In order to supply itself with potassium chloride, the raw material for producing potassium nitrate, SQM began to operate in the Salar de Atacama in 1990's. The initial investment included construction of a potassium chloride and potassium sulfate plant, among other facilities.

The Potassium business line currently includes sales of two potassium fertilizers: potassium chloride and potassium sulfate. In 2011, this segment represented approximately 26% of SQM's total revenue. The main resources of potassium that exit in the market to be used in fertilizers are: potassium chloride (KCI), potassium sulfate (K2SO4) and potassium nitrate (KNO3). Of these sources, potassium chloride is without a doubt the most important around the world. SQM is the unique company that produces the three sources of potassium