Editing Soil science

{{Short description|Study of soil as a natural resource on the surface of Earth}}
{{Use dmy dates|date=June 2023}}
[[File:Soil sci.jpg|thumb|A soil scientist examining horizons within a soil profile]]

'''Soil science''' is the study of [[soil]] as a [[natural resource]] on the surface of the [[Earth]] including [[soil formation]], [[soil classification|classification]] and [[Soil survey|mapping]]; [[Soil physics|physical]], [[Soil chemistry|chemical]], [[Soil biology|biological]], and fertility properties of soils; and these properties in relation to the use and [[Soil management|management of soils]].<ref name=":0">Jackson, J. A. (1997). Glossary of Geology (4. ed.). Alexandria, Virginia: American Geological Institute. p 604. {{ISBN|0-922152-34-9}}</ref>

The main branches of soil science are ''[[pedology]]'' ― the study of formation, chemistry, morphology, and classification of soil ― and ''[[edaphology]]'' ― the study of how soils interact with living things, especially plants. Sometimes terms which refer to those branches are used as if synonymous with soil science. The diversity of names associated with this discipline is related to the various associations concerned.  Indeed, engineers, [[agronomy|agronomists]], [[chemist]]s, [[geologist]]s, [[physical geography|physical geographers]], [[ecologists]], [[biologist]]s, [[microbiologist]]s, [[forestry|silviculturists]], [[public health|sanitarians]], [[Archaeology|archaeologists]], and specialists in [[regional planning]], all contribute to further knowledge of soils and the advancement of the soil sciences.<ref name=":0" />

Soil scientists have raised concerns about how to preserve soil and arable land in a world with a growing population, possible future [[Water scarcity|water crisis]], increasing per capita [[List of countries by food energy intake|food consumption]], and [[land degradation]].<ref>{{cite journal | display-authors = 1 | author = H. H. Janzen | author2 = P.E. Fixen | author3 = A. J. Franzluebbers | author4 = J. Hattey | author5 = R. C. Izaurralde | author6 = Q. M. Ketterings | author7 = D. A. Lobb | author8 = W. H. Schlesinger | name-list-style = amp | date = 2011 | title = Global Prospects Rooted in Soil Science | url = https://www.soils.org/publications/sssaj/articles/75/1/1 | journal = Soil Science Society of America Journal | volume = 75 | issue = 1| page = 1 | doi = 10.2136/sssaj2009.0216 | bibcode = 2011SSASJ..75....1J | doi-access = free }}</ref>

==Fields of study==
Soil occupies the [[pedosphere]], one of [[Earth's spheres]] that the [[Earth science|geosciences]] use to organize the Earth conceptually. This is the conceptual perspective of [[pedology]] and [[edaphology]], the two main branches of soil science. Pedology is the study of soil in its natural setting. Edaphology is the study of soil in relation to soil-dependent uses. Both branches apply a combination of [[soil physics]], [[soil chemistry]], and [[soil biology]]. Due to the numerous interactions between the [[biosphere]], [[atmosphere]] and [[hydrosphere]] that are hosted within the pedosphere, more integrated, less soil-centric concepts are also valuable. Many concepts essential to understanding soil come from individuals not identifiable strictly as soil scientists. This highlights the interdisciplinary nature of soil concepts.

==Research==
Exploring the diversity and dynamics of soil continues to yield fresh discoveries and insights. New avenues of soil research are compelled by a need to understand soil in the context of [[climate change]],<ref name="raul" /><ref>{{cite web |last=Pielke |first=Roger |date=12 December 2005 |title=Is Soil an Important Component of the Climate System? |archive-url=https://web.archive.org/web/20060908124853/http://climatesci.atmos.colostate.edu/2005/12/19/is-soil-an-important-component-of-the-climate-system/ |archive-date=8 September 2006 |work=The Climate Science Weblog |access-date=19 April 2012|url=http://climatesci.atmos.colostate.edu/2005/12/19/is-soil-an-important-component-of-the-climate-system/ }}</ref> [[greenhouse gas]]es, and [[carbon sequestration]].<ref name="raul">{{cite journal |last1=Ochoa-Hueso |first1=R |last2=Delgado-Baquerizo |first2=M |last3=King |first3=PTA |last4=Benham |first4=M |last5=Arca |first5=V |last6=Power |first6=SA |title=Ecosystem type and resource quality are more important than global change drivers in regulating early stages of litter decomposition |journal=Soil Biology and Biochemistry |date=February 2019 |volume=129 |pages=144–152 |doi=10.1016/j.soilbio.2018.11.009 |bibcode=2019SBiBi.129..144O |s2cid=92606851 |hdl=10261/336676 |hdl-access=free }}</ref> Interest in maintaining the planet's biodiversity and in exploring [[terra preta|past cultures]] has also stimulated renewed interest in achieving a more refined understanding of soil.

==Mapping==
{{excerpt|Soil survey}}

==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]].

==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>

==Areas of practice==
Academically, soil scientists tend to be drawn to one of five areas of specialization: [[Soil microbiology|microbiology]], [[pedology]], [[edaphology]], [[Soil physics|physics]], or [[Soil chemistry|chemistry]]. Yet the work specifics are very much dictated by the challenges facing our civilization's desire to sustain the land that supports it, and the distinctions between the sub-disciplines of soil science often blur in the process. Soil science professionals commonly stay current in soil chemistry, soil physics, soil microbiology, pedology, and applied soil science in related disciplines.

One exciting effort drawing in soil scientists in the U.S. {{As of|2004|lc=on}} is the Soil Quality Initiative. Central to the Soil Quality Initiative is developing indices of soil health and then monitoring them in a way that gives us long-term (decade-to-decade) feedback on our performance as stewards of the planet. The effort includes understanding the functions of soil microbiotic crusts and exploring the potential to sequester atmospheric carbon in [[soil organic matter]]. Relating the concept of agriculture to [[soil quality]], however, has not been without its share of controversy and criticism, including critiques by Nobel Laureate [[Norman Borlaug]] and World Food Prize Winner [[Pedro A. Sanchez|Pedro Sanchez]].

A more traditional role for soil scientists has been to map soils. Almost every area in the United States now has a published [[soil survey]], including interpretive tables on how soil properties support or limit activities and uses. An internationally accepted soil taxonomy allows uniform communication of soil characteristics and [[soil functions]]. National and international soil survey efforts have given the profession unique insights into landscape-scale functions. The landscape functions that soil scientists are called upon to address in the field seem to fall roughly into six areas:

* '''Land-based treatment of wastes'''
**[[Septic system]]
**[[Manure]]
**Municipal [[biosolids]]
**Food and fiber processing waste
* '''Identification and protection of environmentally critical areas'''
**Sensitive and unstable soils
**[[Wetland]]s
**Unique soil situations that support valuable [[habitat conservation|habitat]], and [[ecosystem diversity]]
* '''Management for optimum land productivity'''
**[[Silviculture]]
**[[Agronomy]]
***[[Fertilizer|Nutrient]] management
***[[Irrigation|Water]] management
**Native vegetation
**[[Grazing]]
* '''Management for optimum water quality'''
**[[Stormwater]] management
**[[Sediment]] and [[erosion]] control
* '''Remediation and restoration of damaged lands'''
**[[Mine reclamation]]
**Flood and storm damage
**Contamination
* '''Sustainability of desired uses'''
**[[Soil conservation]]

There are also practical applications of soil science that might not be apparent from looking at a published soil survey.

* '''[[Radiometric dating#Short-range dating techniques|Radiometric dating]]''': specifically a knowledge of local pedology is used to date prior activity at the site
**[[Stratification (archeology)]] where soil formation processes and preservative qualities can inform the study of [[archaeological site]]s
**[[List of geological phenomena|Geological phenomena]]
***[[Landslide]]s
***[[Active faults]]
* '''Altering soils to achieve new uses'''
**[[Radioactive waste#Vitrification|Vitrification]] to contain [[radioactive waste]]s
**Enhancing [[soil life|soil microbial]] capabilities in degrading contaminants ([[bioremediation]]).
**[[Carbon sequestration]]
** [[Environmental soil science]]
* [[Pedology]]
** [[Pedogenesis|Soil genesis]]
** [[Pedometrics]]
** [[Soil morphology]]
*** Soil micromorphology
** [[Soil classification]]
***[[USDA soil taxonomy]]
***[[World Reference Base for Soil Resources]]<ref name=WRB/>
* [[soil life|Soil biology]]
** [[Soil microbiology]]
* [[Soil chemistry]]
** Soil biochemistry
** Soil mineralogy
* [[Soil physics]]
** [[Pedotransfer function]]
** [[Soil mechanics]] and engineering
* Soil hydrology, [[hydropedology]]

===Fields of application in soil science===
* [[Climate change]]<ref name="raul" />
* [[Ecosystem]] studies
* [[Pedotransfer function]]
* [[Soil fertility]] / Nutrient management
* [[Soil management]]
* [[Soil survey]]
* Standard methods of analysis
* [[drainage basin|Watershed]] and [[wetland]] studies
* [[Land Suitability classification]]

===Related disciplines===
* [[Agricultural sciences]]
** [[Agricultural soil science]]
** [[Agrophysics]] science
** [[Irrigation]] management
* [[Anthropology]]
** [[Stratification (archeology)|archaeological stratigraphy]]
* [[Environmental science]]
** [[Landscape ecology]]
* [[Physical geography]]
** [[Geomorphology]]
* [[Geology]]
** [[Biogeochemistry]]
** [[Geomicrobiology]]
* [[Hydrology]]
** [[Hydrogeology]]
* [[Waste management]]
* [[Wetland]] science

== Depression storage capacity ==
Depression storage capacity, in soil science, is the ability of a particular area of land to retain water in its pits and depressions, thus preventing it from flowing.<ref>Hansen, Bjarne, Per Schjønning, and Erik Sibbesen. "[https://www.researchgate.net/profile/Per_Schjonning/publication/248301364_Roughness_indices_for_estimation_of_depression_storage_capacity_of_tilled_soil_surfaces/links/542aade90cf27e39fa8ee9f2.pdf Roughness indices for estimation of depression storage capacity of tilled soil surfaces] {{Webarchive|url=https://web.archive.org/web/20170825020315/https://www.researchgate.net/profile/Per_Schjonning/publication/248301364_Roughness_indices_for_estimation_of_depression_storage_capacity_of_tilled_soil_surfaces/links/542aade90cf27e39fa8ee9f2.pdf |date=25 August 2017 }}." Soil and Tillage Research 52.1 (1999): 103-111.</ref> Depression storage capacity, along with [[infiltration capacity]], is one of the main factors involved in [[Horton overland flow]], whereby water volume surpasses both infiltration and depression storage capacity and begins to flow horizontally across land, possibly leading to [[flood]]ing and [[soil erosion]]. The study of land's depression storage capacity is important in the fields of [[geology]], [[ecology]], and especially [[hydrology]].

==See also==

{{div col}}
* [[Agricultural soil science]]
*[[Agroecology]]
*[[Agronomy]]
*[[Agrophysics]]
*[[Australian Society of Soil Science Incorporated]] (ASSSI)
* [[Compost]]
* [[History of soil science]]
*[[International Soil Reference and Information Centre]] (ISRIC)
*[[International Union of Soil Sciences]] (IUSS)
*[[Liming (soil)]]
*[[List of Russian Earth scientists]]
*[[List of State Soil Science Associations]]
*[[List of State Soil Science Licensing Boards]]
*[[National Society of Consulting Soil Scientists]] (NSCSS)
*[[Resonant column test]]
* [[Soil biology]]
*[[Soil Science Society of America]] (SSSA)
*[[Soil value]]
*[[World Congress of Soil Science]] (WCSS)
{{div col end}}

==References==
{{Reflist}}
* Soil Survey Staff (1993). [https://web.archive.org/web/20061219225438/http://soils.usda.gov/technical/manual/contents/chapter1.html Soil Survey: Early Concepts of Soil.] (html) ''Soil Survey Manual USDA Handbook 18'', Soil Conservation Service. U.S. Department of Agriculture. URL accessed on 2004-11-30.
*{{cite book|author=Marion LeRoy Jackson|title=Soil Chemical Analysis: Advanced Course|url=https://books.google.com/books?id=VcEOK9QCkVEC&pg=PR5|year=2005|publisher=UW-Madison Libraries Parallel Press|isbn=978-1-893311-47-3|pages=5–}}

==External links==
*{{Commonscatinline|Soil science}}

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