The element calcium (Ca) is the fifth most abundant element in the earth’s crust and the third most abundant metal after iron and aluminum. It is a Group 2 member of the Periodic table. Calcium along with magnesium, beryllium, strontium, radium, and barium, are known as alkaline earth metals. These metals react with other chemicals at standard temperature and pressure, usually with an overall release of energy. In plants calcium is an essential secondary macronutrient, needed in moderate amounts and is rarely limiting in crop production.