Down To Earth Garden Gypsum Calcium Sulphate Dihydrate - 5lbIn Store Location: @B4 Trailers Location: @A 1 (A13) Down To Earth Garden Gypsum 5lbs Down To Earth Garden Gypsum improves the physical condition of landscape, lawn and garden soils while adding calcium and sulfur. Commonly used to reduce soil compaction and increase drainage in heavy clay soils, gypsum is also used to help remediate and revitalize alkaline, sodic or saline soils.