Fast Acting Gypsum starts working immediately to loosen clay and other compact soils giving you more workable soil. It also helps repair salt damaged soils and improves water penetration and root development. Contains Earth Sciences patented Nutri-Bond Technology, which naturally bonds with the soil to help keep more product where you put it. Thats better for the environment and helps your lawn get the most out of every application. 2.5lb covers 500 sq ft. 25lb covers 5,000 sq ft.