52, 24 April 2014 (UTC)
I couldn't actually say - this is an article I put on my watchlist because I'm a gardener and geographer, but haven't edited it because my knowledge is limited. However I have little time for complaints about articles, especially from people who give the impression of knowing about the subject. I see weak articles frequently, and my response—if I have time and I'm not daunted by the subject matter—is to try and improve them, even if just a little. PaleCloudedWhite (talk) 01:06, 24 April 2014 (UTC)

Working to GA status[edit]

I am considering how I can improve this article in response to the concerns that Basar gave when it was delisted. I have summarized those, and other concerns, on the article comment page. I have copied the article to my sandbox and have started in on deconstructing the beast. I plan on using a heavy hand on the soil science, pedology (soil study), and pedosphere-driven portions. The techno-jargon index is going to drop. Cultural impacts and soil characteristics are going to get refined down to fewer words. -- Paleorthid (talk) 20:51, 25 November 2007 (UTC)

  • Replaced soil definition with: "a naturally occurring, unconsolidated or loose material on the surface of the earth, capable of supporting life." Variations of this definition are showing up in K-12 soil lessons. It is, admittedly, a soil science centric definition (with a nod to biologists and ecologists per the cited reference). However, the soil-science-perspective on soil seems to be particularly popular with elementary school educators, and this general acceptance satisfies WP:NPOV. -- Paleorthid (talk) 06:59, 27 November 2007 (UTC)
    I think it is a good definition of soil under the scope of soil science. However, as I stated in the discussion above (dated September 18), "Soil has a different meaning for Soil Science, Civil Engineering and Geology". In other words, the term 'soil' has a different scope for each discipline. I still feel that it is necessary to make clear that there are these different scopes. Sanpaz (talk) 16:22, 27 November 2007 (UTC)
    I posted it not because it was a good definition of soil under the scope of soil science, but because it was in general use. If, and when, there is a definition that better captures general acceptance, it should replace this one. Agree that it is desirable to have some article content on the different scopes, as long as it doesn't go into mind numbing differences, which is what we have within the soil science profession. pedology favors "subject to weathering" or the self-referential "to soil formation" The taxonomist subset of pedology (eg NRCS) like to insert terms like "natural bodies", ag soils folks favor "growing plants" with no mention of wee beasties, which is huge to soil ecologists and soil biologists. A small minority of soil scientists favor an emphasis on energy flux over weathering and life. They are among the few that accept lunar soil as soil, and tend to be involved with lunar and martian surface characterization. I assume some CEs and geologists also accept lunar and martian soil as soil, but haven't seen anything in the news about that. Most soil scientists do not accept the term: it's regolith to most of us. Newscasters do, so I expect that makes the lunar soil term valid from the "general acceptance" requirement of WP:NPOV. Sorry for the ramble: its a favorite subject. -- Paleorthid (talk) 19:01, 27 November 2007 (UTC)
  • Moved soil science text out of the article per my NPOV concerns & concerns with scope by other editors. (100% completed):
  1. Intro paragraph on soil science research. -- Paleorthid (talk) 21:54, 29 November 2007 (UTC)
  2. Classification section. -- Paleorthid (talk) 01:21, 30 November 2007 (UTC)
  3. Paragraph on mapping. -- Paleorthid (talk) 01:35, 30 November 2007 (UTC)
  4. Content on classification in the In nature section -- Paleorthid (talk) 01:45, 30 November 2007 (UTC)
  5. Data section. Land degradation section. -- Paleorthid (talk) 02:06, 30 November 2007 (UTC)
  6. Fields of study section. History section. -- Paleorthid (talk) 02:15, 30 November 2007 (UTC)
  • Reorganized and rewrote for readability (Complete as of January 1, 2008):
  1. Soil formation section. (encouraged WP:GEOLOGY to edit mercilessly). -- Paleorthid (talk) 01:06, 30 November 2007 (UTC)
  2. Rewrote introduction for readability, simplified. added refs. -- Paleorthid (talk) 01:30, 30 November 2007 (UTC)
  3. Characteristics section summarized. -- Paleorthid 21:22, 2 December 2007 (UTC)
  4. Uses section distilled down to bare essentials. Added {{expand-section}} with request for examples of use. With multiple editor input the resulting content should be better balanced. -- Paleorthid (talk) 05:45, 2 January 2008 (UTC)

chemical composition[edit]

This article needs to have info about the chemical composition of soil. —Preceding unsigned comment added by 76.85.197.39 (talk) 09:46, 22 August 2008 (UTC)

Ambiguity in units[edit]

In the first paragraph of the article, this sentence appears: "Most soils have a density between 1 and 2, and weigh between 60 and 120 pounds per cubic foot." After "between 1 and 2," a unit should be specified, or else the sentence triggers immediate confusion.

24.241.226.198 (talk) 10:06, 4 February 2009 (UTC)

Density is a dimensionless quantity, so just a number on its own is correct. However, the use of pounds per cubic foot is against style guidelines, so needs converting into SI units. Jonobennett (talk) 15:20, 4 February 2009 (UTC)
You are contradicting yourself! If density is a dimensionless quantity then it cannot be converted into SI units. The SI units of density are kilograms per cubic meter (kg/m³). The original complaint is valid, namely that without units specified nobody knows what the 1 and the 2 refer to.

History of soil[edit]

Was there a time where there was no soil? After the Magma of the earth had cooled and become solid rock, and life began to evolve, the layers of eroding rock chemically/physically changed and decomposing organic matter formed it? The first organisms on land were bacteria then mosses right? The snare (talk) 02:06, 28 February 2009 (UTC)

It depends on how you want to define soil, for some soil is a product of the interactions of living organisms on regolith and other parent materials, so any material that does not have an organic component to it is not soil. Others are able to talk about soils on other planets and the moon, so in that sense the Earths first soils would have been the the result of chemical and physical weathering. The first life forms on land would have been bacteria and bacteria-like algea. Mosses did not come along untill much later. Hardyplants (talk)

Possibly incorrect statement - soil fertility[edit]

In the Organic matter section it is stated that "Soils that are all organic matter, such as peat (histosols), are infertile." This seems odd to me as I would expect that soils with higher organic content would be more fertile than those with a low organic content. Indeed, the definition of organic and fertile would, to my mind, demand that fertility would correlate positively with organic content. The quote has a reference number referring to 'Foth, Henry D. (1984), Fundamentals of soil science, New York: Wiley, pp. 151, ISBN 0471889261' so perhaps somebody with access to this book, or somebody who knows more about soil and peat than I do, can consider this infertility statement and correct it if necessary. Perhaps the statement is an over-simplification? Or does it need clarifying to refer to acidity or water content rather than just to organic matter? —Preceding unsigned comment added by 213.162.104.24 (talk) 09:31, 8 July 2009 (UTC)

Soil a renewable resource?[edit]

From what I have heard about soils, earthworms, microbial decomposition, plant/animal growth and death are largely responsible for soils' formation, along with break-down of parent materials. These processes can take tens of thousands of years according to NASA (http://soil.gsfc.nasa.gov/soilform/parmat.htm), this can take hundreds or thousands of years. Topsoils have been eroding at an alarming rate (e.g. dust bowl) so while technically soils are a renewable resource, they are only renewable on a time scale akin to the renewability of petroleum.Apothecia (talk) 02:42, 2 February 2010 (UTC)

As with all categorical information, some items don't fit as well as others. Yeah, at geological scales, the soil is renewable. But then geological scales don't put food on the table. After doing an internet search, there appears to be enough debate on the issue of renewability, that the issue has no place in the lead where space does not allow proper qualification. Even if soil is technically considered as renewable, it is probably not wise to consider it as such; perhaps sustainable would be a better term. I concur eliminating the referral to renewability in the lead sentence, and then opening a discussion of the issue within the body of the article--perhaps under the "Degradation" section where it can be adequately discussed and qualified. Pinethicket (talk) 13:49, 2 February 2010 (UTC)

i believe that soil is a big part of the environment —Preceding unsigned comment added by 66.74.86.58 (talk) 01:12, 5 February 2011 (UTC)

Soil Types Diagram Incorrect[edit]

Soil types by clay, silt and sand composition.
USDA and UK-ADAS textural triangle.jpg

SoilComposition.png is drawn incorrectly. I am comparing it to a similar diagram in [3]. The tick marks on the "percent clay" side of the triangle should be horizonal, the tick marks on the "percent sand" side should point upward to the left and the tick marks on the "percent silt" side should point downward to the left. This is obvious if you pick the point in the upper right part of the brown "medium loam" region the percentages should be 23% sand, 50% silt and 27% clay. The total is 100%. But the .png would read 50% sand, 73% silt, 80% clay which is 203% and is obviously wrong. --Zedshort (talk) 05:52, 22 October 2011 (UTC)

I added a reflist, but that brought up 7 other inline cites that are scattered through this page, so I've removed it again - why don't people just use a simple url link? Anyway to answer your point, there should either be no ticks or a tick parallel to the nearest side (moving anticlockwise) at each 10% point, probably best with no ticks and a set of 10% lines within the diagram as shown here. Mikenorton (talk) 08:05, 22 October 2011 (UTC)
I shouldn't start answering things till I'm fully awake. I agree with your point, I only just noticed the arrow directions on the diagram that I linked to, so I've update my reply. I also notice that the boundaries are a little different, particularly for the 'sandy clay' field. I'll try to find a definitive diagram (if there is one) and I may be inspired to create a replacement. Mikenorton (talk) 08:18, 22 October 2011 (UTC)
So, there is an official USDA diagram, and an official UK ASDA diagram, both of which are captured (although I think rather confusingly) in this diagram (bottom right). A quick look around suggests that most countries have their own classification and related ternary diagram. Probably better to stick with the USDA one, it seems to be the most widely used. There are some diagrams out there that have different boundaries for some fields such as 'sand' and 'loamy sand' compared to the USDA standard, but none of them match the ones in this article for sandy clay. I'll create a new diagram based on the USDA one, but using the colour scheme in the existing diagram. Mikenorton (talk) 10:03, 22 October 2011 (UTC)
New diagram added to the article, replacing the incorrect one. Mikenorton (talk) 16:09, 22 October 2011 (UTC)
It is very confusing for someone not familiar with this type of diagram to figure out which lines to follow. Properly oriented tick marks as described by Zedshort would help clarify it. — Preceding unsigned comment added by BillHart93 (talkcontribs) 12:15, 2 April 2012 (UTC)
There are correctly oriented tick marks on the new diagram, although you may need to click on the diagram to see them. However, the labels are oriented in the same way for greater clarity. Mikenorton (talk) 16:23, 19 April 2012 (UTC)

Addition to Characteristics[edit]

I think the following would make a proper introduction:

The mineral components of soil may consist of a mixture of clay, sand, and silt. Even pure sand, silt or clay may be considered a soil but from the perspective of food production a loam soil with a small amount of organic material is considered ideal. On a volume basis a good quality soil is one that is 45% minerals, 25% water, 25% air, and 5% organic material, both live and dead. The mineral and organic components are considered a constant with the percentages of water and air the only variable parameters where the increase in one is balanced by the reduction in the other. The mineral constituents of a loam soil might be 40% sand, 40% silt and the balance 20% clay. Zedshort (talk) 05:08, 25 October 2011 (UTC)

Is "good quality" the best way to describe that mixture of soil? Differnt kinds of soil are of good quality for different things. For example, an oxisol would be of good quality for growing rubber or cocoa, but awful for corn (without the industrialized suplementation). An oxisol would also be an idea habitat for termites and therefore pangolin, but would not support the kind of ecosystem found in a boreal forest.

In addition I think we could have a bit on the history of the study of soils. Zedshort (talk) 05:08, 25 October 2011 (UTC)

History of Study of Soil[edit]

I propose the following to be the first article after the introduction:


The history of the study of soil is intimately tied to our urgent need to provide food for ourselves and forage for our animals.

Columella’s Husbandry, circa 60 A.D. was used by 15 generations (450 years) of those encompassed by the Roman Empire until its collapse. From the fall of Rome to the French Revolution, knowledge of soil and agriculture was passed on from parent to child and as a result, crop yields were low. During the Dark Ages for Europe, Ibn-al-Awan’s handbook guided the people of North Africa, Spain and the Middle East with its emphasis on irrigation, a translation of which was finally carried to the Southwest of the United States. After the hyper-irrationality of the Thirty Years War (mid 17th century) the stability of nations allowed intellectual activity to flourish and led in turn to the rationalization of all things, including an attempt with soil.

Jethro Tull, an English gentleman, introduced in 1701 an improved grain drill that systemized the planting of seed and of a weed hoe, the two of which allowed fields, once choked with weeds to be brought back to production and seed to be used more economically. Tull however introduced the mistaken idea that manure introduced weed seeds, and that fields should be plowed in order to pulverize the soil and so release the locked up nutrients. His ideas were taken up and carried to their extremes in the 20th century, where farmers repeatedly plowed fields far beyond what was necessary to control weeds, resulting in the dust bowl of the panhandle areas of Texas and Oklahoma of the United States.

The two course system of a year of wheat followed by a year of fallow was replaced in the 18th century by the Norfolk four-course system wherein wheat was grown in the first year, turnips the second, followed by barley, with clover and ryegrass together, in the third. The taller barley was harvested in the third year while the clover and ryegrass were grazed or cut for feed in the fourth. The turnips fed cattle and sheep in the winter. The fodder crops produced large supplies of animal manure which returned nutrients to the soil.

Experiments into what made plants grow first lead to the idea that the ash left behind when plant matter was burnt was the essential element, overlooked the role of nitrogen which is not left on the ground after combustion. Jan Baptista van Helmont thought he had proved water to be the essential element from his famous experiment with a willow tree grown in a carefully controlled conditions in which only water was added and after five years of growth was removed and weighed, roots and all and found to weigh 165 pounds The oven dried soil, originally 200 pounds was again dried and weighed and found to have lost only two ounces which van Helmont reasonably explained as experimental error and assumed that the soil had in fact lost nothing. As rain water was the only thing added by the experimenter he concluded that water was the essential element in plant life. In fact the two ounces lost from the soil were the minerals taken up by the willow tree during its growth.

John Woodward experimented with various types of water ranging from clean to muddy and found muddy water the best and so he concluded earthy matter was the essential element. Others concluded it was humus in the soil that passed some essence to the growing plant.

The French chemist Antonine Lavoisier showed that plants and animals must “combust” oxygen internally to live and was able to deduce that most of the 165 pound weight of Van Helmont’s willow tree derived from air. The chemical basis of nutrients delivered to the soil in manure was emphasized and in mid 19th century chemical fertilizers were used but the dynamic interaction of soil and its life forms awaited discovery.

It was know that nitrogen was essential for growth and in 1880 the presence of Rhizobium bacteria in the roots of legumes explained the increase of nitrogen in soils so cultivated. The importance life forms in soil were finally recognized.

Crop rotation, mechanization, chemical and natural fertilizers lead to a doubling of wheat yields in western Europe between 1800 to 1900.[4] Zedshort (talk) 04:26, 31 October 2011 (UTC)

absolutely! This will be a great addition to the page! Is there anyway you can find more than one reference though? That would help a lot with credability. Other then that great job.Millertime246 (talk) 17:01, 2 November 2011 (UTC)

Organic matter[edit]

The section on organic matter has become cluttered by the discussion of the effect of adding clay to soils in organic poor soils in Thailand. The material is interesting but probably should be moved to a new section on "Reclamation of Soils"

I removed material about Terra Preta that was in the section about humus. Humus is a very specific thing. It is a gelatinous, amorphous mix of very stable organic compounds that are the final stage of organic material decomposition and is not charcoal. We might include material about Terra Preta in the suggested section of "Reclamation of Soils." — Preceding unsigned comment added by Zedshort (talkcontribs) 03:54, 12 January 2012 (UTC)

Water[edit]

This article needs a section on water. I have been preparing to write it but hope someone else might get it started.Zedshort (talk) 22:19, 1 April 2012 (UTC)


I intend to add the following new section:

Soil Moisture

Water is essential to plants for four reasons:

It constitutes 85%-95% of the plants protoplasm. It is essential for photosynthesis. It is the solvent in which nutrients are carried into and throughout the plant. It provides the turgidity by which the plant keeps itself in proper position.

In addition, water alters the soil profile by dissolving and redepositing minerals, often at lower levels, and possibly leaving the soil sterile in the case of extreme rainfall and drainage.

In a loam soil, solids constitute half the volume, air one-quarter of the volume, and water one-quarter of the volume of which only half of that water will be available to most plants. When a field is flooded, the air space is displaced by water. The field will drain under the force of gravity until it reaches what is called field capacity. The total amount of water held when field capacity is reached is a function of the specific surface area of the soil particles. As a result clay and high organic soils have a higher field capacities. The total force required to pull, or push water out of soil is given the term suction. Alternatively, tension or moisture potential may be used.

The forces with which water is held in soils determines its availability to plants. Forces of adhesion hold water strongly to mineral and humus surfaces and less strongly to itself by cohesive forces. A plant's root may penetrate a very small volume of water that is adhering to soil and be able initially to draw water in that is only lightly held by the cohesive forces . But as the droplet is drawn down, the forces of adhesion of the water for the soil particles make reducing the volume of water increasingly difficult until the plant cannot produce sufficient suction to use the remaining water. The remaining water is considered unavailable. The amount of available water depends upon the soil texture and humus amounts and the type of plant. Cacti can for example, produce greater suction than can agricultural crop plants.

The following description applies to a loam soil and agricultural crops. When a field is flooded it is called “saturated” and all available air space is occupied by water. The suction required to draw water into a plant root is zero. As the field drains under the influence of gravity (drained water is called “gravitational water” or “drain-able water”), the suction required to be produced by the plant increases to 1/3 bar. At that point, the soil is said to have reached “field capacity”, and plants that use the water that must produce increasingly higher suction, finally up to 15 bar. At 15 bar suction the soil water amount is called “wilting percent” as the plant cannot sustain its water needs and as water is lost from the plant by transpiration, its turgidity is lost and it wilts. The next level, called “air-dry”, occurs at 1000 bar suction. Finally the oven dry condition is reached and at 10,000 bar suction. All water below wilting percentage is called unavailable water.

The amount of water remaining in a soil drained to field capacity and the amount that is available is a function of the soil type. Sandy soil will retain very little water while clay will hold the maximum amount. The time required to drain a field from flooded condition for a clay loam that begins at 43% water by weight to a field capacity of 21.5% is six days whereas for a sand loam that is flooded to its maximum of 22% water, it will take two days to reach field capacity of 11.3% water. The available water for the clay loam might be 11.3% whereas for the sand loam it might be only 7.9% by weight.


Table: Wilting point, field capacity, and available water capacity of various soil textures

Soil Texture Wilting point Field capacity Available water Capacity

Water Water Water per foot per foot per foot of soil depth of soil depth of soil depth (%) (in.) (%) (in.) (%) (in)


Medium sand 1.7 0.3 6.8 1.2 5.1 0.9 Fine sand 2.3 0.4 8.5 1.5 6.2 1.1 Sandy loam 3.4 0.6 11.3 2.0 7.9 1.4 Fine sandy loam 4.5 0.8 14.7 2.6 10.2 1.8 Loam 6.8 1.2 18.1 3.2 11.3 2.0 Silt loam 7.9 1.4 19.8 3.5 11.9 2.1 Clay loam 10.2 1.8 21.5 3.8 11.3 2.0 Clay 14.7 2.6 22.6 4.0 7.9 1.4


The above are average values for the soil textures as the percentage of sand, silt, and clay vary within the listed soil textures.


Water moves through soil due to the force of gravity, osmosis and capillarity. At zero bar suction to one-third bar suction, water moves through soil due to gravity and is called saturated flow. At higher suction, water movement is called unsaturated flow.

Water infiltration into soil is controlled by six factors:

1. Soil texture 2. Soil structure. Fine-textured soil with granular structure are most favorable. 3. The amount of organic matter. Coarse matter is best and if on the surface helps prevent the destruction of soil structure and the creation of crusts. 4. Depth of soil to impervious layers such as hardpans or bedrock. 5. The amount of water already in the soil. 6. Soil temperature. Warm soils take in water faster while frozen soils may not be able to absorb depending on the type of freezing.

Water infiltration rates range from 0.25 cm per hour for high clay soils to 2.5 cm per hour for sand, and well stabilized and aggregated soil structures.

Percolation is the downward movement of water in soil and will eventually carry with it clay, humus and nutrients, primarily cations, out of the range of plant roots and result in acid soil conditions. In order of decreasing solubility, the leached nutrients are:

Calcium Magnesium, Sulfur, Potassium depending upon soil composition. Nitrogen usually little, unless nitrate fertilizer was applied recently. Phosphorous very little as its forms in soil are of low solubility.

In the United States percolation water due to rainfall ranges from zero inches just east of the Rocky Mountains to twenty or more inches in the Appalachian Mountains and the north coast of the Gulf of Mexico.

At suctions less than one-third bar, water moves in all directions in “unsaturated flow” at a rate that is dependent on the square of the diameter of the water filled pores. Water is pushed by pressure gradients, from point of its application where it is saturated locally, and pulled by capillary action due to adhesion force of water for the soil solids, producing a suction gradient from wet toward drier soil. Doubling the diameter of the pores increases the the flow rate by a factor of four. Large pores drained by gravity and not filled with water do not greatly increase the flow rate for unsaturated flow. Water flow is primarily from coarse textured soil into fine-textured soil and moves most slowly through fine-textured soils such a clay.

Of equal importance to the storage and movement of water in soil is the means by which plants acquire it and their nutrients. Ninety percent of water is taken up by plants as passive absorption caused by the pulling force of water evaporating (transpiring) from the long column of water that leads from its roots to its leaves. In addition, the high concentration of salts within the plant roots create an osmotic pressure gradient that pushes soil water into the roots. Osmotic absorption becomes more important during times of low water transpiration at night (lower temperatures) or due to high humidity during the day. It is the processes which causes guttation.

Root extension is vital for plants survive. A study of a single winter rye plant grown for four months in one cubic foot of loam soil showed that the plant developed 13,800,000 roots of 385 miles and 2,550 square feet and 14 billion hair roots of 6,600 miles and 4,320 square feet, for a total surface area of 6,870 square feet. The total surface area of the loam soil was estimated to be 560,000 square feet. In other words the roots were in contact with only1.2% of the soil. Roots must seek out water as the unsaturated flow of water in soil can move only at a rate of up to 2.5 cm per day, as a result they are constantly dying and growing, seeking out high concentrations of soil moisture. Soil atmosphere is also important as very high concentrations of carbon-dioxide are toxic and without adequate oxygen the roots die. Hence, a proper balance of soil moisture and air space is vital to plant health.

Insufficient soil moisture to the point of wilting will cause permanent damage and crop yields will suffer. When grain sorghum was exposed to soil suction as low as 13.0 bar during the seed head emergence through bloom and seed set stages of growth, the production was reduced by 34%. Only a small fraction (0.1% to 1%) of the water used by a plant is held within the plant. Transpiration of water from the plant is the majority of the water use, while evaporation from the soil surface is also substantial. Transpiration plus evaporative soil moisture loss is called evapotranspiration. Evapotranspiration, plus water held in the plant totals to consumptive use. The total water use in an agricultural field includes runoff, drainage, and consumptive use. The use of loose mulches will reduce evaporative losses for a period after a field is irrigated but in the end the total evaporative loss will approach that of an uncovered soil. The benefit from mulch is to keep the moisture available during the seedling stage. Water use efficiency is measured by “transpiration ratio” which is the ratio of the total water transpired by a plant to the dry weight of the harvested plant at a particular locale. Alfalfa may have a transpiration ratio of 500 (for a particular location) and as a result 500 kilograms of water will produce one kilogram of dry alfalfa. Transpiration ratios for crops range from 300 to 700.

End of section references are primarily from Soils: An Introduction to Soils and Plant Growth and will be added later.Zedshort (talk) 17:03, 18 April 2012 (UTC)

The tables, numbered and bulleted lists did not come out correctly in the above but I can work it out later.Zedshort (talk) 17:05, 18 April 2012 (UTC)

Chemical and colloidal properties and nutrients[edit]

This article needs a section on nutrients, humus, clay and pH. A separate section on humus still seems appropriate Zedshort (talk) 22:20, 1 April 2012 (UTC)

Done

Nutrients[edit]

This article needs a section on nutrients Zedshort (talk) 15:14, 23 April 2012 (UTC)

Done

This section's subject matches another article's topic Plant nutrition . I was hoping these could be merged. thanks. Sidelight12 (talk) 15:19, 27 July 2012 (UTC)

I tend to believe the article here should be complete and stand on it's own to make the article complete, interesting, but a bit long. The article on nutrition could be greatly expanded. Zedshort (talk) 21:57, 12 August 2012 (UTC)

Work to be done[edit]

I have parsed this article many times, trying to make the reading flow and get the reading ease at least above 30 on the Flesch Reading Ease Index.

The article may seem a little long by most standards but at least it is complete and readable on several visits. Some parts might be moved to separate articles, such as the soil taxonomy, soil remediation sections.

I failed to provide sufficient references but will come back to that task later. I hope that for every reference to a physical copy that exists on some remote research library shelf another from a stable, reliable website such as the USDA might be provided.

There is a need for more illustrations, such as that of the structure of various clays.

Also, mention needs to be made of Terra Preta soil w.r.t. carbon and the buffering of ions in soil. Should it be in the organic section, the clay section or soil remediation section? Zedshort (talk) 21:47, 12 August 2012 (UTC)

I think this article can try for a nomination, and it looks complete in its subject coverage. There are usually a lot of short articles around, that can be linked to, to ease the overlap of writing, and ready references for further use. I've found this in other articles. Sidelight12 (talk) 16:22, 27 August 2012 (UTC)

I put a good article nominee template up. The subject has a lot of depth. English variant consistency won't matter: it doesn't add any value. I think the only concerns for this article are readability, inline sources and wikilinks to other articles. There are more than enough sources in the reference section, and I recommend an inline citation template where a line might need one, so work can be focused there. I think the review will give further insight to what it takes for a featured article. Sidelight12 Talk 14:32, 25 October 2012 (UTC)

  • you can remove the template, or try it for another class, if it is not time. Sidelight12 Talk 14:46, 25 October 2012 (UTC)

Tertiary / Pleistocene[edit]

Quote:

"Little of the soil of planet Earth is older than the Tertiary and none is older than the Pleistocene."

But the Pleistocene began 2.8 mya and the Tertiary began 65 mya. Rodri316 (talk) 18:05, 15 August 2012 (UTC)

I see your point. It needs to be switched about. Why don't you go ahead and do that. Zedshort (talk) 04:03, 16 August 2012 (UTC)
Because I don't know if it has to be switched around. Rodri316 (talk) 21:56, 17 August 2012 (UTC)
I made the switch and added a bit on fossilised soils. Mikenorton (talk) 07:02, 18 August 2012 (UTC)


Is it time to protect this article?[edit]

I have notice an amount of outright vandalism and some less than helpful but probably good faith efforts to edit the article. I hope others will contribute but maybe, since the article is nearing completion, it is time to make the article semi-protected so as to stop interference and stabilize the article? I know nothing of the procedure. The article is nearing completion but still needs work from others. Zedshort (talk) 02:03, 15 September 2012 (UTC)

I don't think it's that bad yet. But you can always propose it for semi-protection at the edit protection noticeboard and see what the experienced folks there think. --Yngvadottir (talk) 12:14, 15 September 2012 (UTC)

Turgid Writing[edit]

The user Soilcare (no longer active) inserted the following:

"But the onset of anoxic conditions within the soil can alter phosphorus equilibria through the solubilisation of redox sensitive mineral constituents and the simultaneous release of associated (adsorbed or co-precipitated) P anions."

I have read this many times and cannot understand it. I ran the text through a readability calculation tool at http://www.online-utility.org/english/readability_test_and_improve.jsp and found the writing to be too high to be practical in a WP article. It would require 26 years of education to understand this on the first read. The Flesch Reading Ease index is -14 which is too low. If it cannot be made readable at at the 14th through 16th year of education level I propose it be deleted. Zedshort (talk) 16:56, 20 October 2012 (UTC)

Surprisingly I do understand it (although perhaps it's more accurate to say that I think that I do), so those geochemistry lectures back in the '70s actually did do something. Perhaps something like "A change to anoxic conditions, however, tends to cause the release of Phosphorous ions from the soil." All the rest is probably superfluous here. Mikenorton (talk) 17:44, 20 October 2012 (UTC)

GA Review

Toolbox

See WP:DEADREF
for dead URLs

This review is transcluded from Talk:Soil/GA1. The edit link for this section can be used to add comments to the review.

Reviewer: TheSpecialUser (talk · contribs) 00:30, 27 October 2012 (UTC)

Since I'm busy with real life, I've been doing reviews which can only be completed at a glance. I'm sorry to say but this article is far away from GA standards. Here are the 3 basic reasons behind it:

  • The article is well detailed but still I feel that a vast topic like this needs additional 10-20K words or more
  • The lead is way too big in comparison with the article. Few things which are in the lead are not covered in the later part of the article which is a problem. Anything in the lead should be covered later in the article with more details and lead should be summary of the article per WP:LEAD
  • There is lack of refs. This is the main reason for the failure. The article is full of unsourced material and thus it is extremely tough to verify the content and to track down any vandalism. We need references to WP:RS in order to verify the content and this article has 70% of its content as unsourced. To get this up to GA level, each and every fact in the article should have at least one reliable source using well formatted citation.

Unfortunately, these issues cannot be addressed in 3-4 months as the topic is too complex and big. Sorry to say but I've to quickly fail it. Once addressed the mammoth issues raised above, anyone can go for another nom. Thanks! TheSpecialUser TSU 00:30, 27 October 2012 (UTC)

  • I re-read the lead and find there is still redundancy that makes the reading plod along and seem as if it is too long. Otherwise the lead needs to mention Classification, Uses, Degradation, and Reclamation some of which would need only one line. Soil Uses seems a bit trivial and probably does not need expanding. Degradation and Reclamation are large subjects and probably need their own articles with a brief overview here rather that going into specific examples in this article. One subtopic missing is Terra Preta or soil carbon of an anthropogenic origin and its usefulness w.r.t. buffering of soil in tropical climates where clay and humic components do not exist. I laid out the article following the table of contents of one of the two sources I have on my desk which is of course written in the light of agriculture. I can't see any other major sections that might be added to expand the article without straying too far into the subject of agriculture with the exception perhaps of Soil Testing which again is directed toward "correcting" the soil to improve its agricultural use. I have to go through and provide more references to the parts I wrote. Will do. Zedshort (talk) 16:38, 31 October 2012 (UTC)


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