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Soil science

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File:Soil sci.jpg
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, classification and mapping; physical, chemical, biological, and fertility properties of soils; and these properties in relation to the use and management of soils.[1]

The diversity of names of disciplines associated with soil science is related to the various associations concerned. Indeed, engineers, agronomists, chemists, geologists, physical geographers, ecologists, biologists, microbiologists, silviculturists, sanitarians, archaeologists, and specialists in regional planning, all contribute to further knowledge of soils and the advancement of the soil sciences.[2]

Soil scientists have raised concerns about how to preserve soil and arable land in a world with a growing population, possible future water crisis, increasing per capita food consumption, and land degradation.[3]

Fields of study

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Soil occupies the pedosphere, one of Earth's spheres that the geosciences use to organize the Earth conceptually. This is the conceptual perspective of pedology and edaphology, the two main historical 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,[4] more integrated, less soil-centric concepts are also valuable. Many concepts essential to understanding soil come from or have been renewed by individuals not identifiable strictly as soil scientists, like biologists[5] or philosophers.[6] This highlights the interdisciplinary nature of soil concepts.[7]

Research

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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,[8][9] greenhouse gases,[10] and carbon sequestration.[11] Interest in maintaining the planet's biodiversity and in exploring past cultures has also stimulated renewed interest in achieving a more refined understanding of soil.[12][13]

Mapping

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Main article: Soil survey

Soil mapping is the process of classifying soil types and properties in a given area and geo-encoding the information. Along the second half of the 20th century soil mapping was currently achieved by field survey and reporting contours of soil types on geographic maps at varying scales according to countries and purposes. More recently digital soil mapping approaches have been developed in various countries for quantifying soils in space and time using remote sensing data.[14][15]

Classification

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Main article: Soil classification
File:Global soils map USDA.jpg
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.[16] 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.[17]

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., color, texture, landscape position), performance (e.g., production capability, flooding), and accompanying vegetation.[18] A vernacular distinction familiar to many is classifying texture as heavy (clayish) or light (sandy). Light soils with higher sand content and better structure take less effort to turn and cultivate than finer-textured soils but are more susceptible to erosion and thus to losses of production capacity.[19] Light (sandy) soils do not necessarily weigh less than heavy (clay) soils on an air dry basis (i.e. they have similar bulk density), nor do they have more porosity, but they are less sensitive to cattle trampling because they are more resistant to compaction.[20]

History

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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.[21]

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, working on the origins of soil before Dokuchaev was born.[22] However, Dokuchaev's work was more extensive and is considered to be more significant to modern soil theory than Fallou's.[23]

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-forming factors (climate, vegetation, country, relief and age). According to him, soil should be called the "daily" or outward horizon of rocks regardless of the type. Soils are changed naturally by the common effect of water, air and various kinds of living and dead organisms.[24]

A 1914 encyclopedic definition: "the different forms of earth on the surface of the rocks, formed by the breaking down or weathering of rocks".[25] 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.[26] A corollary concept is that soil without a living component is simply a part of Earth's outer layer, a regolith.[27]

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 material on the surface of the Earth's moon[28] and Mars,[29] a usage acceptable within only a portion of the scientific community.[30] 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".[31]

Areas of practice

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Academically, soil scientists tend to be drawn to one of five areas of specialization: Soil biology, pedology, edaphology, physics, or 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, with The Critical Zone concept providing a natural framework for cross-disciplinary fundamental research on soil, rock, air, water, and biotic resources at the Earth's surface.[32] Soil science professionals commonly stay current in soil chemistry, soil physics, soil biology, pedology, and applied soil science in related disciplines. However, the emergence and development of new sub-disciplines, more related to other fields of knowledge, such as biology and physics, than to the original geological framework, contributed to declining investments in research and teaching of soil science at the turn of the 21th century.[33]

One exciting effort drawing in soil scientists in the U.S. as of 2004 is the Illinois 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.[34] 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 Peace Prize laureate Norman Borlaug, the father of the Green Revolution, and World Food Prize winner Pedro Sanchez, two renowned proponents of biotechnology-based agriculture for solving the hungry problem in the tropics.[35][36]

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.[37] 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.[38] The landscape functions that soil scientists are called upon to address in the field seem to fall roughly into six areas:

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

Fields of application in soil science

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Depression storage capacity

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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.[39] 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 flooding and soil erosion. The study of land's depression storage capacity is important in the fields of geology, ecology, and especially hydrology.

See also

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References

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  1. ↑ Jackson, Julia A. (1997). Glossary of geology (4th ed.). Alexandria, Virginia: American Geological Institute. p. 604. ISBN 978-0922152346. Retrieved 28 April 2026.
  2. ↑ Rodrigo-Comino, Jesús; López-Vicente, Manuel; Kumar, Vinod; Rodríguez-Seijo, Andrés; Valkó, Orsolya; Rojas, Claudia; Pourghasemi, Hamid Reza; Salvati, Luca; Bakr, Noura; Vaudour, Emmanuelle; Brevik, Eric C.; Radziemska, Maja; Pulido, Manuel; Di Prima, Simone; Dondini, Marta; De Vries, Wim; Santos, Erika S.; Mendonça-Santos, Maria de Lourdes; Yu, Yang; Panagos, Panos (1 December 2020). "Soil science challenges in a new era: a transdisciplinary overview of relevant topics". Air, Soil and Water Research. 13: 1–17. doi:10.1177/11786221209774.
  3. ↑ Janzen, Henry H.; Fixen, Paul E.; Franzluebbers, Alan J.; Hattey, Jeffory; Izaurralde, Roberto C.; Ketterings, Quirine M.; Lobb, David A.; Schlesinger, William H. (January 2011). "Global prospects rooted in soil science". Soil Science Society of America Journal. 75 (1): 1–8. Bibcode:2011SSASJ..75....1J. doi:10.2136/sssaj2009.0216. Retrieved 28 April 2026.
  4. ↑ Huggett, Richard (23 August 2024). "Earth's spheres: conceptual and definitional debates". Progress in Physical Geography, Earth and Environment. 48 (5–6): 651–70. doi:10.1177/03091333241275465.
  5. ↑ Ponge, Jean-François (August 2022). "Humus: dark side of life or intractable "aether"?". Pedosphere. 32 (4): 660–4. doi:10.1016/S1002-0160(21)60013-9. Retrieved 28 April 2026.
  6. ↑ Sigl, Lisa; Falkenberg, Ruth; Fochler, Maximilian (February 2023). "Changing articulations of relevance in soil science: diversity and (potential) synergy of epistemic commitments in a scientific discipline". Studies in History and Philosophy of Science. 97 (1): 79–90. doi:10.1016/j.shpsa.2022.12.004.
  7. ↑ Brevik, Eric C.; Cerdà, Artemi; Mataix-Solera, Jorge; Pereg, Lily; Quinton, John L.; Six, Johan; Van Osst, Kristof (16 January 2015). "The interdisciplinary nature of soil". Soil (journal). 1 (1): 117–29. doi:10.5194/soil-1-117-2015.
  8. ↑ 8.0 8.1 Ochoa-Hueso, Raúl; Delgado-Baquerizo, Manuel; King, Paul Tuan An; Benham, Merryn; Arca, Valentina; Power, Sally A. (February 2019). "Ecosystem type and resource quality are more important than global change drivers in regulating early stages of litter decomposition". Soil Biology and Biochemistry. 129: 144–52. Bibcode:2019SBiBi.129..144O. doi:10.1016/j.soilbio.2018.11.009. hdl:10261/336676. S2CID 92606851. Retrieved 28 April 2026.
  9. ↑ Pielke, Roger (19 December 2005). "Is soil an important component of the climate system?". pielkeclimatesci.wordpress.com. Archived from the original on 8 September 2006. Retrieved 28 April 2026.
  10. ↑ Li, Changsheng (17 December 2010). "Quantifying greenhouse gas emissions from soils: scientific basis and modeling approach". Soil Science and Plant Nutrition. 53 (4): 344–52. doi:10.1111/j.1747-0765.2007.00133.x. Retrieved 28 April 2026.
  11. ↑ Lal, Rattan; Negassa, Wakene; Lorenz, Klaus (August 2015). "Carbon sequestration in soil". Current Opinion in Environmental Sustainability. 15: 79–86. doi:10.1016/j.cosust.2015.09.002. Retrieved 28 April 2026.
  12. ↑ Robinson, Jake M.; Liddicoat, Craig; Muñoz-Rojas, Miriam; Breed, Martin F. (6 May 2024). "Restoring soil biodiversity". Current Biology. 34 (9): 393–8. doi:10.1016/j.cub.2024.02.035.
  13. ↑ Salisbury, Roderick B. (5 March 2012). "Engaging with soil, past and present". Journal of Material Culture. 17 (1): 23–41. doi:10.1177/1359183511432990. Retrieved 28 April 2026.
  14. ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
  15. ↑ Behrens, Thorsten; Scholten, Thomas (June 2006). "Digital soil mapping in Germany: a review". Journal of Plant Nutrition and Soil Science. 169 (3): 434–43. doi:10.1002/jpln.200521962. Retrieved 28 April 2026.
  16. ↑ 16.0 16.1 IUSS Working Group WRB (24 September 2024). "World Reference Base for Soil Resources" (PDF) (4th ed.). Vienna, Austria: International Union of Soil Sciences. Retrieved 29 April 2026.
  17. ↑ Bryan, Kirk; Albritton, Claude C. Jr (August 1943). "Soil phenomena as evidence of climatic changes" (PDF). American Journal of Science. 241 (8): 469–90. Retrieved 29 April 2026.
  18. ↑ "Vernacular systems". Oregon State University. Archived from the original on 6 March 2007. Retrieved 29 April 2026.
  19. ↑ Donagemma, Guilherme Kangussu; de Freitas, Pedro Luiz; Balieiro, Fabiano de Carvalho; Fontana, Ademir; Spera, Silvio Túlio; Lumbreras, José Francisco; Viana, João Herbert Moreira; de Araújo Filho, José Coelho; dos Santos, Flávia Cristina; de Albuquerque, Manoel Ricardo; Macedo, Manuel Cláudio Motta; Teixeira, Paulo Cesar; Amaral, André Julio; Bortolon, Elisandra; Bortolon, Leandro (September 2016). "Characterization, agricultural potential, and perspectives for the management of light soils in Brazil". Pesquisa Agropecuária Brasileira. 51 (9): 1003–20. doi:10.1590/S0100-204X2016000900001.
  20. ↑ Van Haveren, Bruce P. (September 1983). "Soil bulk density as influenced by grazing intensity and soil type on a shortgrass prairie site" (PDF). Journal of Range Management. 36 (5): 586–8. Retrieved 29 April 2026.
  21. ↑ Krasilnikov, Pavel; Ibáñez Martí, Juan José; Arnold, Richard; Shoba, Serghei (2009). A Handbook of soil terminology, correlation and classification. London, United Kingdom: Earthscan. p. 340. ISBN 978-1844076833. Retrieved 30 April 2026.
  22. ↑ Feller, Christian; Aeschlimann, Jean-Paul; Frossard, Emmanuel (December 2022). "The contribution of Friedrich Albert Fallou to modern soil science". Journal of Plant Nutrition and Soil Science. 185 (6): 766–72. doi:10.1002/jpln.202200306.
  23. ↑ Brevik, Eric C.; Hartemink, Alfred E. (15 October 2010). "Early soil knowledge and the birth and development of soil science". Catena. 83 (1): 23–33. Retrieved 30 April 2026.
  24. ↑ Krasil'nikov, Nikolai Aleksandrovich (1958). Soil microorganisms and higher plants, translated in Israel by Y. Halperin (PDF). Moscow, Russia: Academy of Sciences of the USSR. Archived from the original on 20 November 2004. Retrieved 30 April 2026.
  25. ↑ Wikisource:The New Student's Reference Work/4-0310
  26. ↑ Buol, Stanley W.; Southard, Randal J.; Graham, Robert C.; McDaniel, Paul A. (2011). Soil genesis and classification (6th ed.). Hoboken, New Jersey: Wiley-Blackwell. p. 8. ISBN 978-0813807690. Retrieved 30 April 2026.
  27. ↑ Johnson, Donald L.; Domier, Jane E. J.; Johnson, Dana N. (2005). "Reflections on the nature of soil and its biomantle". Annals of the Association of American Geographers. 95 (1): 11–31. doi:10.1111/j.1467-8306.2005.00448.x. Retrieved 30 April 2026.
  28. ↑ Slyuta, Evgeny N. (2014). "Physical and mechanical properties of the lunar soil (a review)". Solar System Research. 48 (5): 330–53. doi:10.1134/S0038094614050050. Retrieved 30 April 2026.
  29. ↑ Banin, Amos (5 August 2005). "The enigma of the Martian soil". Science. 309 (5736): 888–90. doi:10.1126/science.1112794. Retrieved 30 April 2026.
  30. ↑ Certini, Giacomo; Scalenghe, Riccardo; Amundson, Ronald (December 2009). "A view of extraterrestrial soils". European Journal of Soil Science. 60 (6): 1078–92. doi:10.1111/j.1365-2389.2009.01173.x. Retrieved 30 April 2026.
  31. ↑ Nikiforoff, Constantin C. (23 January 1959). "Reappraisal of the soil: pedogenesis consists of transactions in matter and energy between the soil and its surroundings". Science. 129 (3343): 186–96. Bibcode:1959Sci...129..186N. doi:10.1126/science.129.3343.186. PMID 17808687. Retrieved 4 May 2026.
  32. ↑ Wilding, Larry P.; Lin, Henry (April 2006). "Advancing the frontiers of soil science towards a geoscience". Geoderma. 131 (3–4): 257–74. doi:10.1016/j.geoderma.2005.03.028. Retrieved 4 May 2026.
  33. ↑ Mermut, Ahmet R.; Eswaran, Hari (May 2001). "Some major developments in soil science since the mid-1960s". Geoderma. 100 (3–4): 403–26. doi:10.1016/S0016-7061(01)00030-1. Retrieved 4 May 2026.
  34. ↑ Walter, Gerry; Wander, Michelle; Bollero, Germán (June 1997). "A farmer-centered approach to developing information for soil resource management: the Illinois Soil Quality Initiative". American Journal of Alternative Agriculture. 12 (2): 64–72. doi:10.1017/S0889189300007268. Retrieved 4 May 2026.
  35. ↑ Sojka, Robert E.; Upchurch, Dan R.; Borlaug, Norman E. (2003). "Quality soil management or soil quality management: performance versus semantics" (PDF). Advances in Agronomy. 79: 1–68. doi:10.1016/S0065-2113(02)79001-9. Retrieved 4 May 2026.
  36. ↑ Sanchez, Pedro A.; Palm, Cheryl A.; Buol, Stanly W. (June 2003). "Fertility capability soil classification: a tool to help assess soil quality in the tropics". Geoderma. 114 (3–4): 157–85. doi:10.1016/S0016-7061(03)00040-5. Retrieved 4 May 2026.
  37. ↑ Brevik, Eric C.; Hartemink, Alfred E. (July–August 2013). "Soil maps of the United States of America". Soil Science Society of America Journal. 77 (4): 1117–32. doi:10.2136/sssaj2012.0390. Retrieved 4 May 2026.
  38. ↑ Bui, Elisabeth N.; Loughhead, Andrew; Corner, Robert (7 April 1999). "Extracting soil-landscape rules from previous soil surveys". Australian Journal of Soil Research. 37 (3): 495–508. doi:10.1071/S98047. Retrieved 4 May 2026.
  39. ↑ Hansen, Bjarne; Schjønning, Per; Sibbesen, Erik (September 1999). "Roughness indices for estimation of depression storage capacity of tilled soil surfaces". Soil and Tillage Research. 52 (1–2): 103–11. doi:10.1016/S0167-1987(99)00061-6. Retrieved 4 May 2026.

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