What Is Affecting The Color Of Your Tomatoes?

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What Is Affecting The Color Of Your Tomatoes?

While many factors such as size, hardness and taste are considered crucial characteristics for evaluating tomato varieties, the color of the fruits remains one of the most important factors contributing in the marketing and subsequently good profits of this crop. However, fruit color disorders may result from many overlapping factors, including:

  • Weather (heat and cold),
  • Nutrients (potassium – calcium – magnesium, and other nutrients),
  • Soil quality and percentage of organic matter,
  • Soil pH,
  • Infection with diseases and viruses.

Many names are attributed to these color disorders such as yellow shoulder, internal white tissue disorder, and color blotching. The following is a description of their apparent symptoms:

Yellow Shoulder

The area around the stem becomes yellow or green with a white or green inner tissue.
The exact causative agent is unknown but is associated with adverse weather conditions, soils with low potassium levels, low organic matter and high pH.

It is worth noting that some tomato varieties are more susceptible to yellow shoulder disorder than others. While adverse weather conditions cannot be changed, selecting resistant varieties and following soil testing recommendations are important steps to avoiding the yellow shoulder problem in tomatoes.
Note that soil amendments should not be made without soil testing as too much potassium can reduce the absorption of calcium and magnesium, and too much sulfur (used to acidify the soil) can burn plant roots.

Color Blotching

Parts of the fruit remain yellow or orange as they do not ripen like the remainder of the fruit. The causative agent may be one of the following:
• Temperatures below 15°C
• Compacted soil with too much moisture, which inhibits the root system, limiting the level of ripening of fruits
• Viral diseases
• Invasion of whiteflies

Ripening Failure

Depending on the variety, the color of ripe tomatoes can range from red, orange, pink, yellow, brown and green. However, immaturity and achieving the desired color can occur as a result of several factors, most notably:
• Temperatures less than 15 degrees Celsius or higher than 33 degrees
• Compressed soil and excessive moisture inhibits the root system, which limits the ripening of fruits.
• Low levels of potassium (potassium) prevent proper fruit development and ripening.

General Guidelines

To avoid coloring disorders at the time of maturity where the farmer cannot delay the harvest, it is recommended to take the precautions and apply corrective measures as early as the beginning of the fruit development.

The main preventive measures are:

• To know the soil and its fertility
• To add soil amendments to improve the organic matter contents and maintain them at a high level
• To select varieties that are tolerant of this phenomenon
• To pay attention to the exchanged potassium, exchanged magnesium and calcium in the soil
• To Improve soil conditions in order to increase the potash element or decrease the magnesium element
• To Maintain a pH between 6.2-6.5
• To control greenhouse temperatures and maintain them between  15-30 degrees


It is absorbed by the plant as a K+ moiety, which is an important component in the formation of sugars and proteins and helps in the regulation of water within the plant cells. The plant obtains it from soil organic matter and fertilizers.

It is absorbed from the plant in the form of a binary cation of CA++, which is a very important element for the development of roots and leaves, and acts as a carrier and preservative for other nutrients and also strengthens plant tissues, obtained by the plant from soil, organic matter and fertilizers.

It is absorbed by the plant in the form of a binary cation MG++, which is an essential element in the formation of chlorophyll, and activates photosynthesis and plant enzymes. The plant obtains it from soil minerals, organic matter, fertilizers and dolomitic limestone.

It is the group of exchangeable cations (positive electrolytes, CA++, MG++, K+) that soil and materials can retain. The soil carries a negative charge that protects and prevents excessive washing out of cations. Sandy soils have a weak exchange capacity, while clay and organic loam soils have a high cation exchange capacity.

Maryse Bou Zeid


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