Monday, 19 April 2010

Know Your Nutrients - Feeding Tomatoes

There are three macro nutrients, three secondary nutrients and six micro nutrients.

The secondary and micronutrients are sometimes called trace elements and are not always present in tomato food, although they should be present in a good quality tomato feed and compost.

The problem is, tomato plants are heavy feeders and will require all twelve elements after the food in your grow bag or container has been used up. So check the contents of your tomato food and if it doesn’t contain all of the elements listed below, supplement it with a general feed such as miracle grow or some other plant food that contains trace elements.

Macro N-P-K

Nitrogen (N)   Macro nutrient - Under nitrogen deficiency, the older mature leaves gradually change from their normal green appearance to a much paler green. As the deficiency progresses these older leaves become uniformly yellow (chlorotic). Stunted growth and purpling/reddening along the veins on the underside of larger leaves.are also symptoms.

Phosphorus (P)   Macro nutrient - a distinct purpling of the stem, petiole (leaf branches) and the under sides of the leaves. If deficiency is severe, leaves can develop a blue-gray luster and growth may be stunted.

Potassium (K) Macro nutrient - Leaves show marginal tip burn (necrosis) and again, growth may be stunted.


Magnesium (Mg)  Secondary -magnesium deficiency generally starts with mottled yellowing (chlorotic) areas that develop in between the leaf veins. As the deficiency progresses, small brown patches develop in the yellow areas.

Calcium (Ca)  Secondary - show dying areas (necrosis) around the base of the leaves. Yellow/brown spots may also appear on the edge of leaves. These spots can also be surrounded by a sharp brown outlined edge. This often affects the older leaves first.

Sulfur (S) Secondary - The veins and petioles (leaf branches) show a very distinct reddish colour. and leaves turn yellow.


Iron (Fe)  Micro nutrient - show strong chlorosis (yellowing) at the base of the leaves with some green netting. Symptoms may also show yellowing of young leaves, while the veins remain green.

Manganese (Mn)  Micro nutrient - Shows a light chlorosis of the young leaves and netted veins of the mature leaves especially when they are viewed through transmitted light.

Boron (B) Micro nutrient - Younger leaves show a light yellowing/browning. A cluster of leaves develop in the same place. Leaf margins twist and leaves become brittle.

Copper (Cu)  Micro nutrient - Copper-deficient leaves  are curled, and their petioles bend downward. Leaves show a wilted appearance with yellow to brown patches. Mature leaves may become bleached between the veins.

Zinc (Zn)  Micro nutrient - The younger leaves become yellow and pitting develops in the interveinal upper surfaces of the mature leaves. Older leaves develop brown patches in between the veins. Young leaves very small and develop in a cluster in the same space.

Molybdenum (Mo)  Micro nutrient - Leaves show some mottled spotting along with some interveinal chlorosis (yellowing). An early symptom for molybdenum deficiency is a general overall chlorosis, similar to the symptom for nitrogen deficiency but without the reddish coloration on the undersides of the leaves. Upward cupping of the leaves may also be seen.
You will notice that deficiencies show themselves usually on the lower leaves first. That’s because plants put all they have into top growth first and lower, older leaves tend to be second in the queue!

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