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How to prevent tomato umbilical rot
Umbilical rot is a common physiological disorder in tomato cultivation. It manifests as a black, dry spot on the umbilical region of the fruit. This condition is typically caused by a deficiency of calcium in the fruit. Since the middle part of the fruit contains the least amount of calcium, symptoms usually appear there first and then spread toward the umbilicus.
Causes of umbilical rot include:
1. High temperatures can increase leaf transpiration, causing more calcium to be transported to the leaves rather than the fruit. At the same time, high temperatures accelerate fruit growth, leading to a relative decrease in calcium availability in the fruit, which increases the risk of umbilical rot.
2. Drought conditions reduce water uptake by plants, which in turn limits calcium absorption since calcium is primarily taken up passively with water. When soil moisture is low, the plant's ability to absorb calcium decreases.
3. High salinity levels in the soil can interfere with calcium uptake. As salt concentration increases, so does the incidence of umbilical rot. Different plant species have varying levels of sensitivity to salinity.
4. Low root zone temperatures can slow down root metabolism, reducing both water and calcium absorption, which contributes to the development of umbilical rot.
5. Excessive amounts of potassium, magnesium, or ammonium in the soil can create competition for calcium uptake, as these ions often have similar absorption pathways.
6. Insufficient calcium in the soil or nutrient solution (below 100 ppm) can lead to widespread umbilical rot. To prevent this, it’s essential to maintain a calcium concentration of at least 100 ppm.
7. A low pH level can also hinder calcium absorption. Calcium becomes more available to plants as the pH rises, with optimal absorption occurring between 5.6 and 8.0.
8. High humidity reduces leaf transpiration, which is necessary for calcium transport within the plant. When humidity is too high, less calcium is absorbed, increasing the likelihood of umbilical rot.
To prevent umbilical rot in tomatoes, growers should implement several strategies: ensure good ventilation and light exposure to reduce humidity, maintain rhizosphere temperatures between 18–20°C during fruiting, manage moisture levels carefully, keep soil pH above 5.5, and apply a 0.4% calcium chloride spray to young fruits if symptoms appear. This treatment has proven effective in addressing calcium-deficiency-related umbilical rot.