Gypsum is a calcium sulphate that will improve the soilís properties. It is excellent for lawns, gardens and in the compost. Source of calcium without modifying the pH level. Gypsum helps limit salt damages caused by de-icers (salts) and by excrements from household pets. This amendment improves the quality of the soil and water retention particularly in clay soils. Recommended for use in spring, summer and fall. Does not burn. Harmless to children and pets.