Editing Soil science (section)

==Classification==
{{main|soil classification}}
[[File:Global soils map USDA.jpg|thumb|upright=1.8|Map of global soil regions from the [[USDA]]]]
In 1998, the [[World Reference Base for Soil Resources]] (WRB) replaced the [[FAO soil classification]] as the international soil classification system. The currently valid version of WRB is the 4th edition, 2022.<ref name=WRB>{{Cite web|url = https://www3.ls.tum.de/boku/?id=1419|title = World Reference Base for Soil Resources, 4th edition|author=IUSS Working Group WRB|year = 2022|publisher = IUSS, Vienna}}</ref> The FAO soil classification, in turn, borrowed from modern soil classification concepts, including [[USDA soil taxonomy]].

WRB is based mainly on [[soil morphology]] as an expression of [[pedogenesis]]. A major difference with USDA soil taxonomy is that soil climate is not part of the system, except insofar as climate influences soil profile characteristics.

Many other classification schemes exist, including vernacular systems. The structure in vernacular systems is either nominal (giving unique names to soils or landscapes) or descriptive (naming soils by their characteristics such as red, hot, fat, or sandy). Soils are distinguished by obvious characteristics, such as physical appearance (e.g., [[Soil color|color]], [[Soil texture|texture]], [[landscape]] position), performance (e.g., [[Soil production function|production]] capability, flooding), and accompanying vegetation.<ref>{{cite web|archive-url=https://web.archive.org/web/20070306144700/http://forages.oregonstate.edu/is/ssis/main.cfm?PageID=168 |archive-date=6 March 2007
|title=Vernacular Systems |access-date=19 April 2012|url=http://forages.oregonstate.edu/is/ssis/main.cfm?PageID=168}}</ref> A vernacular distinction familiar to many is classifying texture as heavy or light. Light soil content and better structure take less effort to turn and cultivate. Light soils do not necessarily weigh less than heavy soils on an air dry basis, nor do they have more [[porosity]].