All plants require a range of nutrients to ensure healthy growth. These nutrients are almost always taken up by the roots from the soil in which they are growing. There are seven nutrients which tomato plants require plus a host of trace elements.

The three key elements are listed below with the identifying signs where there is a deficiency. In truth however, there is a large overlap between them and identifying a specific deficiency is not an exact science for the amateur gardener.


NITROGEN DEFICIENCY


The symptoms of a nitrogen deficiency are probably the easiest to accurately identify:
  1. Older leaves begin to turn yellow, young leaves and shoots will still appear green.
     
  2. Affected leaves will develop a bronze tinge to them.
     
  3. The plant will not grow as quickly as normal and side branches will be stunted giving the plant a thin and slightly "sickly" appearance.
     
  4. Leaves will fall off earlier than expected.

CAUSES OF NITROGEN DEFICIENCY


Poor soil with no organic matter in it is the first cause of this deficiency. Sandy soils especially are poor at holding nitrogen. The long-term solution is to add composted organic matter to the soil to improve its texture and allowing it to retain nutrients such as nitrogen.

Normally healthy soils can also be affected by a lack of nitrogen when there have been prolonged periods of rain. Heavy and prolonged rain washes nutrients out of the soil.

CORRECTING NITROGEN DEFICIENCY


For naturally poor soils the best solution is to dig large amounts of well-rotted organic matter into the soil. This will add slow release nitrogen to the soil and improve its ability to make it available to plants. An annual mulch with composted materials will greatly help to maintain the quality of the soil. 

A quick fix is to apply a general purpose liquid fertiliser where the plants are growing. Don't apply too much however, stick to the dosage rate stated on the packet. Too much nitrogen will result in lots of lush leafy growth at the expense of tomatoes. It can also leave the foliage exposed to wind and rain damage as well as pests and diseases.

MANGNESIUM DEFICIENCY


The signs of magnesium deficiency are listed below
  1. The leaf tissue of older leaves has yellow / brown blotches in between the leaf veins.
     
  2. The surface of the leaves will become slightly uneven with raised parts showing the worst of the yellowing.
     
  3. Leaves will fall off earlier than expected..

CAUSES OF MAGNESIUM DEFICIENCY


In common with other deficiencies, sandy or light soils often loose magnesium. Heavy and prolonged rain also washes out nutrients from the soil.



CORRECTING MAGNESIUM DEFICIENCY


The long-term solution to a magnesium deficiency is to add Dolomite limestone (readily available at garden centres) to the soil at the dose recommended on the package. Do not exceed the dose because doing so can result in too much calcium which in turn inhibits the roots ability to absorb the magnesium. Dolomite limestone is a slow release product which lasts for a long time in the ground.

A more immediate remedy for magnesium deficiency is to spray the foliage with a solution of water and Epsom Salts. The ratio is 20g of Epsom Salts added to a litre of water and a few drop of washing liquid will help the spray to stay on the leaves. Spray again after a fortnight.

POTASSIUM DEFICIENCY


The signs of potassium deficiency are listed below
  1. The edges of older leaves start to turn yellow / light brown
     
  2. New leaves are normal
     
  3. If the deficiency is significant, the yellowing affects the entire leaf (veins are unaffected).

CAUSES OF POTASSIUM DEFICIENCY


Lack of organic matter in the soil. Constant growing of crops with feeding the soil, light and sandy soils are most at risk.



CORRECTING POTASSIUM DEFICIENCY


Add organic matter to the soil at least once a year, mulching with plant material also helps. If organic material is not available blood, fish and bone is a good, long-lasting fertiliser.

Quick fixes include liquid tomato plant fertiliser or sulphate of potash.

CALCIUM DEFICIENCY


A calcium deficiency is most obvious in the fruit of tomatoes and the most common is blossom end rot. This deficiency can also be seen in the leaves as distorted and yellow foliage where the join the stem they are attached to. 

Other common pests and diseases which affect tomato leaves include:

  1. Tomato Blight
     
  2. Tobacco Mosaic Virus
     
  3. Nutrient Deficiencies
     
  4. MAIN INDEX TOMATO PESTS AND DISEASE

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