- LAST REVIEWED: 24 March 2021
- LAST MODIFIED: 25 November 2014
- DOI: 10.1093/obo/9780199363445-0008
- LAST REVIEWED: 24 March 2021
- LAST MODIFIED: 25 November 2014
- DOI: 10.1093/obo/9780199363445-0008
Soils are made up of inorganic and organic compounds inclusive of living organisms. Soil salinization is the accumulation of water-soluble salts within soil layers above a certain level that adversely affects crop production, environmental health, and economic welfare. Soil salinity is described and characterized in terms of the concentration and composition of the soluble salts. Even though soluble salts are inherent in all soils, there are many processes that can contribute to the build-up of salts in a given soil layer. Weathering of soil minerals, salts added through rain, agronomic practices such as fertilizer and pesticide application, saline groundwater intrusion with water table fluctuations, irrigation with saline water sourced from bore, recycled or waste waters, dumping of industrial and municipal wastes into soils, and other soil conditions leading to reduced leaching of salts from the soil layer—all can lead to soil salinization. Seawater intrusion onto land when sea levels increase can deposit a large amount of salts in soils of coastal lands. The particular processes contributing salt, combined with the influence of other climatic, hydrological, and landscape features and the effects of human activities, farming practices, and plant interactions, determine where salinization occurs. Worldwide, more than 800 million hectares of land are estimated to be salt-affected, covering a range of soils defined as saline, saline-sodic and sodic in every climatic zone in every continent except Antarctica. All soil types with diverse morphological, physical, chemical, and biological properties may be affected by salinization. Generally, salt-affected soils are predominant in arid and semi-arid regions.
Processes of Soil Salinization
Soil salinization is normally classified as “primary” and “secondary” salinity, based on whether salt accumulates by natural phenomena or as a consequence of the management of natural resources. There are three major types of salinity based on soil and groundwater processes found all over the world. They are: (1) groundwater-associated salinity, or fluctuations in groundwater (usually saline) leading to water and salt discharge on soil surface layers; (2) non-groundwater-associated salinity, or poor hydraulic properties of soil layers (commonly found in sodic soils) resulting in reduced leaching; and (3) irrigation-associated salinity, where salts introduced by irrigation water are stored in soil layers because of insufficient leaching. During these processes, the secondary salinization is usually accelerated or enhanced by several human activities. With the introduction of agriculture and clearance of perennial native vegetation, the equilibrium levels of the water tables change. In low-lying regions, where water tables are shallower, more unused water by crops and pastures, with salt, leaks from the upper soil layers and raises the levels of groundwater. As the groundwater approaches soil surface, salt accumulates, aided by evaporation. In coastal aquifers, the salt water from the sea flows inland into freshwater aquifers, causing saltwater intrusion, a result of the density difference caused by salinity levels between seawater and freshwater, as defined by the Ghyben-Herzberg principle. This process is enhanced by the extraction of fresh groundwater. In irrigated regions, the quantity and quality of salt in irrigation water leads to the accumulation of salts when drainage conditions do not meet leaching requirements. Salt deposition from wind-blown materials from desiccated lakes and seepage from urban infrastructure also lead to soil salinization.
Artzy, M., and D. Hillel. 1988. A defense of the theory of progressive soil salinization in ancient southern Mesopotamia. Geoarcheology 3:235–238.
Artzy and Hillel 1988 is a paper that gives an explanation of the fundamental processes of soil salinization and degradation induced by irrigation of poorly drained river valleys in arid regions, and it explains why these processes were practically uncontrollable under the circumstances of ancient southern Mesopotamia.
Beresford, Q., H. Bekle, H. Phillips, and J. Mulcock. 2001. The salinity crisis: Landscapes, communities and politics. Crawley: Univ. of Western Australia Press.
Beresford, et al. 2001 is a paper that deals with the secondary salinization and the impact of stream salinization in relation to landscapes in Western Australia and the role of communities and politics.
Ghassemi, F., A. J. Jakeman, and H. A. Nix. 1995. Salinization of land and water resources: Human causes, extent, management and case studies. Sydney: Univ. of New South Wales Press Ltd.
Ghassemi, et al. 1995 is a book that reviews the global and regional extent of salinization of land and water resources. The authors describe salinity problems in thirteen selected countries, including Argentina, Australia, China, Egypt, India, Iran, Pakistan, South Africa, Thailand, and the United States, as well as processes of salinization in land and water resources and management strategies.
Hillel, D. 2005. Soil salinity: Historical and contemporary perspectives. Proceedings of the International Salinity Forum, Riverside, California, April 25–27, 2005, 235–240. Riverside, CA: Water Science and Policy Center.
Hillel 2005 is a paper that discusses historical and contemporary perspectives on soil salinity. This paper is useful to understand the general nature of salinization through generations.
Jacobsen, T., and R. M. Adams. 1958. Salt and silt in ancient Mesopotamian agriculture. Science 128:1252.
Jacobsen and Adams 1958 is a short paper which gives an account of salinization problems in an ancient civilization. Shows that the problem of salinity is not new, and how salinization can destroy an entire civilization.
Rengasamy, P. 2006. World salinization with emphasis on Australia. Journal of Experimental Botany 57:1017–1023.
Rengasamy 2006 is a paper that reviews the different types of salinity found globally, and specifically distinguishes the transient salinity not associated with groundwater. This paper also examines the subsoil constraints associated with salinization of Australian soils and the soil processes that dictate the edaphic environment important for root functions.
Salama, R. B., C. J. Otto, and R. W. Fitzpatrick. 1999. Contributions of groundwater conditions to soil and water salinization. Hydrogeology Journal 7:46–64.
Salama, et al. 1999 is a paper that explains salinization by two main chemical models developed by the authors: weathering and deposition. Provides details on case studies at a small catchment scale in South and Western Australia. The authors compare the situations in Australia, the United States, and Sudan.
Schofield, R., D. S. G. Thomas, and M. J. Kirkby. 2001. Causal processes of soil salinization in Tunisia, Spain and Hungary. Land Degradation & Development 12:163–181.
Schofield, et al. 2001 is a paper that presents the results from the study of three contrasting salt-affected landscapes. Irrigation-oriented salinity in Spain, the natural occurrence of salt-affected soil in Hungary, and the catenary relationship to salinity in Tunisia are discussed to demonstrate various causal processes of soil salinization.
Vengosh, A. 2003. Salinization and saline environments. Treatise on Geochemistry 9:333–365.
Vengosh 2003 is an essay which recognizes that salinization is a global environmental phenomenon affecting many aspects of human life. The author explains in detail river salinization, lake salinization, groundwater salinization, salinization of dryland environment, and anthropogenic salinization. He also elucidates the sources of salinity.
Users without a subscription are not able to see the full content on this page. Please subscribe or login.
- Acid Deposition
- Agricultural Land Abandonment
- Agrochemical Pollutants
- Agroforestry Systems
- Agroforestry: The North American Perspective
- Applied Fluvial Ecohydraulic
- Arctic Environments
- Arid Environments
- Arsenic Contamination in South and Southeast Asia
- Beavers as Agents of Landscape Change
- Berry, Wendell
- Burroughs, John
- Bush Encroachment
- Carbon Dynamics
- Carbon Pricing and Emissions Trading
- Carson, Rachel
- Case Studies in Groundwater Contaminant Fate and Transport
- Citizen Science
- Climate Change and Conflict in Northern Africa
- Common Pool Resources
- Contaminant Dispersal in the Environment
- Coral Reefs and Coral Bleaching
- Deforestation in Brazilian Amazonia
- Desert Dust in the Atmosphere
- Determinism, Environmental
- Digital Earth
- Ecological Integrity
- Economic Valuation Methods for Non-market Goods or Service...
- Economics, Environmental
- Economics of International Environmental Agreements
- Economics of Water Management
- Effects of Land Use
- Endocrine Disruptors
- Endocrinology, Environmental
- Engineering, Environmental
- Environmental Assessment
- Environmental Flows
- Environmental Health
- Environmental Law
- Environmental Sociology
- Ethics, Animal
- Ethics, Environmental
- European Union and Environmental Policy, The
- Extreme Weather and Climate
- Feedback Dynamics
- Fisheries, Economics of
- Forensics, Environmental
- Forest Transition
- Geodiversity and Geoconservation
- Geology, Environmental
- Global Phosphorus Dynamics
- Hazardous Waste
- Henry David Thoreau
- Historical Changes in European Rivers
- Historical Land Uses and Their Changes in the European Alp...
- Historical Range of Variability
- History, Environmental
- Human Impact on Historical Fluvial Sediment Dynamics in Eu...
- Humid Tropical Environments
- Hydraulic Fracturing
- India and the Environment
- Industrial Contamination, Case Studies in
- Integrated Assessment Models (IAMs) for Climate Change
- International Land Grabbing
- Karst Caves
- Key Figures: North American Environmental Scientist Activi...
- Lakes: A Guide to the Scientific Literature
- Land Use, Land Cover and Land Management Change
- Landscape Architecture and Environmental Planning
- Large Wood in Rivers
- Legacy Effects
- Lidar in Environmental Science, Use of
- Management, Australia's Environment
- Marine Mining
- Marine Protected Areas
- Mediterranean Environments
- Mountain Environments
- Muir, John
- Multiple Stable States and Regime Shifts
- Murray-Darling Basin Plan: Case Study in Market-Based Appr...
- Natural Fluvial Ecohydraulics
- Nitrogen Cycle, Human Manipulation of the Global
- Non-Renewable Resource Depletion and Use
- Olmsted, Frederick Law
- Periglacial Environments
- Physics, Environmental
- Psychology, Environmental
- Remote Sensing
- Riparian Zone
- River Pollution
- Rivers and Their Cultural Values: Assessing Cultural Water...
- Rivers, Effects of Dams on
- Rivers, Restoration of Physical Integrity of
- Sea Level Rise
- Secondary Forests in Tropical Environments
- Security, Energy
- Security, Environmental
- Security, Water
- Sediment Budgets and Sediment Delivery Ratios in River Sys...
- Sediment Regime and River Morphodynamics
- Semiarid Environments
- Soil Salinization
- Soils as an Environmental System
- Spatial Statistics
- Stream Mitigation Banking
- Sustainable Finance
- Sustainable Forestry, Economics of
- Technological and Hybrid Disasters
- The Key Role of Energy in Economic Growth
- Thresholds and Tipping Points
- Treaties, Environmental
- Tropical Southeast Asia
- Use of GIS in Environmental Science
- Water Availability
- Water Quality in Freshwater Bodies
- Water Quality Metrics
- Water Resources and Climate Change
- Water, Virtual
- White, Gilbert Fowler
- Wildfire as a Catalyst
- Zone, Critical