Potassium (K) fertilizer is commonly added to improve the yield and quality of plants growing in soils that are lacking an adequate supply of this essential nutrient. Most fertilizer K comes from ancient salt deposits located throughout the world. The word "potash" is a general term that most frequently refers to potassium chloride (KCl), but it also applies to all other K-containing fertilizers, such as potassium sulfate (K?SO?, commonly referred to as sulfate of potash, or SOP). And there are many kinds of sulfate raw material for different usages, such as potassium sulphate, magnesium sulphate, zinc sulphate, ammonium sulphate, etc. http://www.crownchampion.com/sulfate-raw-material/