Sulfate of Potash (SOP) 0-0-52 is the water-soluble grade potassium sulfate (SOP). It contains 52% K2O and is white in color. SOP 0-0-52 is the highest grade of water solubility and purity and applied as a solution to the soil or sprayed on the plants. Provides a Cl-free source of K2O with the added benefit of supplying sulfur. In alkaline soils, SOP 0-0-52 lowers the pH in the rhizosphere, helping to improve availability of phosphorus and certain trace elements. In drip irrigation systems, it helps to reduce the pH of the irrigation water and prevent nozzle clogging.