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salinization, salinisation — English
The process whereby soluble salts (certain types of chemical substances) accumulate in the soil. It is a serious environmental problem in regions with a warm, arid (dry) or semi-arid climate. All natural waters – including groundwater – contain varying amounts of soluble chemical compounds called “salts”. These compounds include NaCl (ordinary table salt), other chlorides, carbonates and sulphates of sodium, calcium and magnesium. Many soils also contain soluble salts and when groundwater passes through such soil, it dissolves some of the salts and its salinity increases. Where the climate is warm and dry, the water evaporates out of the soil profile, but the soluble salts remain behind. Every repetition of this process increases the salinity of the soil until it is totally infertile and cannot support any plant growth. Irrigation in unsuitable regions has rendered millions and millions of hectares of land throughout the world unproductive and useless. In arid and semi-arid regions irrigation is necessary in order to produce food, but it has to be judiciously done in order to maintain soil fertility. The type of soil and the salinity of the irrigation water have to be studied and the irrigation should be done in a way that will not increase the salinity of the soil. Certain soils should never be irrigated and certain water should never be used for irrigation. Salinisation happens all over the world, but owing to its aridity Africa is particularly prone to the problem. It is interesting to note that enormous, circular regions of salinisation occur around all of the oases (wells made in the desert to extract water, and marshy areas where free-flowing water might be obtained) in the Sahara desert. At all of these places the watertable is close enough to the surface that the water can be extracted by means of shallow wells and for thousands of years people have used these regions to cultivate crops because it was possible to irrigate the land around these water sources. Nowadays most of these areas are completely barren as a result of salinisation. The water is still available, but the soil is so saline that absolutely nothing will grow there. The age-old image of an oasis is that of a clump of palm trees and reeds surrounding a water source where shade, food and water could be enjoyed in the midst of the harsh, dry, hot, lifeless desert. “An oasis in the desert” has even become an often used idiom. Unfortunately, those idyllic oases do not exist anymore and soon no-one will understand the idiom anymore!
