ABSTRACT
Calcium (Ca) is one of the most abundant elements in the earth’s crust (4.15% by weight), where it is present in minerals such as limestone (calcium carbonate, CaCO3), gypsum (calcium sulfate, CaSO4), apatite (various calcium phosphates), and uorite (calcium uoride, CaF2). Although the agricultural benets of adding ground limestone to acid soils to increase crop yields had been known for two millennia, it was not until 200 years ago that Carl Sprengel (1787-1859) is credited with concluding that Ca is an essential element for plants, without which they are unable to grow or complete their life cycles (Pilbeam and Morley, 2007).
