Calcium is present in all organs and tissues of plant organisms in the form of mineral salts and organic compounds. It accumulates mainly in the leaves and stems and less in fruits and seeds. As the organs and tissues age, their amount in them increases.
Calcium is equally necessary for the normal development of the root system of plants and their aboveground mass. It has been found that in the presence of calcium in the soil solution, plants better tolerate the presence of hydrogen ions. In case of calcium deficiency, the absorption of ammonium and nitrate nitrogen by plants is strongly suppressed. In the aboveground organs of plants calcium is associated with photosynthesis and growth.
Calcium is of great importance for the physicochemical properties of the soil. It has a positive effect on the reaction and stability of soil structure and plant nutrition.
Calcium is taken from the roots of plants in the form of ions (Ca2 +). The need of cultivated plants for calcium is different. Some of them with the yields export 2-3, and others up to 50 kg per decare of calcium. Unlike nitrogen, phosphorus and potassium, calcium is not reused by plants, so it does not move from aging to younger and more active organs and tissues.
In case of calcium deficiency, plant growth is inhibited. The tips of the young leaves turn down, and necrosis develops on their periphery, which turns into a brown burn. The roots do not form lateral branches and their root hairs turn into a mucous vitreous mass.
Calcium in the soil is contained in the following forms: non-weathered minerals (plagioclase, biotite, etc.), the weathering of which releases some of the calcium; sparingly soluble compounds formed by weathering of primary minerals (calcium carbonate, tricalcium phosphate, calcium sulfate, etc.); water-soluble salts (calcium nitrate, calcium bicarbonate, etc.) and exchanged calcium. In the soil, calcium carbonate, soluble calcium salts and calcium exchange move through the leaching processes in the lower horizons. The only process that partially opposes this leaching is the transfer of calcium from the lower soil horizons to the arable land through the activity of the root system of higher plants.
Calcium ions of its water-soluble salts are easily accessible to plants, but their amount is insufficient. Calcium nutrition of plants is carried out mainly with exchange ions from the absorbing complex of the soil.
Usually plants do not suffer from a lack of calcium food, as soils contain enough calcium in digestible form. Fertilization with calcium fertilizers is mainly used to improve the physicochemical properties of acidic and alkaline soils.
