Calcium - An essential plant nutrient

With all of the emphasis on N-P-K in agriculture, calcium and magnesium are sometimes overlooked. Calcium and magnesium are essential macro-elements, used in relatively large quantities. In fact, plants take up more calcium than phosphorus!


  • Calcium is much needed in plant growth for below reasons:
  • Participates in metabolic processes of other nutrients uptake.
  • Promotes proper plant cell elongation.
  • Calcium is required for the stability and function of cell membranes and acts as a type of `cementing agent ' in the cell walls in the form of `calcium pectate'.
  • Participates in enzymatic and hormonal processes.
  • Helps in protecting the plant against heat stress - calcium improves stomata function and participates in the induction of heat shock proteins.
  • Helps in protecting the plant against diseases - numerous fungi and bacteria secret enzymes which impair plant cell wall. Stronger Cell walls, induced by calcium, can avoid the invasion.
  • Affects fruit quality.
  • Has a role in the regulation of the stomata.


In hydroponic systems, adequate levels of calcium are usually maintained with calcium nitrate or other calcium salts. Therefore the lowering of calcium levels in the plant tissue and the occurrence of deficiency symptoms usually result from the influence of other factors which impede either calcium uptake or its distribution within the plant. Calcium uptake may be reduced by the competitive effects of a high concentration of other cations such a potassium, sodium, magnesium or ammonium in the solution. And since calcium moves in the xylem tissue, its uptake is also affected by low root temperature and by restricted water movement through the plant caused by high salinity in the media or excessive humidity in the atmosphere.

Higher EC levels in the nutrient solution reduce the uptake of calcium, unlike nitrogen and potassium which increase in concentration in leaf tissue with higher EC levels. Reducing the EC of the nutrient enhances water uptake and with this, more calcium can be taken up and transported within the plant to developing tissue.


  • Calcium deficiency results in marginal yellowing, tiny and deformed leaflets, curled up margins in Tomatoes.
  • White spots form on edges and veins of upper leaves in Cucumbers.
  • Growing point region of youngest leaves remains small, later the leaves shrivel and growing point dies.
  • Blossom end rot is observed in tomatoes while Cucumber buds might abort and finally, plant dies back from the apex.


The simplest means of preventing calcium deficiency disorders such as tipburn and blossom end rot is to maintain adequate calcium levels in a balanced nutritional solution with the correct EC level. Use 0.75% - 1.0% calcium nitrate solution as foliar spray in acute cases. As always, moderation is always recommended when using additives. Start with very low dosages, see how the plants respond and add more if necessary. Keeping the plants stress free, providing gentle air movement across the leaf source to encourage transpiration and preventing excessive temperatures all help drive calcium into leaf tips and developing fruits.

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