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Soil salinity

From Wikipedia, the free encyclopedia
(Redirected from Sodic soil)
Visibly salt-affected soils on rangeland in Colorado. Salts dissolved from the soil accumulate at the soil surface and are deposited on the ground and at the base of the fence post.
Saline incrustation in a PVC irrigation pipe from Brazil

Soil salinity is the salt content in the soil; the process of increasing the salt content is known as salinization (also called salination in American English).[1] Salts occur naturally within soils and water. Salinization can be caused by natural processes such as mineral weathering[2] or by the gradual withdrawal of an ocean.[3] It can also come about through artificial processes such as irrigation[4] and road salt.[5]

Natural occurrence

[edit]

Salts are a natural component in soils and water bodies. The ions responsible for salinization are: Na+, K+, Ca2+, Mg2+ and Cl−.[6]

Over long periods of time, as soil minerals weather and release salts,[7] these salts are flushed or leached out of the soil by drainage water in areas with sufficient precipitation[8] or under irrigation,[9] or may rise through capillarity and accumulate near the surface under intense evaporation during drought periods.[10] In addition to mineral weathering, salts are also deposited via dust[11] and precipitation.[12] Salts may accumulate in dry regions, leading to naturally saline soils.[13] This is the case, for example, in large parts of Australia.

Human practices can increase the salinity of soils by the addition of salts in irrigation water.[14] Proper irrigation management can prevent salt accumulation by providing adequate drainage water (e.g. rainwater) to leach added salts from the soil.[15] Disrupting drainage patterns that provide leaching can also result in salt accumulations. An example of this occurred in Egypt in 1970 when the Aswan High Dam was built. The change in the level of ground water before the construction had enabled soil erosion, which led to high concentration of salts in the water table. After the construction, the continuous high level of the water table led to the salinization of arable land.[16] The increase in aridity caused by human-induced global warming also contributes to the salinization of waterlogged soils.[17]

Sodic soils

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When the Na+ (sodium) predominates, soils can become sodic. The pH of sodic soils may be acidic, neutral, or alkaline.[18]

Sodic soils present particular challenges because they tend to have very poor structure which limits or prevents water infiltration and drainage.[19] They tend to accumulate certain elements like boron and molybdenum in the root zone at levels that may be toxic for plants.[20] The most common compound used for reclamation of sodic soil is gypsum,[21] and some organisms that are tolerant to salt and ion toxicity (e.g. halophytes, halophilic rhizobacteria) may offer strategies for improvement.[22]

The term "sodic soil" is sometimes used imprecisely in scholarship. It's been used interchangeably with the term alkali soil, which is used in two meanings: 1) a soil with a pH greater than 8.2, 2) a soil with an exchangeable sodium content above 15% of cation-exchange capacity. The term "alkali soil" is often, but not always, used for soils that meet both of these characteristics.[23]

Dry land salinity

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Salinity in drylands can occur when the water table is between two and three metres from the surface for clayey soils but for sandy soils it may be less than a metre.[24] The salts from the groundwater are raised by capillary action to the surface of the soil.[25] This occurs when groundwater is saline (which is true in many areas), and is favored by land use practices allowing more rainwater to enter the aquifer than it could accommodate. For example, the clearing of trees for agriculture is a major reason for dryland salinity in some areas, since deep rooting of trees has been replaced by shallow rooting of annual crops.[26]

Salinity due to irrigation

[edit]
Rain or irrigation, in the absence of leaching, can bring salts to the surface by capillary action.

Salinity from irrigation can occur over time wherever irrigation occurs, since almost all water (even natural rainfall) contains some dissolved salts.[27] When the plants use the water, the salts are left behind in the root zone (rhizosphere) and eventually begin to accumulate.[28] This water in excess of plant needs is called the leaching fraction. Salinization from irrigation water is also greatly increased by poor drainage and use of saline water for irrigating agricultural crops.[29]

Salinity in urban areas often results from the combination of irrigation, now common in gardens and recreation areas, often using salt-laden reclaimed water, and groundwater processes.[30]

Consequences of soil salinity

[edit]

The consequences of salinity are

Salinity is an important land degradation problem. Soil salinity can be reduced by leaching soluble salts out of soil with excess irrigation water. Soil salinity control involves watertable control and flushing in combination with tile drainage or another form of subsurface drainage.[36][37] A comprehensive treatment of soil salinity is available from the United Nations Food and Agriculture Organization.[38]

The presence of soluble salts in soils can significantly influence their engineering properties, particularly under varying moisture conditions. Studies have shown that long-term soaking can lead to dissolution and redistribution of salts in clayey and gypsiferous soils, resulting in changes in soil structure and a reduction in strength and stiffness.[39]

Research on gypsiferous soils has further demonstrated that moisture variation and soaking conditions can significantly affect mechanical performance due to gypsum dissolution and changes in internal soil structure.[40]

Earlier studies have also shown that compaction conditions interact with salinity effects, where increased compaction improves initial strength, but long-term exposure to moisture may still result in degradation due to dissolution of soluble salts in gypsiferous soils.[41]

Salt tolerance of crops

[edit]

High levels of soil salinity can be tolerated if salt-tolerant plants are grown. Sensitive crops lose their vigor already in slightly saline soils, most crops are negatively affected by (moderately) saline soils, and only salinity-resistant crops thrive in severely saline soils. The University of Wyoming[42] and the Government of Alberta[43] report data on the salt tolerance of plants.

Field data in irrigated lands, under farmers' conditions, are scarce, especially in developing countries. However, some on-farm surveys have been made in Egypt,[44] India,[45] and Pakistan.[46] Some examples are shown in the following gallery, with crops arranged from sensitive to very tolerant.[47][48]

Calcium has been found to have a positive effect in combating salinity in soils. It has been shown to ameliorate the negative effects that salinity has such as reduced water usage of plants.[49]

Soil salinity activates genes associated with stress conditions for plants.[50] These genes initiate the production of plant stress enzymes such as superoxide dismutase, L-ascorbate oxidase, and Delta 1 DNA polymerase. Limiting this process can be achieved by administering exogenous glutamine to plants. The decrease in the level of expression of genes responsible for the synthesis of superoxide dismutase increases with the increase in glutamine concentration.[50]

Regions affected

[edit]

From the FAO/UNESCO Soil Map of the World the following salinised areas can be derived.[51]

RegionArea (106 ha)
Africa69.5
Near and Middle East53.1
Asia and Far East19.5
Latin America59.4
Australia84.7
North America16.0
Europe20.7

See also

[edit]

References

[edit]
  1. ↑ "Salinization: a global challenge". www.salineagricultureworldwide.com. Retrieved 24 July 2026.
  2. ↑ Kaushal, Sujay S.; Likens, Gene E.; Pace, Michael L.; Grese, Melissa (8 January 2018). "Freshwater salinization syndrome on a continental scale". PNAS. 115 (4): E574–E583. doi:10.1073/pnas.1711234115. PMC 5789913.
  3. ↑ Adams, Kyra H.; Reager, John Thomas; Buzzanga, Brett A.; David, Cédric H.; Sawyer, Audrey H.; Hamlington, Benjamin D. (28 November 2024). "Climate-induced saltwater intrusion in 2100: recharge-driven severity, sea level-driven prevalence". Geophysical Research Letters. 51 (22) e2024GL110359. doi:10.1029/2024GL110359.
  4. ↑ Saysel, Ali Kerem; Barlas, Yaman (30 April 2001). "A dynamic model of salinization on irrigated lands". Ecological Modelling. 139 (2–3): 177–199. doi:10.1016/S0304-3800(01)00242-3. Retrieved 24 July 2026.
  5. ↑ Chernousenko, G. I.; Yamnova, Irina A.; Skripnikova, M. I. (2003). "Anthropogenic salinization of soils in Moscow". Eurasian Soil Science. 36 (1): 97–105. ISSN 1064-2293. Retrieved 24 July 2026.
  6. ↑ Liu, Zhenlin; Gao, Maosheng; Sun, Qiming; Hou, Guohua; Zhao, Yinxin (15 August 2023). "Formation and evolution of soil salinization based on multivariate statistical methods in Ningxia Plain, China". Frontiers in Earth Science. 11 (1) 1186779. doi:10.3389/feart.2023.1186779.
  7. ↑ Rhoades, J. D.; Krueger, D. B.; Reed, M. J. (September–October 1968). "The effect of soil-mineral weathering on the sodium hazard of irrigation waters". Soil Science Society of America Journal. 32 (5): 643–647. doi:10.2136/sssaj1968.03615995003200050020x. Retrieved 24 July 2026.
  8. ↑ Carroll, Dorothy (1962). Rainwater as a chemical agent of geologic processes: a review (PDF). Washington, District of Columbia: United States Government Printing Office. Retrieved 24 July 2026.
  9. ↑ Zeng, WenZhi; Xu, Chi; Wu, JingWei; Huang, JieSheng (1 June 2013). "Soil salt leaching under different irrigation regimes: HYDRUS-1D modelling and analysis". Journal of Arid Land. 6 (1): 44–58. doi:10.1007/s40333-013-0176-9. ISSN 2194-7783. Retrieved 24 July 2026.
  10. ↑ Li, Huiying; Wang, Shuo (28 November 2025). "Growing risk of soil salinization linked to soil droughts in a changing climate". Geophysical Research Letters. 52 (22) e2025GL119349. doi:10.1029/2025GL119349.
  11. ↑ Liu, Dongwei; Abuduwaili, Jilili; Lei, Jiaqiang; Wu, Guangyang (21 September 2010). "Deposition rate and chemical composition of the aeolian dust from a bare saline playa, Ebinur Lake, Xinjiang, China". Water, Air, & Soil Pollution. 218 (1): 175–184. doi:10.1007/s11270-010-0633-4. Retrieved 24 July 2026.
  12. ↑ Möller, Detlev (July 1990). "The Na/CL ratio in rainwater and the seasalt chloride cycle". Tellus B. 42 (3): 254–262. doi:10.1034/j.1600-0889.1990.t01-1-00004.x. Retrieved 24 July 2026.
  13. ↑ Breckle, Siegmar-Walter (2002). "Salinity, halophytes and salt affected natural ecosystems". In Läuchli, André; Lüttge, Ulrich (eds.). Salinity: environment, plants, molecules. Dordrecht, The Netherlands: Springer Science+Business Media. pp. 53–77. doi:10.1007/0-306-48155-3_3. ISBN 978-0-306-48155-0. Retrieved 27 July 2026.
  14. ↑ Fipps, Guy. "Irrigation water quality standards and salinity management". oaktrust.library.tamu.edu. Retrieved 27 July 2026.
  15. ↑ Minhas, Paramjit S. (March 1996). "Saline water management for irrigation in India". Agricultural Water Management. 30 (1): 1–24. doi:10.1016/0378-3774(95)01211-7. ISSN 1873-2283. Retrieved 27 July 2026.
  16. ↑ Omran, El-Sayed Ewis (2018). "Land and groundwater resources in the Egypt's Nile Valley, delta, and its fringes". In Negm, Abdelazim M. (ed.). Groundwater in the Nile delta. The Handbook of Environmental Chemistry. Vol. 73. Cham, Switzerland: Springer Science+Business Media. pp. 45–103. doi:10.1007/698_2017_64. ISBN 978-3-319-94283-4. ISSN 1616-864X. Retrieved 27 July 2026.
  17. ↑ Okur, Bülent; Örçen, Nesrin (2020). "Soil salinization and climate change". In Prasad, Majeti Narasimha Vara; Pietrzykowski, Marcin (eds.). Climate change and soil interactions. Amsterdam, The Netherlands: Elsevier. pp. 331–350. doi:10.1016/B978-0-12-818032-7.00012-6. ISBN 978-0-12-818032-7. Retrieved 27 July 2026.
  18. ↑ Naidu, Ravi; Rengasamy, Pichu (December 1993). "Ion interactions and constraints to plant nutrition in Australian sodic soils". Australian Journal of Soil Research. 31 (6): 801–819. doi:10.1071/SR9930801. Retrieved 24 July 2026.
  19. ↑ So, H. B.; Aylmore, Lag (December 1993). "How do sodic soils behave: the effects of sodicity on soil physical behavior". Australian Journal of Soil Research. 31 (6): 761–777. doi:10.1071/SR9930761. Retrieved 24 July 2026.
  20. ↑ "Sodic soils and their management". www.fao.org. Retrieved 27 July 2026.
  21. ↑ Oster, James D.; Frenkel, H. (January–February 1980). "The chemistry of the reclamation of sodic soils with gypsum and lime". Soil Science Society of America Journal. 44 (1): 41–45. doi:10.2136/sssaj1980.03615995004400010010x. Retrieved 28 July 2026.
  22. ↑ Sree, S. Soniya; Al-zharani, Mohammed; Nasr, Fahd A.; Alneghery, Lina M.; Kumar, T. T. Ajith; Sureshkumar, B. T.; Mohamed, Jamal Moideen Muthu; Ravichandran, Mythili; Dineshkumar, R. (9 August 2025). "Innovative bio-amelioration strategies for sustainable reclamation of salt-affected agroecosystems: a review". Plant and Soil. 516 (1): 67–114. doi:10.1007/s11104-025-07749-0. Retrieved 28 July 2026.
  23. ↑ Gupta, S. K.; Gupta, I. C. (1 October 2017). Genesis and management of sodic (alkali) soils. Jodhpur, India: Scientific Publishers. ISBN 978-93-87869-64-6.
  24. ↑ McFarlane, Don J.; George, Richard J.; Barrett-Lennard, Edward G.; Gilfedder, Mat (2016). "Salinity in dryland agricultural systems: challenges and opportunities". In Farooq, Muhammad; Siddique, Kadambot H. M. (eds.). Innovations in dryland agriculture. Cham, Switzerland: Springer Nature. pp. 521–547. doi:10.1007/978-3-319-47928-6_19. ISBN 978-3-319-47928-6. Retrieved 28 July 2026.
  25. ↑ Jorenush, Mohammad Hadi; Sepaskhah, Ali Reza (30 June 2003). "Modelling capillary rise and soil salinity for shallow saline water table under irrigated and non-irrigated conditions". Agricultural Water Management. 61 (2): 125–141. doi:10.1016/S0378-3774(02)00176-2. ISSN 1873-2283. Retrieved 28 July 2026.
  26. ↑ Giménez, Raúl; Mercau, Jorge; Nosetto, Marcelo; Páez, Ricardo; Jobbágy, Esteban (15 July 2016). "The ecohydrological imprint of deforestation in the semiarid Chaco: insights from the last forest remnants of a highly cultivated landscape". Hydrological Processes. 30 (15): 2603–2616. doi:10.1002/hyp.10901. ISSN 1099-1085. Retrieved 28 July 2026.
  27. ↑ Oosterbaan, Roland J. (1989). "Effectiveness and social/environmental impacts of irrigation projects: a review" (PDF). waterlog.info. Archived (PDF) from the original on 16 February 2024. Retrieved 28 July 2026.
  28. ↑ Liu, Anqi; Qu, Zhongyi; Nachshon, Uri (1 May 2020). "On the potential impact of root system size and density on salt distribution in the root zone". Agricultural Water Management. 234 (3) 106118. doi:10.1016/j.agwat.2020.106118. ISSN 0378-3774. Retrieved 28 July 2026.
  29. ↑ Singh, Ajay (December 2018). "Salinization of agricultural lands due to poor drainage: a viewpoint". Ecological Indicators. 95 (Part 1): 127–130. doi:10.1016/j.ecolind.2018.07.037. ISSN 1872-7034. Retrieved 28 July 2026.
  30. ↑ Chen, Weiping; Lu, Sidan; Pan, Neng; Jiao, Wentao (November 2013). "Impacts of long-term reclaimed water irrigation on soil salinity accumulation in urban green land in Beijing". Water Resources Research. 49 (11): 7401–7410. doi:10.1002/wrcr.20550. Retrieved 28 July 2026.
  31. ↑ Zörb, Christian; Geilfus, Christoph-Martin; Dietz, Karl-Josef (January 2019). "Salinity and crop yield". Plant Biology. 21 (S1): 31–38. doi:10.1111/plb.12884. Retrieved 28 July 2026.
  32. ↑ Wilson, Suzanne M. (2003). "Understanding and preventing impacts of salinity on infrastructure in rural and urban landscapes" (PDF). southburnett.com. Retrieved 28 July 2026.
  33. ↑ University of Maryland (3 December 2018). "Saltier waterways are creating dangerous 'chemical cocktails'". phys.org. Archived from the original on 9 July 2023. Retrieved 28 July 2026.
  34. ↑ Pla Sentis, Ildefonso (1996). "Soil salinization and land desertification" (PDF). In Rubio, José Luis; Calvo Cases, Adolfo (eds.). Soil degradation and desertification in Mediterranean environments. Logroño, Spain: Geoforma Ediciones. pp. 105–128. ISBN 84-87779-26-3. Retrieved 28 July 2026.
  35. ↑ Sinha, Shreeja; Matsumoto, T.; Tanaka, Y.; Ishida, J.; Kojima, T.; Kumar, S. (January 2002). "Solar desalination of saline soil for afforestation in arid areas: numerical and experimental investigation". Energy Conversion and Management. 43 (1): 15–31. doi:10.1016/S0196-8904(01)00004-8. Retrieved 28 July 2026.
  36. ↑ Drainage Manual: A Guide to Integrating Plant, Soil, and Water Relationships for Drainage of Irrigated Lands, Interior Dept., Bureau of Reclamation, 1993, ISBN 978-0-16-061623-5
  37. ↑ "Free articles and software on drainage of waterlogged land and soil salinity control". Retrieved 2010-07-28.
  38. ↑ Salt-Affected Soils and their Management, FAO Soils Bulletin 39 (http://www.fao.org/docrep/x5871e/x5871e00.htm)
  39. ↑ Razouki, S. S.; Kuttah, D. K.; Jassim, N. W. (2012). "Modelling the Decrease of Total Soluble Salts of Clayey Soils during Long-term Soaking". Quarterly Journal of Engineering Geology and Hydrogeology. 45 (1): 111–118.
  40. ↑ Kuttah, D.; Sato, K. (2015). "Review on the Effect of Gypsum Content on Soil Behavior". Transportation Geotechnics. 4: 28–37.
  41. ↑ Razouki, S. S.; Kuttah, D. K.; Al-Damluji, O. A.; Nashat, I. H. (2011). "Improving Fine-Grained Gypsiferous Soil by Increased Compaction". International Journal of Pavement Engineering. 13 (1): 32–38.
  42. ↑ Alan D. Blaylock, 1994, Soil Salinity and Salt tolerance of Horticultural and Landscape Plants. University of Wyoming Archived 2010-05-08 at the Wayback Machine
  43. ↑ Government of Alberta, Salt tolerance of Plants Archived 2010-02-21 at the Wayback Machine
  44. ↑ H.J. Nijland and S. El Guindy, Crop yields, watertable depth and soil salinity in the Nile Delta, Egypt. In: Annual report 1983. International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands.
  45. ↑ D. P. Sharma, K. N. Singh and K. V. G. K. Rao (1990), Crop Production and soil salinity: evaluation of field data from India. Paper published in Proceedings of the Symposium on Land Drainage for Salinity Control in Arid and Semi-Arid Regions, February, 25th to March 2nd, 1990, Cairo, Egypt, Vol. 3, Session V, p. 373–383. On line:
  46. ↑ R.J. Oosterbaan, Crop yields, soil salinity and water table depth in Pakistan. In: Annual Report 1981, pp. 50–54. International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands, reprinted in Indus 24 (1983) 2, pp. 29–33. On line
  47. ↑ "Crop tolerance for soil salinity in farmers' fields". www.waterlog.info. Retrieved 2023-02-08.
  48. ↑ Crop Tolerance to Soil Salinity, Statistical Analysis of Data Measured in Farm Lands. In: International Journal of Agricultural Science, October 2018. On line:
  49. ↑ Kaya, C; Kirnak, H; Higgs, D; Saltali, K (2002-02-28). "Supplementary calcium enhances plant growth and fruit yield in strawberry cultivars grown at high (NaCl) salinity". Scientia Horticulturae. 93 (1): 65–74. Bibcode:2002ScHor..93...65K. doi:10.1016/S0304-4238(01)00313-2.
  50. 1 2 Ulukapi, Kamile; Nasircilar, Ayse Gul (February 2024). "The role of exogenous glutamine on germination, plant development and transcriptional expression of some stress-related genes in onion under salt stres". Folia Horticulturae. 36 (1). Polish Society of Horticultural Science: 19–34. doi:10.2478/fhort-2024-0002. S2CID 19887643.
  51. ↑ R. Brinkman, 1980. Saline and sodic soils. In: Land reclamation and water management, pp. 62–68. International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands.
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