Role of Calcium in Tomato Production

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 effect at growth stages

Stage Calcium effect
Establishment Boost root and leaf growth
Vegetative Growth Maintain vigorous plant growth
Flowering – Fruit Set Maximize crop reproductive development
Fruit Ripening - Maturity Maintain good fruit firmness and quality and reduce BER risks
See more on Tomato Growth Stages.

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 deficiencies in Tomatoes

The most obvious deficiency symptom is BER. However, deficiency results in scorching of the new growth and death of the growing point in both the roots and shoots. The leaves of seedlings become distorted and develop yellow, brown or purple necrotic areas starting at the leaf margin and moving into the interveinal areas. The growing point soon dies. In mature plants, the edges of the youngest leaves become brown, and some interveinal areas turn yellow.

The growing point dies and the flower buds fail to develop. In the field, BER is more frequent on acid soils and those with a high salt content and can also cause vascular breakdown at the base of the plant, leading to wilting. It is prevalent under low soil moisture conditions. Crops grown on calcareous soils will also need calcium, as the element is not necessarily plant available due to its low solubility. Where calcium is supplied in excess, magnesium and potassium deficiencies may arise as a result of nutrient imbalance.

See more about calcium and other nutrients deficiencies in tomatoes on Tomato Crop Nutrition.