Editing Soil science (section)

==History==
The earliest known [[soil classification]] system comes from China, appearing in the book ''[[Yu Gong]]'' (5th century BCE), where the soil was divided into three categories and nine classes, depending on its color, texture and hydrology.<ref>Arnold, R. ''et al''. (2009) [https://books.google.com/books?id=pL0GNDLy0bEC&q=Yugong&pg=PA340 A Handbook of Soil Terminology, Correlation and Classification] Earthscan, London, England.</ref>

Contemporaries [[Friedrich Albert Fallou]] (the German founder of modern soil science) and [[Vasily Dokuchaev]] (the Russian founder of modern soil science) are both credited with being among the first to identify soil as a resource whose distinctness and complexity deserved to be separated conceptually from geology and crop production and treated as a whole. As a founding father of soil science, Fallou has primacy in time. Fallou was working on the origins of soil before Dokuchaev was born; however Dokuchaev's work was more extensive and is considered to be the more significant to modern soil theory than Fallou's.

Previously, soil had been considered a product of chemical transformations of rocks, a dead substrate from which plants derive nutritious elements. Soil and [[bedrock]] were in fact equated. Dokuchaev considers the soil as a natural body having its own genesis and its own history of development, a body with complex and multiform processes taking place within it. The soil is considered as different from bedrock. The latter becomes soil under the influence of a series of soil-formation factors (climate, vegetation, country, relief and age). According to him, soil should be called the "daily" or outward horizons of rocks regardless of the type; they are changed naturally by the common effect of water, air and various kinds of living and dead organisms.<ref>Krasilnikov, N.A. (1958) [http://www.soilandhealth.org/01aglibrary/010112Krasil/010112krasil.intro.html Soil Microorganisms and Higher Plants] {{Webarchive|url=https://web.archive.org/web/20041112091351/http://www.soilandhealth.org/01aglibrary/010112Krasil/010112krasil.intro.html |date=12 November 2004 }}</ref>

A 1914 encyclopedic definition: "the different forms of earth on the surface of the rocks, formed by the breaking down or [[weathering]] of rocks".<ref>[[Wikisource:The New Student's Reference Work/4-0310]]</ref> serves to illustrate the historic view of soil which persisted from the 19th century. Dokuchaev's late 19th century soil concept developed in the 20th century to one of soil as earthy material that has been altered by living processes.<ref name=Buol73>{{cite book | last = Buol | first = S. W. | author2 = Hole, F. D. | author3 = McCracken, R. J. | name-list-style = amp | title = Soil Genesis and Classification  | edition = First | date = 1973 | publisher = Iowa State University Press | location = Ames, IA | isbn = 978-0-8138-1460-5  }}.</ref> A corollary concept is that soil without a living component is simply a part of Earth's outer layer.

Further refinement of the soil concept is occurring in view of an appreciation of energy transport and transformation within soil. The term is popularly applied to the [[lunar soil|material on the surface of the Earth's moon]] and Mars, a usage acceptable within a portion of the scientific community. Accurate to this modern understanding of soil is Nikiforoff's 1959 definition of soil as the "excited skin of the sub aerial part of the [[Earth's crust]]".<ref>{{cite journal  | author = C. C. Nikiforoff  | title = Reappraisal of the soil: Pedogenesis consists of transactions in matter and energy between the soil and its surroundings | journal = Science  | volume = 129  | pages = 186–196  | doi = 10.1126/science.129.3343.186  | date = 1959  | pmid = 17808687  | issue = 3343|bibcode = 1959Sci...129..186N }}</ref>