Gypsum: an old product with a new use | Integrated Crop
Gypsum is calcium sulfate (CaSO4). Refined gypsum in the anhydrite form (no water) is percent calcium (Ca) and percent sulfur (S). Usually, gypsum has water associated in the molecular structure (CaSO4#183;2H2O) and is approximately percent Ca and percent S (plaster of paris). Gypsum fertilizer usually has other impurities so grades are approximately 22 percent Ca and 17