Potash accounts for 90% of all the potassium applied to farmland soil in the U.S. in the form of Muriate of Potash (MOP). Potash ore is mined from a half mile beneath the Earth's surface with Canada leading global potash production, followed by Belarus, Russia, and China. Once potash ore has been brought to the surface, it can be processed in one of two ways.
White potash is the result of a dissolution and recrystallization process. The ore is dissolved under pressure in hot brine and when the mixture cools, white MOP containing 98% potassium chloride is the produced.
Red potash is first crushed very finely to produce single mineral grains. It is then put through a floatation process and red MOP is skimmed off the top. Traces of iron ore remain in red MOP, giving it a reddish or pink hue, yielding 95% potassium chloride.
Agronomically the two are basically the same. Both red and white MOP lend valuable potassium and chloride to the soil and are equally soluble. Each of the two contain around 47% chloride but because of the process of dissolution and recrystallization that white potash undergoes, red potash tends to be less expensive and more readily available, making it the number one MOP choice for most U.S. growers.