Calcium (Ca) deficiency is a common disorder of plants on acidic soils, but more usually caused by unavailability rather than a shortage. This may be due to water shortages, which slow the transportation of calcium to the plant, or can be caused by excessive usage of potassium or nitrogen fertilisers.

Symptoms include curling of young leaves or shoots and poor growth. Crop-specific symptoms include:

  • Apple- 'bitter pit' (fruit skins develop pits, brown patches appear in flesh and taste becomes bitter. Can occur when fruit is in storage. Bramley apples are particularly susceptible).
  • Cabbage and Brussels sprouts- internal browning.
  • Carrot- 'cavity spot' (oval spots develop into craters which may be invaded by other disease causing organisms).
  • Celery- stunted growth, central leaves stunted.
  • Tomatoes and peppers- 'blossom end rot' (black patches appear on the end of fruit- not all fruit on a truss need be affected).

Calcium deficiency can be rectified by adding lime to acid soils, aiming at a pH of 6.5. Organic matter should be added to the soil in order to improve its moisture-retaining capacity.

Other physiological plant disorders include;