Various salts of potassium, chiefly potassium carbonate, are known as potash. The names caustic potash, potassa, and lye are frequently used for potassium hydroxide. In fertilizer terminology, potassium oxide is called potash. Potash soap is a soft soap made from the lye leached from wood ashes. Canada, Russia, Belarus, China, and Germany are the world’s top producers of potash.