Research at Michigan State University and Kansas State University has shown that micronutrient uptake is not enhanced by polyphosphate materials. The efficiency of polyphosphates is considered to be equal to, but not better than, the orthophosphates with more than 80 percent water solubility. Nearly two-thirds is used for direct application, and the remainder is used in granulating processes or bulk blending of mixed fertilizers. The fine-size material is used primarily for liquid suspensions. Standard, coarse and granular sizes are used for granulating processes, bulk blending and direct application.
Potash varies in color from pink or red to white depending on the mining and recovery process used.
White potash, sometimes referred to as soluble potash, is usually higher in analysis and is used primarily for making liquid starter fertilizers. Potassium sulfate in some research studies has improved specific gravity of potato tubers. Potassium sulfate may also be source of sulfur when sulfur is required. If may also be used as a source of sulfur. Potassium hydroxide, also known as caustic potash, is used to a limited extent in the production of liquid mixed fertilizers.