Salt-affected soils are visible 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 of the soil. ^[1]

Salt affected soils are caused by excess accumulation of salts, typically most pronounced at the soil surface. Salts can be transported to the soil surface by capillary transport from a salt laden water table and then accumulate due to evaporation; they can also be concentrated in soils due to human activity. Capillaries are the smallest of a body's Blood vessels measuring 5-10 μm in diameter which connect Arterioles and Venules and enable the interchange Evaporation is the process by which Molecules in a Liquid state (e As soil salinity increases, salt effects can result in degradation of soils and vegetation. Salinity is the Saltiness or dissolved salt content of a body of Water. Soils retrogression and degradation in the French school of pedology are two regressive evolution processes associated with the loss of equilibrium of a stable Soil

Salinization is a process that results from:

• high levels of salt in the soils
• landscape features that allow salts to become mobile (movement of water table)
• climatic trends that favor accumulation
• human activities such as land clearing and aquaculture activities

Salt is a natural element of soils and water. Aquaculture is the farming of freshwater and saltwater organisms including Molluscs Crustaceans and aquatic plants Salt is a Dietary mineral composed primarily of Sodium chloride that is essential for Animal life but toxic to most land plants The ions responsible for salinization are: Na⁺, K⁺, Ca²⁺, Mg²⁺ 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 eons, 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. Aswan (Assuan is a city on the first cataract of the Nile in Egypt. 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. Groundwater is Water located beneath the Ground surface in Soil pore spaces and in the Fractures of lithologic formations Erosion is the carrying away or displacement of solids ( Sediment, Soil, rock and other particles usually by the agents of currents such as wind After the construction, the continuous high level of the water table led to the salination of the arable land. In Geography, arable land (from Latin arare, to Plough) is an agricultural term meaning land that can be used for

Salinity from drylands can occur when the water table is between two to three metres from the surface of the soil. Dryland salinity is salinity that occurs in a landscape that is not irrigated as distinct from irrigation salinity and urban salinity. 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 from irrigation can occur over time wherever irrigation occurs, since almost all water (even natural rainfall) contains some dissolved salts. Irrigation is an artificial application of water to the soil usually for assisting in growing crops 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. Drainage is the natural or artificial removal of surface and sub-surface water from a given area Biosalinity is the study and practice of using saline ( salty 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).

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. Erosion is the carrying away or displacement of solids ( Sediment, Soil, rock and other particles usually by the agents of currents such as wind

Salinity is an important land degradation problem. Soil salinity can be reduced by leaching soluble salts out of soil with excess irrigation water. High levels of soil salinity can be tolerated if salt-tolerant plants are grown. A comprehensive treatment of soil salinity is available from the FAO: Salt-Affected Soils and their Management, FAO Soils Bulletin 39 (http://www.fao.org/docrep/x5871e/x5871e00.htm).

From the FAO/UNESCO Soil Map of the World the following salinised areas can be derived. ^[2]

See also

• Atriplex (saltbush) (orache) (orach)
• Geohumus
• Saline seep
• Salinity control
• Salinity in Australia
• Salting the earth
• Soil acidification

References