Page 140 - E-BOOK English

Solonchaks

Definition

Solonchaks have a high concentration of soluble
salts at some time in the year. These soil are mainly
confined to the arid climate zones and to coastal regions,
including the areas that saline soils and saline-affected
soils are found. Solonchaks have a salic horizon starting
within 50 cm of the surface soil and have no thionic
horizons presented.

Distribution

Solonchaks are found worldwide, about
1,025-2,125 million rais. They frequently occur where
evaporation exceeds rainfall, and there is a seasonal
or permanent water table close to the surface soil,
or in coastal areas as influenced by saline intrusions.
Solonchaks infrequently distribute in Saharan Africa,
East Africa, Namibia, Central Asia, Australia, and South
America.
In Thailand, Solonchaks cover about 552,892
rais, mainly distributing in the northeast region, located
in Nakhon Ratchasima, Sakon Nakhon, and Udon Thani
provinces as well as those areas at the edge of the
sea as affected by salinity.

Formation

Hot, dry conditions cause water containing salts, e.g., sodium or calcium salts,
move upward from the water table to the surface soil. The salts are left after the water
evaporates. Although salts may be leached downwards by rain or by irrigation, the pattern of
salt precipitation is re-established in the dry season or when irrigation is none.

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