What does Calcium Sulfate (Gypsum) mean?
Calcium sulfate is an inorganic matter that in one form is plaster of Paris and in another form is gypsum. In horticulture, the gypsum form of calcium sulfate is primarily used as a soil conditioner.
Calcium sulfate is a naturally occurring substance that is used frequently to improve the structure of clay soils because it helps prevent the leaching of excess sodium in the soil.
Calcium sulfate is also used in organic lawn care to lower the pH in alkaline soils.
In the form of gypsum, calcium sulfate is a common soil conditioner that helps loosen tight clay soils so they drain more readily.
There are many types of natural soil conditioners available to gardeners; it can be difficult to determine exactly which one is right for your soil conditions. The general rule with gypsum is: If you need to add calcium, do not need the phosphorus boost of say, bone meal, and do not wish to raise your soil pH, gypsum (calcium sulfate) should be used to condition your soil.