Calcium is a key component of cells holding the structure of cell walls and stabilizing cell membranes. It also has a direct influence on the salt balance within plant cells and activates potassium to regulate the opening and closing of stomata to allow water movement from the plant.
Calcium enhances pollen germination; regulates some enzyme systems; and influences the growth and health of cells and conductive tissues. It has a key specific influence on tomato fruit quality especially Blossom End Rot (BER).
Calcium and yield
Calcium is required for growth and yield and promotes the earliness of fruit development, as studies in Italy show.
Top-dressing with calcium and Ca content in the fruit
The small amounts of calcium found in fruit are essential for the production of good quality tomatoes. Top-dressing with calcium nitrate is a successful method of boosting calcium in fruit, as trials in USA show.
Calcium and fruit firmness
Calcium is needed to maintain good fruit structure and quality. Adequate supplies improve tomato firmness and increases TSS, as shown in studies in Turkey.
Calcium uptake and ammonium
Ammonium based fertilizers are antagonistic to calcium uptake. They reduce soil pH and water uptake rate as well as slowing transpiration. When ammonium competes for uptake with calcium, it increases BER risks.
Calcium and BER
A lack of calcium is intrinsically linked to occurrence of BER. The use of ammonium as the main source of nitrogen, significantly increases the incidence of this disorder, as you can see in studies in Brazil.
Calcium nitrate and BER
As a general rule, fresh fruit with a calcium concentration of above 0.12% do not develop BER. The best way of ensuring good calcium supply is to use calcium nitrate as the calcium source (see data above from Turkey).
General guidelines for calcium application
Calcium is required in relatively large amounts. In total around 152lb/ac of calcium is taken up by a filed tomato crop yielding around 44.6t/ac. As calcium is needed during the whole growth period and its transport into the fruits is slowly, it is common practice to use applications throughout the season to build up levels in the crop tissue and again during fruit maturation, maximizing quality potential and storability.
|Calcium at tomato growth stages
||Boosts root and leaf growth
||Maintains vigorous plant growth
|Flowering – fruit set
||Maximizes crop reproductive development
|Fruit ripening - maturity
||Maintains good fruit firmness and quality and reduce BER risks