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How to prevent tomato umbilical rot
Umbilical rot is a common physiological disorder that affects tomato crops. It is characterized by a black, dry area around the umbilical region of the fruit. This condition typically occurs due to a deficiency of calcium in the fruit. Since the center of the fruit has the lowest calcium content, symptoms usually appear there first and then spread toward the umbilicus.
**Causes of Umbilical Rot:**
1. **High temperatures** can increase leaf transpiration, causing more calcium to be transported to the leaves rather than the fruit. High temperatures also accelerate fruit growth, leading to a relative decrease in calcium levels within the fruit, which makes it prone to umbilical rot.
2. **Drought conditions** reduce water uptake by the plant, and since calcium absorption is closely linked to water uptake, this leads to lower calcium availability for the fruit.
3. **High salinity** in the soil or nutrient solution can interfere with calcium uptake. As salt concentration increases, so does the incidence of umbilical rot. Different plant species vary in their sensitivity to high salinity.
4. **Low root zone temperatures** can slow down root metabolism, reducing the plant’s ability to absorb both water and calcium, ultimately contributing to the development of umbilical rot.
5. **Excess potassium, magnesium, or ammonium** in the soil can create competition for calcium uptake. When these ions are present in high concentrations, they can hinder the plant's ability to absorb calcium effectively.
6. **Insufficient calcium** in the soil or hydroponic solution (below 100 ppm) can lead to widespread umbilical rot. Maintaining a minimum calcium concentration of 100 ppm is crucial for preventing this issue.
7. **Low pH levels** can negatively affect calcium availability. Calcium becomes more available as the pH increases, especially within the range of 5.6 to 8.0.
8. **High humidity** reduces leaf transpiration, which is essential for the passive movement of calcium into the fruit. Lower transpiration means less calcium is delivered to the fruit, increasing the risk of umbilical rot.
To prevent umbilical rot in tomatoes, several strategies can be implemented:
- Ensure **good ventilation and light** to manage humidity and temperature.
- Maintain **rhizosphere temperatures** between 18–20°C during the fruiting stage.
- Keep **soil moisture consistent** to avoid stress on the plant.
- Maintain a **soil pH above 5.5** to optimize calcium availability.
- If umbilical rot appears, applying a **0.4% calcium chloride spray** directly to young fruits can help alleviate the condition and improve fruit quality.
By addressing these factors, growers can significantly reduce the occurrence of umbilical rot and improve overall crop health.