Soil salinity is the salt content within the soil; the process of increasing the content of salt is known as salination. Salt is a natural element of water and soils. Salination can be a result of natural processes such as the gradual withdrawal of an ocean or mineral weathering. It can be caused by artificial processes such as irrigation as well.
Soils that are affected by salt are a result of excess accumulation of salts, normally most obvious at the surface of the soil. Salts can be transported to the surface of the soil by capillary transport from a salt burdened water table and then build up as a result of evaporation. They can be concentrated in the soils because of human activity as well, for example the use of potassium as a fertilizer, which can create sylvite, a naturally occurring salt. As soil salinity increases, the salt effects can cause degradation of soils and vegetation.
The consequences of salinity are detrimental effects on plant growth and yield, damage to infrastructure, reduction of water quality, sedimentation issues, and soil erosion ultimately, when crops are too strongly affected by the amount of salts.
Salinity is a significant land degradation issue. Soil salinity can be reduced by leaching soluble salts out of the soil with excess irrigation water. Soil salinity control involves watertable control and flushing combined with tile drainage or another type of subsurface drainage. An inclusive treatment of soil salinity is available from the FAO. High soil salinity levels can be tolerated if salt-tolerant plants are grown. Sensitive crops already lose their vigor in slightly saline soils, the majority of crops are negatively affected by saline soils, and only salinity resistant crops flourish in severely saline soils.
Image Caption: 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. Credit: USDA Employee/Wikipedia