Historical Information

The rare earth element calcium is one of the most abundant elements in the lithosphere; it is readily available in most soils; and it is a macronutrient for plants, yet it is actively excluded from plant cytoplasm.

In 1804, de Saussure showed that a component of plant tissues comes from the soil, not the air, but it was considerably later that the main plant nutrients were identified. Liebig was the first person to be associated strongly with the idea that there are essential elements taken up from the soil (in 1840), although Sprengel was the first person to identify calcium as a macronutrient in 1828 (1). Calcium was one of the 20 essential elements that Sprengel identified.

Salm-Horstmar grew oats (Avena sativa L.) in inert media with different elements supplied as solutions in 1849 and 1851 and showed that omitting calcium had an adverse effect on growth (2). However, it was the discovery that plants could be grown in hydroponic culture by Sachs (and almost simultaneously Knop) in 1860 that made investigation of what elements are essential for plant growth much easier (2). Sachs’ first usable nutrient solution contained CaSO₄ and CaHPO₄.

It has been well known since the early part of the twentieth century that there is a very distinct flora in areas of calcareous soils, comprised of so-called calcicole species. There are equally distinctive groups of plant species that are not found on calcareous soils, the calcifuge species (see Section).