Gypsum (CaSO4·2H2O) is a mineral mined from sedimentary deposits created by the evaporation of saline water, where sulfuric acid comes into contact with calcium carbonate. A number of productive gypsum quarries have operated in Michigan’s Lower Peninsula over the last 150 years, marketing the mineral as plaster, stucco and fertilizer. Agricultural gypsum is applied as a soil amendment and fertilizer containing roughly 22 percent calcium and 18 percent sulfur. Most soils in Michigan provide adequate amounts of calcium for soybean production. However, coarse-textured soils with low potential for sulfur mineralization from organic matter may be at risk for sulfur deficiency [...]