Nitrogen deficiency or excess
Symptoms
When deficient — growth slows down, old leaves lose color, newly growing leaves are yellow-green. Nitrogen is quickly broken down or washed out by water. In case of excess — tomatoes grow many leaves, but bloom little and set fruit sparsely.
Control and prevention
Nitrogen needs to be supplemented in the soil more often than other elements. In case of excess — reduce nitrogen fertilizers.
Related problems
Similar symptoms might indicate a different cause — compare them.
Phosphorus deficiency or excess
Phosphorus is necessary for cell growth, flower and fruit formation. When deficient — young plant leaves darken, acquire a purple hue; the growth of an older plant stops, the underside of the leaves and veins are purple. In case of excess — fruits become bitter.
Magnesium deficiency
Magnesium is an important part of chlorophyll. When it is deficient, the veins of old leaves begin to yellow, while the veins themselves remain green. Later, the symptoms spread to young leaves, which begin to wither.
Potassium deficiency
Potassium is responsible for metabolism in the plant. When deficient — leaves begin to wither, deform, yellow, the stem weakens, fruits fall prematurely. When a young plant is deficient — it grows deformed, the edges of older leaves dry out.