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Nutrients, or plant foods, must be designed for hydroponics, meaning they must be made up of the 24 essential technical grade materials which are totally soluble and available to the plant immediately. If you use a fertilizer grade material which is No.3 in the scale of solubility, you will then be in for a long and troublesome hydroponic growing experience! This is because beause fertilizer grade mineral salts require bacteria to break down the more complex elements present into a more soluble form to enable the plant to access them. In a hydroponic environment there are no bacteria present, therefore only the most soluble mineral salts can be used, and these are known as technical grade mineral salts. (The other being 'lab grade' mineral salts which are cost prohibitive to most growers because of the exorbitant cost of raw materials).

The hydroponic plant can take mineral salts in at a lot faster rate than soil grown plants because of the solubility of the materials used. Think of a plant's root zone cell wall as a tennis racket, and a fertilizer grade material is as a bit like trying to get a tennis ball through the tennis racket; technical grade mineral salts are in effect like a marble which easily passes through the tennis racket.

You may have plants that will do well initially in a hydroponic situation by using a fertilizer grade material but the time will come when they will exhibit minor mineral deficiencies, eventually leading to major problems until even changing to a specific hydroponic nutrient will not save your crop. You have, (as they), been warned!

The other concern for the grower is to do with nutrient strength or concentration. If your nutrient is too strong or too weak it will ultimately lead to deficiencies or toxicity and cause the eventual death of your plants. For an example, if your nutrient is too strong it puts too much pressure on the cell wall of the root zone thus inhibiting the ability of the plant to take up, lets say calcium, (and remember, this is only one of many elements), and this will show up in the plant as a deficiency.

On the other hand, if the nutrient is too weak the same deficiency will show up due to insufficient calcium... and just think if this happened to all 24 elements! It is not necessary to throw huge amounts of salts, hormones and vitamins at the plant to achieve a truly excellent result. If you are using a recognized full spectrum nutrient and you follow the directions on the pack you will have a successful growing experience. For the first time grower I would suggest that you follow the game plan and dose your tank as per instructions on the nutrient pack. Once a week feed and top off with water daily, dump tank weekly and repeat the routine. For the more experienced grower who has invested in digital testing equipment, dose the tank daily to the max level recommended, letting the plant take in all the nutrients until the C.F (nutrient strength) levels falls back to the recommended minimal levels before re-dosing the tank.

In indoor plant growth, as discussed on previous pages, you are mother nature, so don't over feed your plants. There is a very defined area within which you can operate, it has its lower level as well as its upper level, and if you add too much of one element it will show up as a toxicity problem. However, if you take the attitude of some extremists in our industry, and starve the plant, then feed the plant again, it will suffer undue stress and not be able to reach its full potential. The best advice is to treat your crop like you treat your kids, your pet's or even yourself, when it comes to nutrition: a balanced diet of a wide variety of foods is always best. If you treat them badly and try to make your own 'concoction', then you are headed for disaster as a hydroponic grower.

Nutrient (plant food) plays an important role in the overall health and well being of the plant, but it's only about 5% of the equation. If you really want to get down to the nuts and bolts of the growing experience I would suggest you concentrate on the air quality, ambient temperature and humidity, which plays much more of a role in determining whether you get a good result... or a great result.

The nutrient solution structure and strength governs health, height, leaf and flower production and has a bearing on all aspects of the plants growth. Granted it has a small part to play in the overall development of the plant compared to light, but an important one none the less. As a general guideline for leaf development, run CF levels between 10 to 16 and for flowering a CF of 22 to 28 is desirable.


Some characteristic nutrient disorder symptoms are:

Nitrogen (Chemical Symbol: N)

Nitrogen is one of the main elements contributing to the growth of a plant. Plants convert nitrogen to produce amino acids and proteins which are used to produce new cell growth. Nitrogen moves easily throughout the plant servicing new growth at the expense of the older foliage. Any deficiency will cause the new growth to become weak and spindly resulting in a stunted plant. The shortage is usually first visible in a plantís older leaves which lose their green colour and gradually become yellow. This is because nitrogen is important for the green oxygen producing chlorophyll pigment in the leaves. As the shortage continues the younger leaves will also become yellow and the veins on the underside of the leaves turn a red or purple colour. Vegetable plants are liable to run to seed. An excess of nitrogen will also affect the fruiting or seed development of most plants.

Nitrogen Deficiency - Leaves will be pale and yellow and the plant is generally weak and spindly.

Nitrogen Excess - Excessive plant growth with poor development of fruiting parts. Plants are dark green.

Ammonium Excess - Plants prefer nitrogen in the nitrate form rather than the ammonium form. In the case of plants growing in soil it is not important in which form the nitrogen is applied as there are usually bacteria present which will convert the ammonium-type nitrogen to nitrate-type nitrogen. In hydroponic systems these bacteria may not be present, hence ammonium toxicity symptoms of root damage and plant collapse may occur.

Potassium (Chemical symbol: K)

Potassium acts a catalyst within plants activating or triggering a number of plant functions. It is a catalyst for enzymes within plants that ward off disease and plays an important part in cell growth.

A deficiency in potassium can be evidenced by the mottling of older leaves on plants and a yellowing of leaves between their veins. It is another element that is mobile in the plant so the older leaves will show up any deficiency first. Plants lacking in this nutrient are liable to lose their fruit before it ripens.

Potassium Deficiency - Plants stop growing. Oldest leaves develop burnt tips and margins, and/or inter-vein yellowing.

Phosphorus (Chemical symbol: P)

Another important element for plant growth, phosphorus, is also vital for photosynthesis and cell formation in plants. It acts as a catalyst making it easier for the plant to transfer energy. Phosphorus is important in developing good root systems and is also needed for the formation of a plantís flowers and seeds. Because phosphorus is very mobile within the plant, like nitrogen, any deficiency is usually visible in the colour of the plantís leaves. Phosphorus deficiency produces a deep green leaf colouring.

Phosphorus Deficiency - Plants stop growing and become dark green, often with a purple tinge. Later the lower leaves turn yellow and fall off.

Calcium (Chemical symbol: Ca)

Calcium is the element which supports the cell walls in plants as they form. It helps to buffer the excesses of other elements and is an important part of a plantís root structure. Calcium is not very mobile in plants so it is present in greater concentration in older growth. As a result it is the new growth that suffers first when there is a calcium deficiency. The older growth retains its calcium but the new growth will be short of this important element. The new leaf tips and growing points ten to die back with a deficiency of calcium and the leaves show a brown to black scorching.

Calcium Deficiency - Symptoms develop rapidly and first appear as tip necrosis on the new emerging leaves. As these leaves expand to full size, they become more severe and the growing points die. Root growth is also affected.

Magnesium (Chemical symbol Mg)

Magnesium is another element that is important for photosynthesis in plants. It is vital to the chlorophyll molecule and is also used extensively in the production of seeds. A deficiency will produce yellowing in a plantís leaves, spreading from the centre to the outer edges of the leaf. Eventually the leaves will turn an orange colour.

A shortage of magnesium produces further problems if you want to propagate further plants from the seed being produced as they will be malformed and will have a low rate of germination. Magnesium acts as a carrier of phosphorus within the plant and promotes the formation of oils, fats and juice.

Magnesium Deficiency - Usually first appears on old to middle aged leaves as an inter-vein chlorosis (yellowing). Some plants will develop a reddening around the leaf margin (e.g. subterranean clover). The base of the leaf around the mid-vein often remains green.

Sulphur (Chemical symbol S)

Sulphur (Chemical symbol S) Sulphur is important in a plantís tissue structure, like calcium. It is one of the components of plant proteins and plays an important part in producing the flavours and odours in most plants.

A lack of sulphur shows up when the younger leaves on a plant become pale. Although growth will continue, it tends to be hard and woody with very little increase in radial growth. Sulphur does not move around much within a plant.

Iron (Chemical symbol: Fe)

Iron is necessary for the production of chlorophyll in plants and is used in photosynthesis. A deficiency of iron will affect the plantís new growth, the leaves will become almost white and the leaf veins show a definite yellowing. Iron is not very mobile within plants or easily absorbed by them, making it a difficult element to replace once lost. Iron is an essential micronutrient required by all plants and animals.

Iron Deficiency - Affects the youngest leaves on the plants. A mild symptom is an inter-vein yellowing on the youngest leaves. As the plants become more severely deficient in iron, the new growth will be entirely yellow to white in colour, with burning around the edges.

Manganese (Chemical symbol: Mn)

Manganese is involved with many enzymes in plants, especially those that reduce nitrates prior to the production of proteins. Generally a shortage of manganese will be characterised by the mottled yellowing of younger leaves. On citrus trees especially, only small yellow leaves form and do not develop any further. The formation of new bloom buds is also affected.

Manganese Deficiency - Symptoms appear on the youngest leaves of the plant usually as an inter-vein yellowing. In some plants inter-vein necrotic spotting occurs.

Boron (Chemical symbol B)

Deficiency in this element is generally shown by the slow death of plant tissue, especially around the main growing point and apex or centre point of the roots. Cracks varying in size from small to quite large appear on the fruit of plants lacking in boron. Quite often the stems deteriorate and become hollow. Boron is necessary for normal cell division and protein formation as well as being important for pollination and seed production.

Boron Deficiency - This affects the youngest tissue. Leaves yellow with necrosis and frequently become very brittle and distorted. Growing points die.

Zinc (Chemical symbol: Zn)

Zinc is an element involved in the growth hormones and is also important for most plant enzymes. Zinc is another element that is not easily replaced once lost. The new leaves of plants deficient in zinc are extremely undersized.

Zinc increases the source of energy for the production of chlorophyll and also promotes the absorption of water. This is partly why plants lacking in zinc are liable to be stunted. The formation of auxins, hormones which promote growth in plant cells, is also partly dependent on the presence of zinc.

Copper (Chemical symbol: Cu)

Copper is used by plants as an activator or catalyst for several important enzymes. A lack of copper will result in the wilting of new growth or sometimes irregular growth, often with new shoots dying back. Fruit will often split while it is ripening, especially in warm temperatures. Copper increases the sugar content of citrus fruit and intensifies the colour of crops such as carrots, spinach and apples. Copper is important in the utilisation of iron when haemoglobin is formed in the blood of animals.

Molybdenum (Chemical symbol Mo)

Molybdenum is used in the formation of proteins by plants and affects the plantís ability to fix atmospheric nitrogen. A deficiency may be indicated by pale leaves which appear burnt towards the edges. The foliage may also become distorted. Broccoli, Brussel sprouts, cabbage, cauliflowers and other brassicas will not develop leaves properly when there is a shortage of molybdenum. Molybdenum is also essential for plants such as peas which have nodules on their roots for nitrogen fixing bacteria. †