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Nutrient Deficiencies

The visual symptoms of nutrient deficiencies in tomato and other crops can be similar and confusing. We have tried here to provide you with a list of telltale signs to look out for. 

Where soil condition is good and adequate preparation has taken place such as digging in a good general fertiliser or organic manure, maintaining nutrient levels will require regular top-up feeding.

Crops with a heavy fruit load will use up more nutrients, especially potash. Liquid feeding when watering or adding organic or artificial top dressing will help to maintain nutrient levels.

Nitrogen Deficiency

  • In tomatoes leaves turn pale green and growth is stunted. Lower leaves become yellow and areas of purple pigmentation will develop.
  • Peppers will have similar symptoms but usually without the purple colouring.
  • With cucumbers new leaves are smaller than expected and yellow green.
  • In lettuce plants the outer leaves will turn a yellow green colour.

Phosphorus Deficiency

  • Growth is poor in tomatoes and the underside of the new (younger) leaves will start to turn purple or a blue/green colour. However with some varieties the purpling of the leaf stalk (petiole) is a trait of the variety.
  • If the deficiency is severe then the upper and lower surface of the leaves will turn purple. If the plant has been exposed to low temperatures it may display similar symptoms.
  • New leaves in cucumbers will be smaller than expected, but still green in colour.
  • Peppers will keep their green leaf colour but again new leaves will be smaller than expected.
  • In winter grown lettuce, phosphorus deficiency will result in small stunted plants. In fast growing summer varieties outer leaves can turn yellow and you may notice a browning in the interveinal areas of the leaves and at the leaf edge.

Potassium Deficiency

  • Potassium is critical for good quality fruit in tomatoes, peppers, cucumbers and strawberries.
  • The first indication of deficiency is when the edges of the upper leaves begin to turn yellow and eventually brown.
  • If there is fruit on the plant you may notice it ripening unevenly, although there are other factors which cause uneven ripening.
  • In lettuce you may notice the outer leaves turning brown, but reduced plant growth may not be obvious.

Calcium Deficiency

  • The most obvious sign of calcium deficiency is blossom end rot, a large leathery spot which develops on the bottom of the fruit.
  • Calcium deficiency can also be identified by a browning of the leaves at the base of the leaflets. In some varieties the tips of the leaves turn yellow before any browning occurs.
  • Blossom end rot can be identified in maturing fruits and if evident you should remove the fruit as it will be inedible.
  • In lettuce growth will be stunted and you may notice small black/brown spots on the plant.

Magnesium Deficiency

  • Magnesium deficiency is very common in tomatoes as a result of the large amount of potassium needed for good fruit quality.
  • The areas in the leaf between the veins turn yellow, while the veins and leaf edges remain green. This will originate in the bottom and middle of the plant working its way upwards. These symptoms are similar for peppers and cucumbers.