Natural Sulfate of Potash, Magnesia (2MgSO4 ? K2SO4) also referred to as Sul-Po-Mag or K-Mag (these are brand names), is a natural mineral salt, called Langbeinite, and typically contains 22 percent potash, 11 percent magnesium and 23 percent sulfur. Like sulfate of potash, Sul-po-mag is soluble and is an acceptable material to use in the production of certified organic crops and the practice of organic land care.
General Application Guide: There is 1 pound of potash and 1/2 pound of magnesium in every 4 1/2 pounds of langbeinite. Use according to need.