Talk:Soil profile

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[edit] revision needed

The current profile graphic definitely needs to be replaced. The E horizon on the jpg should be an R horizon. If we are going to describe an O horizon, we need one on the jpg. Paleorthid 20:59, 1 April 2006 (UTC)

The O horizon problem, mentioned above was reverted as vandalism but we still have some issues to clear up here. Since these horizon designations are inconsistent with the formally established O-A-E-B-C-RorD horizon designations and descriptions described in the soil horizon article, I have asked for the reference supporting the simplistic A-E system depicted here. It appears to be a folk or vernacular soil horizon designation system, and I don't have a problem with that per se, but it needs to be sorted out. Note that the soil horizon article is also lacking references at this point. Paleorthid 17:58, 2 April 2006 (UTC)

I was the person that contributed both the graphic and the labeling, its based on various gardening books, I don't remember which off hand, but these are fairly standard in horticultural books that I've seen, and reflect the soil horizons I've observed in various gardens and allotments. maybe this article needs to be moved to 'garden soil profile' or similar in order to distinguish it from more the scientific labelling system you have in mind? quercus robur 19:08, 2 April 2006 (UTC)

If its fairly standard, between the two of us we should be able to reference it. Please disregard my "jpg needs replacing" that I started out with on this. Rather than move the information, I would much prefer to expand the article. Soil is soil and knowing it and using it intelligently necessarily predates any formal science. Look at terra preta, for instance, probably the single most important discovery in "soil science" and figured out before the Greeks invented science. Paleorthid 20:03, 2 April 2006 (UTC)

I was unable to locate a reference in support of the previous jpg. I have placed a more commonly used graphic and revised the text accordingly. -- Paleorthid 04:55, 1 June 2006 (UTC)

[edit] raw material for article

In excavating the soil to any appreciable depth, it is necessary to dig through distinct zones called horizons.

The morphology of these horizons is called the soil profile. Each soil type has a distinctive profile that is determined by the particular combination of factors that produced the soil.

By the time most forest and prairie soils are mature they have developed 3 major horizons, designated (from the top down) A, B, and C. The underlying bedrock (usually but not always the true parent material) is called the R horizon.

The A horizon is the zone of leaching (eluviation). Roots, bacteria, fungi, and small animals (for example, earthworms and nematodes) are most abundant in this horizon. It is poor in soluble substances and has lost some clay and some iron and aluminum oxides.

The B horizon is the zone of accumulation (illuviation). It is less abundant in living matter. It is higher in clay and in iron and aluminum oxides, and is thus stickier when wet and harder when dry.

The C horizon consists of weathered rock material, often true parent material. When hardpans are present (as in prairie soils and the soils of wheat and corn raising regions) they are a part of this horizon.

The R horizon is the underlying consolidated bedrock, such as limestone, granite, or sandstone, from which the overlying horizons were formed.

Often it is desirable to subdivide the A or B horizons further. They are then each divided from top to bottom into 3 strata: A1, A2, and A3; B1, B2, and B3. The A1 stratum is often dark in color, owing to its high content of organic matter. The middle stratum of a horizon (A2 or B2) is always the typical one for that horizon; the others tend to grade into their neighbors.

The layer of partially decomposed duff immediately above the A horizon is referred to as the O horizon. A zone of strong elluviation at the bottom of the A horizon is designated an E horizon.

Not all profiles show complete development, and soils that have been used for agricultural purposes for long periods of time are especially likely to be lacking in 1 or more of the uppermost horizons. Their most prominent feature is the plow horizon–the horizon that has been repeatedly disrupted by plowing, disking, and harrowing.

Soils with well-developed profiles are called zonal, or normal soils. Zonal soils are found where the factors of soil formation are conducive to profile development. Azonal soils have no distinct profile and are frequently alluvial (water deposited) or colluvial (gravity deposited) soils of recent origin. Intrazonal soils are those that are limited in extent and are under the control of a local factor, such as high salt content or poor drainage, that does not permit the development normally associated with zonal soils.

Some soils have been truncated. That is, they consist of only a portion of the original profile, the upper portion having been lost through erosion. Most agricultural soils are truncated remains of the original soil that developed under natural vegetation, and some are completely new, having been formed by the addition of soil or organic matter from another location in order to increase productivity. At times, truncated soils are "buried" under soil deposited by wind or water.

Source: Soil Survey Manual

Each horizon within a specific soil can have significantly different characteristics such as depth, texture, bulk density, mineral composition, and chemical properties that may result in differing waste transport and attenuative characteristics. Horizon boundary characteristics can adversely affect vertical movement (percolation) of soil liquids. Such boundary characteristics include abrupt changes in texture or structure, such as clay or sand layers or the presence of hard pans (i.e., a hardened soil layer in the lower A or in the B horizon caused by cementation of soil particles with organic matter or with materials such as silica, sesquioxides, or calcium carbonate and whose hardness does not change appreciably with changes in water content).

Source: [1]

[edit] Proposed article merger

I support an article merger, with the following qualifier. Rather than merging soil profile with soil horizon, it makes more sense to merge soil horizon into soil profile:

Soil profile is a WPCD candidate article, soil horizon is not. I sense this is because:
The phrase, soil profile, has higher recognition. For example, the search term "soil profile" gets 1,040,000 Google hits, "soil horizon" gets 158,000.
Soil profile, created in December 2002, is the more established article. Soil horizon was created in February, 2005.
Soil horizon is a subsidiary concept to soil profile. -- Paleorthid 18:52, 13 September 2006 (UTC)