Soil classification
Encyclopedia
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
s based on distinguishing characteristics as well as criteria that dictate choices in use.
Overview
Soil classification is a dynamic subject, from the structure of the system itself, to the definitions of classes, and finally in the application in the field. Soil classification can be approached from the perspective of soil as a material and soil as a resource.Engineering
Engineers, typically geotechnical engineers, classify soils according to their engineering properties as they relate to use for foundation support or building material. Modern engineering classification systems are designed to allow an easy transition from field observations to basic predictions of soil engineering properties and behaviors.The most common engineering classification system for soils in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
is the Unified Soil Classification System
Unified Soil Classification System
The Unified Soil Classification System is a soil classification system used in engineering and geology to describe the texture and grain size of a soil. The classification system can be applied to most unconsolidated materials, and is represented by a two-letter symbol...
(USCS). The USCS has three major classification groups: (1) coarse-grained soils (e.g. sands and gravels); (2) fine-grained soils (e.g. silts and clays); and (3) highly organic soils (referred to as "peat
Peat
Peat is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world...
"). The USCS further subdivides the three major soil classes for clarification.
Other engineering soil classification systems in the States include the AASHTO Soil Classification System
AASHTO Soil Classification System
The AASHTO Soil Classification System was developed by the American Association of State Highway and Transportation Officials, and is used as a guide for the classification of soils and soil-aggregate mixtures for highway construction purposes...
and the Modified Burmister (See biographical sketch of Prof. Donald Burmister
Donald Burmister
Donald M. Burmister was a professor of civil engineering and a pioneer in the field of soil mechanics and geotechnical engineering.- Career :Donald Burmister served as faculty member at Columbia University for 34 years, beginning in 1929...
http://www.civil.columbia.edu/ling/burmister/burmister.html).
A full geotechnical engineering soil description will also include other properties of the soil including color, in-situ moisture content, in-situ strength, and somewhat more detail about the material properties of the soil than is provided by the USCS code.
Soil science
Soil morphology
Soil morphology is the field observable attributes of the soil within the various soil horizons and the description of the kind and arrangement of the horizons. C.F...
), behaviour, or genesis
Pedogenesis
Pedogenesis is the science and study of the processes that lead to the formation of soil ' and first explored by the Russian geologist Vasily Dokuchaev , the so called grandfather of soil science, who determined that soil formed over time as a consequence of...
, results in classes that can be interpreted for many diverse uses. Differing concepts of pedogenesis, and differences in the significance of morphological features to various land uses can affect the classification approach. Despite these differences, in a well-constructed system, classification criteria group similar concepts so that interpretations do not vary widely. This is in contrast to a technical system approach to soil classification, where soils are grouped according to their fitness for a specific use and their edaphic
Edaphic
Edaphic is a nature related to soil. Edaphic qualities may characterize the soil itself, including drainage, texture, or chemical properties such as pH. Edaphic may also characterize organisms, such as plant communities, where it specifies their relationships with soil...
characteristics.
Natural system approaches to soil classification, such as the French Soil Reference System (Référentiel pédologique français) are based on presumed soil genesis. Systems have developed, such as USDA soil taxonomy
USDA soil taxonomy
USDA Soil Taxonomy developed by United States Department of Agriculture and the National Cooperative Soil Survey provides an elaborate classification of soil types according to several parameters and in several levels: Order, Suborder, Great Group, Subgroup, Family, and Series.- Example of...
and the World Reference Base for Soil Resources
World Reference Base for Soil Resources
The World Reference Base for Soil Resources is the international standard taxonomic soil classification system endorsed by the International Union of Soil Sciences . It was developed by an international collaboration coordinated by the International Soil Reference and Information Centre and...
, which use taxonomic criteria involving soil morphology and laboratory tests to inform and refine hierarchical
Hierarchy
A hierarchy is an arrangement of items in which the items are represented as being "above," "below," or "at the same level as" one another...
classes.
Another approach is numerical classification, also called ordination
Ordination (statistics)
In multivariate analysis, ordination is a method complementary to data clustering, and used mainly in exploratory data analysis . Ordination orders objects that are characterized by values on multiple variables so that similar objects are near each other and dissimilar objects are farther from...
, where soil individuals are grouped by multivariate statistical methods such as cluster analysis. This produces natural groupings without requiring any inference about soil genesis.
In soil survey
Soil survey
Soil survey, or soil mapping, is the process of classifying soil types and other soil properties in a given area and geo-encoding such information. It applies the principles of soil science, and draws heavily from geomorphology, theories of soil formation, physical geography, and analysis of...
, as practiced in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, soil classification usually means criteria based on soil morphology
Soil morphology
Soil morphology is the field observable attributes of the soil within the various soil horizons and the description of the kind and arrangement of the horizons. C.F...
in addition to characteristics developed during soil formation. Criteria are designed to guide choices in land use
Land use
Land use is the human use of land. Land use involves the management and modification of natural environment or wilderness into built environment such as fields, pastures, and settlements. It has also been defined as "the arrangements, activities and inputs people undertake in a certain land cover...
and soil management
Soil management
Soil management concerns all operations, practices and treatments used to protect soil and enhance its performance.-Practices:Soil management practices that affect soil quality:...
. As indicated, this is a hierarchical system that is a hybrid of both natural and objective criteria. USDA soil taxonomy
USDA soil taxonomy
USDA Soil Taxonomy developed by United States Department of Agriculture and the National Cooperative Soil Survey provides an elaborate classification of soil types according to several parameters and in several levels: Order, Suborder, Great Group, Subgroup, Family, and Series.- Example of...
provides the core criteria for differentiating soil map units. This is a substantial revision of the 1938 USDA soil taxonomy
1938 USDA soil taxonomy
The 1938 USDA soil taxonomy was a soil classification system adopted by the United States Department of Agriculture, now obsolete. The classification system used previously was developed and published in 1936 by C.F. Marbut, who was chief of the U.S. Soil Survey at that time. A drastic...
which was a strictly natural system. Soil taxonomy based soil map units are additionally sorted into classes based on technical classification systems. Land Capability Classes
Land use capability map
Land use capability maps are maps created to represent the potential uses of a "unit" of land. They are measured using various indicators, although the most common are five physical factors...
, hydric soil
Hydric soil
A hydric soil is a soil that formed under conditions of saturation, flooding, or ponding long enough during the growing season to develop anaerobic conditions in the upper part....
, and prime farmland
Prime farmland
Prime farmland is a designation assigned by U.S. Department of Agriculture defining land that has the best combination of physical and chemical characteristics for producing food, feed, forage, fiber, and oilseed crops and is also available for these land uses....
are some examples.
In addition to scientific soil classification systems, there are also vernacular
Vernacular
A vernacular is the native language or native dialect of a specific population, as opposed to a language of wider communication that is not native to the population, such as a national language or lingua franca.- Etymology :The term is not a recent one...
soil classification systems. Folk taxonomies have been used for millennia, while scientifically based systems are relatively recent developments.
See also
- AASHTO Soil Classification SystemAASHTO Soil Classification SystemThe AASHTO Soil Classification System was developed by the American Association of State Highway and Transportation Officials, and is used as a guide for the classification of soils and soil-aggregate mixtures for highway construction purposes...
- Australian Soil ClassificationAustralian Soil ClassificationThe Australian Soil Classification is the classification system currently used to describe and classify soils in Australia. It is a general-purpose, hierarchical classification system, and consists of five categorical levels from the most general to the most specific: order, suborder, great group,...
- Canadian system of soil classificationCanadian system of soil classificationThe Canadian system of soil classification is more closely related to the American system than any other. They differ in several ways. The Canadian system is designed to cover only Canadian soils. The Canadian system dispenses with a sub-order hierarchical level. Solonetzic and Gleysolic soils are...
- French soil classificationFrench soil classificationAn English translation of soils defined in the "référentiel pedologique français" can be done that way. it is very relevant for european soils :Alocrisol humicAlocrisol typicAluandosol haplicAluandosol humicAluandosol perhydricAnthroposol artificial...
- FAO soil classificationFAO soil classificationThe Food and Agriculture Organization of the United Nations developed a supra-national classification, also called World Soil Classification, which offers useful generalizations about soils pedogenesis in relation to the interactions with the main soil-forming factors. It was first published in...
- International Committee on Anthropogenic SoilsInternational Committee on Anthropogenic SoilsThe International Committee on Anthropogenic Soils defines its mission as follows. "ICOMANTH is charged with defining appropriate classes in soil taxonomy for soils that have their major properties derived from human activities...
(ICOMANTH) - Soil texture classification
- USDA soil taxonomyUSDA soil taxonomyUSDA Soil Taxonomy developed by United States Department of Agriculture and the National Cooperative Soil Survey provides an elaborate classification of soil types according to several parameters and in several levels: Order, Suborder, Great Group, Subgroup, Family, and Series.- Example of...
- World Reference Base for Soil Resources (WRB)World Reference Base for Soil ResourcesThe World Reference Base for Soil Resources is the international standard taxonomic soil classification system endorsed by the International Union of Soil Sciences . It was developed by an international collaboration coordinated by the International Soil Reference and Information Centre and...
Further reading
- Eswaran, H., Rice, T., Ahrens, R., & Stewart, B. A. (Eds.). (2002). Soil classification : a global desk reference. Boca Raton, Fla.: CRC Press.
Current international system
- Buol, S.W., Southard, R.J., Graham, R.C., and McDaniel, P.A. (2003). Soil Genesis and Classification, 5th Edition. Iowa State Press - Blackwell, Ames, IA.
- Driessen, P., Deckers, J., Spaargaren, O., & Nachtergaele, F. (Eds.). (2001). Lecture notes on the major soils of the world. Rome: FAO.
- FAO. (1998). World Reference Base for Soil Resources. Rome: Food and Agriculture Organization of the United Nations.
Current natural systems
- Agriculture Canada Expert Committee on Soil Survey. (1987). The Canadian system of soil classification (2nd ed.). Ottawa: Canadian Government Publishing Centre.
- Avery, B. W. (1980). Soil classification for England and Wales: higher categories. Cranfield, England: Cranfield University, Soil Survey & Land Research Centre.
- Baize, D., & Girard, M. C. (Eds.). (1995). Référentiel pédologique 1995. Paris: Institut National de la Recherche Agronomique.
- Baize, D., & Girard, M. C. (Eds.). (1998). A sound reference base for soils: The "Référentiel Pédologique" (English translation by Hodgson J.M., Eskenazi N.R., & Baize D. ed.). Paris: Institut National de la Recherche Agronomique.
- Hewitt, A. E. (1992). Soil classification in New Zealand: legacy and lessons. Australian Journal of Soil Research, 30, 843-854.
- Isbell, R. F. (1996). The Australian soil classification. Collingwood, Victoria, Australia: CSIRO.
- Soil Classification Working Group. (1991). Soil classification: a taxonomic system for South Africa. Pretoria: Department of Agricultural Development, RSA.
- Soil Survey Staff. (1999). Soil taxonomy: a basic system of soil classification for making and interpreting soil surveys (2nd ed.). Washington, DC: US Department of Agriculture Soil Conservation Service.
Current technical systems
- Boorman, D. B., Hollis, J. M., & Lilly, A. (1995). Hydrology of soil types: a hydrologically-based classification of the soils of the United Kingdom (No. 126): UK Institute of Hydrology.
- Klingebiel, A. A., & Montgomery, P. H. (1961). Land capability classification. Washington, DC: US Government Printing Office.
- Sanchez, P. A., Palm, C. A., & Buol, S. W. (2003). Fertility capability soil classification: a tool to help assess soil quality in the tropics. Geoderma, 114(3-4), 157-185.
- American Society for Testing and Materials, 1985, D 2487-83, Classification of Soils for Engineering Purposes: Annual Book of ASTM Standards. Vol. 04.08, pp 395-408.
Earlier systems of historical interest
- Baldwin, M., Kellogg, C. E., & Thorp, J. (1938). Soil classification. In Soils and men: Yearbook of agriculture (pp. 979-1001). Washington, DC: U.S. Department of Agriculture.
- Simonson, R. W. (1989). Historical aspects of soil survey and soil classification with emphasis on the United States, 1899-1970. Wageningen, NL: International Soil Reference and Information CentreInternational Soil Reference and Information CentreWorld Soil Information, established in 1964 is an independent foundation with a global mandate, funded by the Netherlands Government, and with a strategic association with Wageningen University and Research Centre.Our aims:...
(ISRIC).
Principles
- Butler, B. E. (1980). Soil classification for soil survey. Oxford: Oxford Science Publications.Science, 96,
- Cline, M. G. (1949). Basic principles of soil classification. Soil Science, 67(2), 81-91.
- Cline, M. G. (1963). Logic of the new system of soil classification. Soil 17-22.
- Webster, R. (1968). Fundamental objections to the 7th approximation. Journal of Soil Science, 19, 354-366.
- Terzaghi Karl (1924). Soil Mechanics in Engineering Practice, Wiley-Interscience; 3 Sub-edition (January 1996, ISBN: 0471086584)
Numerical classification
- McBratney, A. B., & de Gruijter, J. J. (1992). A continuum approach to soil classification by modified fuzzy k-means with extragrades. Journal of Soil Science, 43(1), 159-175.