Natural Occurrence
Salt is a natural element of soils and water. 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 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.
Read more about this topic: Soil Salinity
Famous quotes containing the words natural and/or occurrence:
“Poetry is the most direct and simple means of expressing oneself in words: the most primitive nations have poetry, but only quite well developed civilizations can produce good prose. So don’t think of poetry as a perverse and unnatural way of distorting ordinary prose statements: prose is a much less natural way of speaking than poetry is. If you listen to small children, and to the amount of chanting and singsong in their speech, you’ll see what I mean.”
—Northrop Frye (1912–1991)
“One is absolutely sickened, not by the crimes that the wicked have committed, but by the punishments that the good have inflicted; and a community is infinitely more brutalised by the habitual employment of punishment than it is by the occasional occurrence of crime.”
—Oscar Wilde (1854–1900)