Symbol: Ca. A soft metal element, atomic number 20, atomic weight 40.08. It is essential to plant growth due to its role, in the form of calcium pectate, in the development of the middle lamella. Calcium ions increase the rigidity of the cell wall by cross-linking the carboxyls of adjacent chains of pectic acid. Calcium is also found as crystals of calcium oxalate in many plant cells. Calcium deficiency is first apparent in the younger parts of the plant because there is little or no translocation of calcium from mature tissues to the growing points.
Calcium is easily leached from soils resulting in an acid soil. This may be countered by adding calcium carbonate, calcium hydroxide (slaked lime), or calcium sulphate (gypsum) to the soil. These compounds also help improve soil structure (see liming