Gypsum (calcium sulfate) is a product that supplies the crop in the soil with a soluble and available form of calcium (Ca2+) and sulfur (SO42-). If these forms are deficient in soil, then crop productivity will benefit if gypsum is applied. Today gypsum is sold either as ag-gyp or pelletized gypsum.
Most commercial dry soil fertilizers contain nitrogen, phosphorus, potassium and sulfur. Dry one is processed into prills, granules or pellets of a particular size and density so it can be absorbed into the soil easily. There are several advantages in creating a standardized granule, including reduced dust is that dust, ease in commercial blending, ease of handling and spreading, and these materials can be blended together without fear that materials will segregate and separate creating uneven distribution.
Ag-gyp is ground down to a coarse mesh (40 to 100 mesh) and as a powder has to be spread alone using specialized broadcast spreaders built for lime. Ag-gyp cannot be blended with other fertilizers as the particle sizes are different which will lead to more ag-gyp flowing out early and more gypsum fertilizer flowing out later into the soil.
Pelletization of gypsum is done by taking quality coarse ag-gyp and finely grinding it (to 200 mesh) and adding a special binding agent to form pellets that hold together in the bin, but break down quickly under soil or field conditions. This process produces high quality gypsum pellets for easy, clean, accurate application.
Pelletized gypsum (calcium sulfate) can be easily blended with today’s dry fertilizer materials including urea, ammonium sulfate, diammonium phosphate (DAP) or monoammonium phosphate (MAP). Soil agricultural retailers with dry fertilizer plants and blenders will formulate a blend based on how many pounds of nutrients and gypsum you want per acre soil. Additionally, the gypsum pelletizing process makes it possible to blend humates, nitrogen, phosphorus and potassium and create granules with a specific analysis.