Soil salinity - wikipedia Soil salinity 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. Soil salinity is the salt content in the soil ; the process of increasing the salt content is known as salinization. Salts occur naturally within soils and water. Salination can be caused by natural processes such as mineral weathering or by the gradual withdrawal of an ocean. It can also come about through artificial processes such as irrigation. Contents 1 Natural occurrence 2 Dry land salinity 3 Salinity due to irrigation 4 Consequences of salinity 5 Salt tolerance of crops 6 Regions affected 7 See also 8 References 9 External links Natural occurrence Salts are a natural component in soils and water. The ions responsible for salination are : Na, K, Ca, Mg and Cl. As the Na ( sodium ) predominates, soils can become sodic. Sodic soils present particular challenges because they tend to have very poor structure which limits or prevents water infiltration and drainage. Over long periods of time, as soil minerals weather and release salts, these salts are flushed or leached out of the soil by drainage water in areas with sufficient precipitation. In addition to mineral weathering, salts are also deposited via dust and precipitation. In dry regions salts may accumulate, leading to naturally saline soils. 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. Proper irrigation management can prevent salt accumulation by providing adequate drainage water to leach added salts from the soil. 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 salination of the arable land. Dry land salinity Salinity in drylands can occur when the water table is between two and three metres from the surface of the soil. The salts from the groundwater are raised by capillary action to the surface of the soil. 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. Salinity due to irrigation Rain or irrigation, in the absence of leaching, can bring salts to the surface by capillary action Main article : Environmental impacts of irrigation Salinity from irrigation can occur over time wherever irrigation occurs, since almost all water ( even natural rainfall ) contains some dissolved salts. When the plants use the water, the salts are left behind in the soil and eventually begin to accumulate. Since soil salinity makes it more difficult for plants to absorb soil moisture, these salts must be leached out of the plant root zone by applying additional water. This water in excess of plant needs is called the leaching fraction. Salination from irrigation water is also greatly increased by poor drainage and use of saline water for irrigating agricultural crops. Salinity in urban areas often results from the combination of irrigation and groundwater processes. Irrigation is also now common in cities ( gardens and recreation areas ). Consequences of salinity The consequences of salinity are detrimental effects on plant growth and yield damage to infrastructure ( roads, bricks, corrosion of pipes and cables ) reduction of water quality for users, sedimentation problems soil erosion ultimately, when crops are too strongly affected by the amounts of salts. 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. A comprehensive treatment of soil salinity is available from the United Nations Food and Agriculture Organization. Salt tolerance of crops Further information : Maas -- Hoffman model and Van Genuchten -- Gupta model 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 and the Government of Alberta report data on the salt tolerance of plants. Field data, under farmers ' conditions, in irrigated lands are scarce, especially in developing countries. However, some on farm surveys were made in Egypt, India, and Pakistan. Some examples are shown in the following gallery with crops arranged from sensitive to very tolerant.. Graphs of crop yield and soil salinity in farmers ' fields ordered by increasing salt tolerance. Fig. 1. Berseem ( clover ), cultivated in Egypt 's Nile Delta is a salt sensitive crop and tolerates an ECe value up to 2.4 dS / m whereafter yields start to decline. Fig. 2. Wheat grown in Sampla, Haryana, India is slightly sensitive tolerating an ECe value of 4.9 dS / m. Fig. 3. The field measurements in wheat fields in Gohana, Haryana, India, showed a higher tolerance level of ECe = 7.1 dS / m. ( The Egyptian wheat, not shown here, exhibited a tolerance point of 7.8 dS / m ). Fig. 4. The cotton grown in the Nile Delta can be called salt just tolerant with a critical ECe value of 8.0 dS / m. However, due to scarcity of data beyond 8 dS / m, the maximum tolerance level can not be precisely determined and may actually be higher than that. Fig. 5. Sorghum from Khairpur, Pakistan is quite tolerant, it grows well up to ECe = 10.5 dS / m Fig. 6. Cotton from Khairpur, Pakistan is very tolerant, it grows well up to ECe = 15.5 dS / m Regions affected From the FAO / UNESCO Soil Map of the World the following salinised areas can be derived. Region Area ( 10 ha ) Africa 69.5 Near and Middle East 53.1 Asia and Far East 19.5 Latin America 59.4 Australia 84.7 North America 16.0 Europe 20.7 See also Water portal Salt tolerance of crops Desalination Environmental impacts of deicing salt Water softening U.S. Salinity Laboratory Salinity in Australia References Jump up ^ from `` Soil salinity '' in WaterWiki, the on - line Knowledge and Collaboration Tool of the Community of Practice ( CoP ) on Water - and UNDP - related activities in Central and South - Eastern Europe, Caucasus and Central Asia. Jump up ^ ILRI ( 1989 ), Effectiveness and Social / Environmental Impacts of Irrigation Projects : a Review ( PDF ), In : Annual Report 1988 of the International Institute for Land Reclamation and Improvement ( ILRI ), Wageningen, The Netherlands, pp. 18 -- 34 Jump up ^ Drainage Manual : A Guide to Integrating Plant, Soil, and Water Relationships for Drainage of Irrigated Lands, Interior Dept., Bureau of Reclamation, 1993, ISBN 0 - 16 - 061623 - 9 Jump up ^ `` Free articles and software on drainage of waterlogged land and soil salinity control ''. Retrieved 2010 - 07 - 28. Jump up ^ Salt - Affected Soils and their Management, FAO Soils Bulletin 39 ( http://www.fao.org/docrep/x5871e/x5871e00.htm ) Jump up ^ Alan D. Blaylock, 1994, Soil Salinity and Salt tolerance of Horticultural and Landscape Plants. University of Wyoming Jump up ^ Government of Alberta, Salt tolerance of Plants Jump up ^ : 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. Jump up ^ 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 : ( 1 ) Jump up ^ 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 ( 2 ) Jump up ^ Collection of salt tolerance data of agricultural crops from measurements in farmers ' fields. On line : ( 3 ) Jump up ^ 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. External links Article on water and salt balances in the soil Download leaching model for saline soils Salt of the Earth Documentary produced by Prairie Public Television Topics in soil science Main fields Pedology Edaphology Soil physics Soil mechanics Soil chemistry Soil biology Soil zoology Soil ecology Soil morphology Environmental soil science Agricultural soil science ‎ Soil topics Soil Pedosphere Pedodiversity Pedogenesis Soil erosion Soil contamination Soil retrogression and degradation Soil compaction Soil compaction ( agriculture ) Soil salinity Alkali soil Soil pH Soil acidification Soil health Soil life Soil biodiversity Soil quality Soil value Soil fertility Soil resilience Soil color Soil texture Soil structure Pore space in soil Pore water pressure Soil crust Soil horizon Soil biomantle Soil carbon Soil gas Soil respiration Soil organic matter Soil moisture Soil water ( retention ) Soil type Soil classification USDA soil taxonomy Alfisols Andisols Aridisols Entisols Gelisols Histosols Inceptisols Mollisols Oxisols Spodosols Ultisols Vertisols World Reference Base for Soil Resources ( 1998 -- ) Acrisols Albeluvisols Alisols Andosols Anthrosols Arenosols Calcisols Cambisols Chernozem Cryosols Durisols Ferralsols Fluvisols Gleysols Gypsisols Histosol Kastanozems Leptosols Lixisols Luvisols Nitisols Phaeozems Planosols Plinthosols Podzols Regosols Solonchaks Solonetz Stagnosol Technosols Umbrisols Vertisols Other systems FAO soil classification ( 1974 -- 98 ) Unified Soil Classification System AASHTO Soil Classification System Référentiel pédologique ( French classification system ) Canadian system of soil classification Australian Soil Classification Polish Soil Classification 1938 USDA soil taxonomy List of U.S. state soils List of vineyard soil types Types of soil Applications Soil conservation Soil management Soil guideline value Soil survey Soil test Soil governance Soil value Soil salinity control Erosion control Soil policy Soil policy ( Victoria, Australia ) Agroecology Liming ( soil ) Related fields Geology Geochemistry Petrology Geomorphology Geotechnical engineering Hydrology Hydrogeology Biogeography Earth materials Archaeology Agricultural science Agrology Societies, Initiatives International Union of Soil Sciences Soil and Water Conservation Society National Society of Consulting Soil Scientists Soil Science Society of America National Society of Consulting Soil Scientists Australian Society of Soil Science Incorporated International Year of Soil World Congress of Soil Science See also Land use Land conversion Land management Vegetation Infiltration ( hydrology ) Groundwater Crust ( geology ) Impervious surface / Surface runoff Wikipedia : WikiProject Soil Category soil Category soil science Index of soil - related articles List of soil scientists NDL : 00561940 Retrieved from `` https://en.wikipedia.org/w/index.php?title=Soil_salinity&oldid=801114813 '' Categories : Soil science Salts Environmental soil science Energy conversion Alternative energy Water and the environment Talk Contents About Wikipedia Azərbaycanca Български Català Čeština Deutsch Eesti Español Esperanto فارسی Français 한국어 Հայերեն हिन्दी Bahasa Indonesia Italiano עברית Magyar मराठी Nederlands 日本 語 Norsk nynorsk Português Română Suomi தமிழ் Українська Tiếng Việt 中文 Edit links This page was last edited on 17 September 2017, at 19 : 09. 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Question: describe how soil damage due to salinity could be reduced
Answer: by leaching soluble salts