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What is claypan? Is the term used the same the world over?
editWe need a discussion. Claypan is barely a technical term, is more in use as a colloquial term, and I expect there is regional differences in use as a result. I encounter the term claypan in my profession, and the term is most well established in the prairie states from Texas USA north into Canada. Here is my view through the knothole:
The claypan I encountered was especially extensive in South Dakota. All the claypan I mapped was associated with classic Solonetz development: sodium dispersion of silt and clay causing the subsoil (argillic) soil horizon to lose aggregate stability. Sodium tends not to accumulate in the climate east of the "lime line" in the USA. So by my thinking _if_ the term claypan is being applied for other-than-Solonetz in other regions, we will need to bring this out in the claypan article. For example, a "claypan" in an area with enough rainfall to develop ultisols (North Carolina, Georgia, ...) would be outside the use of the term as it is used in my western North America region. Ultisol claypans need a different management response than alfisol or mollisol claypans, the presence or absence of the sodium factor being the primary reason for this difference.
Compared to "just" clay, claypan is more susceptible to problems of poor infiltration. Rain events produce more runoff and more ponding water than just clay, problems develop more often than in just clay. In western North America, the most commonly occurring characteristic in a claypan landscape unit are bare clay slickspots within the unit. In my mapping days in South Dakota, if your land class unit didn't have slickspots, you would be challenged by the correlator to group it with claypan map units. But that's just one perspective: that sodium induced slickspots are fundamental to the claypan phenomenon. We need a world view for the article, does anybody have some favored references using the term claypan? Paleorthid (talk) 17:32, 11 January 2016 (UTC)
- Outside the US I can only found the term used in Australia, but the usage appears to be somewhat different [1]. Mikenorton (talk) 18:01, 11 January 2016 (UTC)
Best Sources
editrts WP:BESTSOURCES <reminder to self.
1) Definition: A dense compact layer in the subsoil having a much higher clay content than the overlaying material from which it is separated by a sharply defined boundary; formed by downward movement of clay or by synthesis of clay in place during soil formation. Claypans are usually hard when dry and plastic and sticky when wet. They usually impede the movement of water and air. cf. hardpan
Source: Society for Range Management. 1998. Glossary of terms used in range management, fourth edition. Edited by the Glossary Update Task Group, Thomas E. Bedell, Chairman.
2) "Clay pan" A hard and typically impermeable subsurface layer in a soil. Hardness is a function of the high clay content within a distinct clay-packed layer within a profile. Adapted from the more detailed definition of Pan in The Encyclopedia of Soil Science, 2008, Edited by Ward Chesworth.