Agriculture. a whitish layer of mineral salts, especially sodium sulfate, sodium chloride, and magnesium sulfate, often occurring on top of soils where rainfall is low.
refined soda ash.
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refined sodium carbonate
any of several mineral salts, esp sodium sulphate, sodium chloride, and magnesium sulphate, that often appear on the surface of soils as a whitish layer in dry conditions
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012