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Trace Elements

Secret traces


Gardeners are often advised to add nutrients and trace elements to the soil before planting, especially before planting edible plants. Why? Linda has the answers.


We all want a bountiful and delicious harvest from our fruits and vegetables. To provide this for us, plants need us to provide them with a steady supply of nutrients and minerals, known as trace elements. These elements, required in only small amounts, can make all the difference.


The Ross Family vegetable patch. We are often told to add nutrients and trace elements to the soil before planting next season’s crops. Needed in only small amounts they can sometimes be the difference between a good crop and a poor crop. Now is the time to add them into your soil before the planting of warm season vegetables. Photo - Linda Ross


Main nutrients

Nitrogen (N)

Put simply nitrogen makes the leaves and stems grow like crazy. A deficiency produces a yellowing of older, lower leaves and a stunting of the growth. Too much nitrogen will result in such speedy leaf and stem growth that plant tissues will be soft and floppy, making them more susceptible to insects and disease. Legumes, such as broad beans and peas, capture nitrogen from the air and deposit it in the soil in which they grow.


Potassium (K)

Potassium keeps the juice pumping through the plant, helps your plants during difficult times (very low or high temperatures, lack of water and during disease attack) and gives fruit and seed production a push along. Deficiency produces irregular growth and brown edges on leaves. But beware – too much potassium slows fruit production. Potassium also speeds the compost process, improves drainage in heavy soils, and improves water retention in sandy soils.


Phosphorus (P)

Phosphorus makes the roots strong and gives flowering a boost. It also promotes energy storage and transfer within plants. A deficiency sees purplish colouring in leaves and stunted roots.


Medium Nutrients

Calcium (Ca)

Calcium deficiency symptoms appear as stunted plant growth, dead leaf margins on young leaves or curling of the leaves, and eventual death of terminal buds and root tips. Generally the new growth of the plant is affected first.

Fix a deficiency by adding agricultural lime to acid soils, aiming at a pH of 6.5, unless the plant in question specifically prefers acidic soil.

Calcium prevents ‘blossom end rot’ in tomatoes and zucchini, internal browning in cabbage and Brussels sprouts, stunted growth in celery and cavity spot in carrots.


'Blossom end rot' – Symptoms start as sunken, dry decaying areas at the blossom end of the fruit, furthest away from the stem, not all fruit on a truss is necessarily affected. Sometimes rapid growth from high-nitrogen fertilisers may cause blossom end rot. Photo - Linda Ross


Sulphur (S)

Sulphur is important in keeping growth going strong. Sulphur deficiency is very similar to magnesium deficiency: the leaves exhibit a yellowing of the edges and veins; but in the case of sulphur deficiency it’s the youngest leaves that are affected first.


Trace Elements

Iron (Fe)

Iron is a key catalyst in chlorophyll production, which makes the leaves green. Iron deficiency turns new leaves pale yellow or white while the veins remain green. A high soil pH prevents plants from absorbing iron. If necessary it can be applied as a soluble form of iron chelates.


Magnesium (Mg)

Magnesium is another key constituent of chlorophyll and without chlorophyll and thus photosynthesis, there could be no growth or harvest. But magnesium is not only used for chlorophyll, it is equally used for other vital processes and above all for the formation of carbohydrates, proteins, oils and vitamins. It is also essential for cell division within the plant.

Potato, tomato and beetroot are the crops most affected by a magnesium deficiency. The first sign of deficiency is yellowing between the veins on the older leaves. Later the yellow leaves brown, wilt, dry-up and fall. In some varieties leaves die without first yellowing.

When tomatoes are magnesium-deficient, the leaves become brittle and show a tendency to curl from top to bottom. The veins remain green while the leaf edges turn yellow and die off. Magnesium deficiency adversely affects yield and quality.

If you recognise magnesium deficiency in your crops, ask your nursery to recommend a magnesium-containing fertiliser, either straight or blended with other nutrients.


Boron (B)

Boron is necessary for cell division and protein formation, and also for pollination and seed production. Damage to cell walls is responsible for the brown flecks, stripes and zones associated with boron deficiency in sugar beet (‘heartrot’), swedes (‘brown rot’), carrots (‘five o’clock shadow’) and celery (stripes along stems).


Photo - Tetra Images/


The Fixers

Matured animal manures are one of the most important things to add to the soil as they contain beneficial bacteria and micro-organisms which are essential in helping plants break down and digest nutrients. Manures are good accelerators to aid in the breakdown of composting plant material. Use between 10-20% manure by volume. Naturally pelletised manure, such as that of rabbits and sheep, resists breakdown and makes good mulch. Once aged, manures encourage earthworm activity in soil. Manures also improve the water-holding capacity of sandy soils and open up clays but manures are mild sources of nutrients.
N-P-K (Nitrogen/Phosphorous/Potassium) ratios are low in all manure. Even poultry manure, one of the richest, only has an eighth the nitrogen content of blood and bone. Cow manure is relatively poor in nutrients but it will slightly improve soil fertility. Fertiliser can be made from fresh manure added to a barrel of water and left to brew for four weeks. Break down the liquid to the strength of weak tea and use as a general-purpose fertiliser all around the garden,

Compost is rich in NPK and is packed with micronutrients and microorganisms. It is the cheapest way of improving your soil organically. The downside of primilarily using compost to feed the soil is the high probability of creating more acidic soil. Right this with an application of garden lime sprinkled into the soil to achieve a pH of around 7.

Worm castings or worm wee contain a balance of nitrogen, potassium, phosphorus, trace elements and humates, which are essential soil improvers. Worm castings Also contain bacteria, fungi and protozoa which help promote nutrient uptake into the plant.

Blood and bone is high in nitrogen so fantastic for promoting green growth. It also encourages microorganisms in the soil.

Fishmeal is a great nitrogen-phosphorus all rounder with a lot more N and P than manures. It's higher in phosphorus than blood meal as it includes crushed and processed fish bones. Fish liquid fertilisers are also available.

Liquid seaweed fertiliser is one of the best organic fertilisers, not so much for its levels of NPK, but for the micronutrients and trace elements.

Rock phosphate is literally crushed rock high in phosphorus. Sprinkle it around for a slow up take of phosphorus.

Sulphate of potash sounds like a chemical fertiliser but it's not. This mineral product has a high level of readily available potassium; good for fruiting vegetables, such tomatoes, capsicums and chillies, and fruits. You don’t need a lot – one part sulphate of potash to 10 parts blood and bone meal will give you a great all-round fertiliser. Sulphate of potash is also high in sulfur.

Dolomite, best known as a clay-breaking mineral, is a also a good source of magnesium. Sprinkle it around if you see a magnesium deficiency, following the instructions of the packet.

Garden lime is normally what you add when you want to increase the pH level of your soil, but it is also a handy source of calcium. If you can get your hands on dolomite lime you'll also get an added boost of magnesium.

Gypsum is for very alkaline soils to which you don’t want to add lime and risk further increasing the pH. It's not only a clay breaker, but is also rich in calcium and sulphur.


5 of our favourite fixes

1. Amgrow Organix 4Vital, which is four essential minerals- calcium, boron, phosphorus and magnesium. Water into your crops as they grow.

2. Miracle-Gro All-Purpose Plant Food with NPK and trace elements, is sprinkled on.

3. Amgrow Nutri-blend5 is a balance of NPK and trace elements in an organic form. Apply approximately half a bag per square metre of soil surface.

4. Yates Blood and Bone – contains slow-release nitrogen, and the bone meal is full of calcium and phosphorus. But because it lacks potash you will need to add sulphate of potash (two cups for a bucketful of blood and bone) and apply a large handful for every square metre of veggie garden.

5. Amgrow Harvest, which contains fish fertiliser, seaweed, plant nutrients and fulvic acid (plant hormones) can be watered on with a watering can.


Text: Linda Ross




Pic Caption: [Pic of blossom end rot on Roma tomato]


About this article

Author: Linda Ross