Blossom end rot (BER) is a common physiological disorder that shows as a dark, sunken, leathery patch at the bottom (blossom end) of the fruit. It is most common in tomato, pepper, watermelon, and squash. It is not a disease; the core problem is that calcium cannot be transported to the fruit adequately.
What Causes Blossom End Rot?
Often there is enough calcium in the soil; the real problem is that calcium is not transported to the fruit. The main causes are:
- Irregular irrigation: the most common cause. Dry-wet fluctuation disrupts calcium transport.
- Water stress and extreme heat: rapid transpiration pulls calcium to the leaves, so the fruit gets too little.
- High EC / salinity: makes root water and calcium uptake harder.
- Excess nitrogen (especially ammonium): triggers rapid growth and competes with calcium.
- Excess potassium/magnesium: creates antagonism with calcium uptake.
How Is It Prevented?
- Regular, balanced irrigation: the most effective measure; minimise soil moisture swings. Drip irrigation is ideal.
- Calcium nutrition: apply regular root-zone calcium and a balanced program. Foliar calcium transport to the fruit is limited, so the real solution is irrigation plus root feeding.
- EC management: control salt buildup, especially in hot periods.
- Avoid excess nitrogen: target balanced nitrogen, potassium, and calcium during fruiting.
- Stress management: under heat stress, AminoWork and RapidAlg indirectly help by improving the plant's stress tolerance.
Which Crops Are Affected?
Most often tomato and pepper; also watermelon and squash. For crop-specific prevention, see our tomato fertilization program and pepper fertilization program. Combining the irrigation and feeding plan with our fertigation guide gives the best results.
Blossom end rot is not a disease but a transport problem: at the centre of the solution is not a spray, but regular irrigation and balanced calcium management.
To solve recurring BER in your field, contact our agricultural engineers; let us refine your irrigation and feeding program together.
