HYDROPONIC INFORMATION

NUTRIENTS

Many commercial hydroponic growers use a nutrient formula that is designed for growing only one type of plant. These growers will also use a separate hydroponic nutrient formula for each of the 3 different stages of the plant’s growth which are the early growing stage, the flower stage and the fruiting (or bloom) stage. These three different nutrient formulae maximizes a crop’s yield and commercial farmers need every extra increase in crop yields they can achieve to help maintain a healthy profit margin.
Most home gardeners grow a variety of vegetables and plants and most of these would be at different stages of growth. It would be very complicated and expensive for a home gardener to use a 3 stage hydroponic nutrient formula in their small gardens. You would need at least 3 nutrient solution holding tanks just for your tomatoes and eggplants and then some more holding tanks for your lettuces and herbs. A well balanced, general purpose hydroponic nutrient formula will make gardening simpler, less expensive and more enjoyable. Your crop yields will still be high.

NUTRIENT ELEMENTS

There are 14 nutrients required by a plant for lush, healthy growth. These are carbon, hydrogen and oxygen which are obtained from the air and water. A plant also needs nitrogen, phosphorous, potassium, sulphur, magnesium, calcium, iron, copper, zinc, boron and molybdenum all in the right balance. If these nutrients are not in balance then the plants will be severely affected and even die. Refer to Why is my plant sick?

NITROGEN

Nitrogen is needed for the production of chlorophyll and plant protein molecules. It is one of the most important elements involved in plant growth and crop yields. However, a mixture of ammonium nitrate and other nitrates will significantly decrease yields according to horticulture research.
Nitrogen deficiency causes plants to be spindly with small yellowish leaves. Parts of the plant will turn purple and then the plant becomes pale and yellow esp. the older leaves. The new leaves in tomato plants point vertical. The stems are short and the leaves and fruit are small.
Nitrogen excess results in dark green plants with abundant foliage but the flowering and fruiting are delayed. There is stunted root growth. Flower drop occurs resulting in little fruit production.
Nitrogen rich salts are ammonium nitrate, calcium nitrate, potassium nitrate, ammonium sulphate and urea (not to be used in hydroponics)

PHOSPHORUS

Phosphorous is important for photosynthesis and respiration and is also involved in energy transfer and storage. Phosphorous is also needed for protein and root production and cellular division.
Phosphorus excess causes leaves to be bright brown or yellow brown in colour, similar to a nitrogen deficiency. Mature leaves appear crushed. Leaves and fruit develop areas of bright dry spots. Fruit will ripen earlier. Affects the availability of copper and zinc and may cause deficiencies in these nutrients.
Phosphorus deficiencies will cause leaves to have a distinct purple tint under young leaves. Stems and petioles will have a purplish tinge. The leaves will also curl backward and wilt. Phosphorus also affects growing tips and lateral shoots causing slow plant growth resulting in small plants. The plants maturity is delayed and fruiting is poor. The roots are stunted and yellow brown. Phosphorous deficiency can occur during cold temperatures, particular during cold nights.
Common phosphorus salts are ammonium hydrogen phosphates, potassium hydrogen phosphates, calcium phosphates and super phosphates (not for hydroponics).

POTASSIUM

Potassium is very important for a plant and has many functions. These are:
Transportation of sugars. Stomata control. Transpiration. Metabolism of carbohydrates and proteins.
Activates enzymes. Regulates osmotic pressure. Increases sugar content in fruit. Improves taste.
Increases turgor (firmness) in stems and fruit.  Improves wilting resistance. pH control.
Reduces susceptibility to plant diseases such as rusts and moulds. Salt and water uptake.
Balancing of negative electrical charges in the plant.
Potassium excess causes young leaves to turn a bright green and mature leaves become yellow. Leaf stalks become hard and brittle. Potassium is not usually absorbed by plants in excessive amounts, but high levels may also lead to deficiencies in magnesium, manganese, iron and zinc.
Potassium deficiency initially causes yellowing and burning on leaf margins (edges) of young leaves progressing to increase yellowing of leaves between the veins. The veins remain green. Older leaves will have brown mottling and will curl and crinkle. Potassium deficiency results in poor growth, small leaves, soft stems and young leaves drooping. Flowers are fewer, pale and lack brilliance. Roots develop a yellow brown colour. Plant is prone to fungus.
Fruit will ripen blotchy and boxy. A foliar spray of 2% potassium sulphate may help.
Common potassium salts are potassium nitrate, potassium sulphate, potassium chloride, potassium phosphate.

CALCIUM

Calcium is an essential ingredient of cell walls and plant structure and growth. It buffers the effects of excesses of other elements. It prolongs the life of a leaf. It is also important for the development of root nodules in legumes. It is also the main element responsible for fruit firmness.
Calcium excess reduces the absorption of potassium, magnesium and trace elements and gives the effect that there are deficiencies of these elements. Older leaves may develop spots between veins.
Calcium deficiencyA calcium deficiency will affect young tissues first. Growing tips and young leaves become stunted, turn yellow on the leaf margins at first and die. Underside of leaf turns purple and leaf curls. Root growth is stunted. Flowering fails and fruit will get brown spots first and then progress to blossom end rot (or BER Syndrome), esp. tomatoes. Hot weather accentuates this decay.
Calcium deficiency will also make plants more susceptible to heat stress. In most cases the Calcium deficiency is caused is  by water stress on the plant, large variations in humidity and high levels of calcium salts.
Foliar sprays of 0.75% to 1 % calcium nitrate solution may help.
Common calcium salts are calcium nitrate, calcium chloride, calcium phosphate, calcium sulphates (gypsum) calcium carbonate, lime and superphosphate.

MAGNESIUM

Magnesium plays an important role in photosynthesis as it is an significant component of chlorophyll. It is also a component in enzymes and helps plants utilize phosphorus.
Magnesium excess results in a cut and ragged appearance of mature leaves. The older leaves and fruit develop bright dry spots.
Magnesium deficiency results in leaves first turning yellow at the leaf edges, then progressively yellowing towards the centre until a green arrow shape forms. Only the youngest leaves remain green. Older leaves become mottled.  Brown dead areas form. Flowering is decreased but rarely results in yield reduction. High potassium levels can limit the uptake of magnesium. .In its advanced form, magnesium deficiency may superficially resemble potassium deficiency.
The deficiency is corrected by watering with a 10 % magnesium sulphate solution.
Common magnesium salts are magnesium sulphate (Epsom salts), magnesium chloride, dolomite and magnesium nitrate.

SULPHUR

Plants can only absorb sulphur as sulphate ions.
Sulphur is a significant component of some amino acids and proteins. It is also involved in the production of carbohydrates, proteins and lipids. Sulphur is needed by plants to produce their perfume, flavour and odour.
Sulphur excess causes small leaves and slow growth in plants. Root systems become harder and more compact.
Sulphur deficiency is not very common. Plants are stunted and young leaves turn yellow. A reddish to purple colour may form at the leaf base under the leaves. The upper leaves become stiff and curl downward. The stems, veins, and petioles turn purple. Sulphur deficiency resembles nitrogen deficiency but in sulphur deficiency the yellowing is much more uniform over the entire plant including young leaves Protein production is reduced. Root systems become larger and softer.
Common sulphur salts are sodium sulphate, calcium sulphate, ammonium sulphate, and ferrous sulphate.

IRON

Iron has an important role in photosynthesis as well as nitrogen fixation in legumes, reduction of nitrates and in the production of some enzymes..
Iron excess slows plant growth.
Iron deficiency impacts a plant quickly but is not a common problem. The symptoms are similar to a plant not exposed to light. Young plants turn almost white. The veins in older leaves first turn yellow and then the whole leaf will turn yellow and die. Blossom drop occurs and root systems may turn a yellow brown.
If the pH is too alkaline iron may become insoluble and drop out of the solution. If the pH is too low plants will uptake aluminium, restricting iron absorption. An iron deficiency may also be caused by an excess of manganese, copper or zinc
A foliar spray of 0.5% iron chelate every 3 to 4 days with restore the coloured leaves to normal. The veins in the leaves will be the first to change green.
Common iron salts are ferrous sulphate, ferric chloride, and iron chelates.

MANGANESE

Manganese is important for photosynthesis, carbohydrate metabolism, oxidation processes, the activation of certain enzymes and the reduction of nitrate to amino acids and proteins.
Manganese excess causes the leaves to become bright brown or yellow brown and may affect the availability of iron. The toxic level for manganese is 500 ppm.
Manganese deficiency causes leaves to have a cut and ragged appearance. Young plants turn mottled yellow colour. As the deficiency increases, the leaves take on a grey to purplish metallic sheen and develop dark freckled and dead areas along the veins.
Plant growth is stunted. Flower buds fail to bloom. Fruit production is small and the fruit develops spots.
Foliar spray using 1 % solution of manganese sulphate is one remedy.
Common salts are manganese sulphate and manganese chloride.

BORON

The concentration of this trace element is very critical.
Boron is closely related to the functions of calcium. It is important in the movement of sugars, germination, cell wall structure, and the formation of cell wall.
Boron excess results in the leaves having dry margins and a cut and ragged appearance. Boron is an essential plant nutrient but when it exceeds 150 ppm it becomes toxic.
Boron deficiency causes the leaf tips to yellow, then become highly coloured and defoliate. The stems become brittle. The core of the plant develops a cork like appearance and brown spots. Boron deficiency symptoms generally appear in younger plants at the propagation stage. The growing points wither and die and the growth of the plant slows down and stops. Pollen formation is poor and this results in poor fertilization of flowers. The fruit is often split and miss-shaped. Boron deficiency can lead to calcium deficiency.
Foliar spray of 0.1 to 0.25% borax is needed.
Common boron salts are boric acid and borax.

ZINC

Zinc is important for nitrogen metabolism, respiration and the development of growth hormones including auxins.
Zinc  excess may affect the availability of iron. Toxic level for Zinc is 300 ppm.
Zinc Deficiency causes the younger leaves to become yellow with very small leaves in the early stage of zinc deficiency.  Maturity is delayed and the stems of the plant fail to elongate resulting in rosetting of the leaves. As the deficiency progresses dead areas and pitting form on the older leaves but the main veins remain green.
Excess phosphorus may cause a zinc deficiency.
A foliar spray with 0.1 to 0.5% solution of zinc sulphate is needed.
Common zinc salts are zinc sulphate and zinc chloride.

COPPER

Copper is present in fairly high concentrations in the chloroplasts of the plant. It activates a number of essential plant growth hormones and influences the metabolism of nitrogen and carbohydrates
Copper excess causes chlorosis (yellowing) of the leaves and defoliation. Roots develop a black colour.
Copper deficiency causes die back. Young leaves become misshapen, curling into a tube. Leaves become pale yellow and spotted. Young tips and buds will wilt and die. Plant growth is irregular and reduced with few or no flowers. Excess phosphorus may cause a copper deficiency.
Use a foliar spray with 0.1 to 0.2% solution of copper sulphate to which 0.5% hydrated lime has been added.
The most common copper salt used is copper sulphate.

MOLYBDENUM

Molybdenum is a minute trace element but essential for plant growth. It reduces nitrates prior to the formation of proteins and is a component of some enzymes.
Molybdenum excess will turn leaves a brilliant orange at high concentrations. It causes tomato leaves to become bright yellow.
Molybdenum deficiency causes symptoms similar to nitrogen deficiency without the reddish coloration on the undersides of the leaves. Nitrates accumulate in the plant that cannot be used. An early symptom for molybdenum deficiency is a general overall yellowing. The leaves become small and yellowish. Yellowing forms between the leaf veins in older leaves. Tomato leaves turn golden yellow. The leaf margins dry out and burn. The edges of leaves curl up upward. Plants become pale.
Use a foliar spray with 0.07 to 0.1% solution of ammonium or sodium molybdite
Common molybdenum salts are ammonium molybdite and sodium molybdite.

pH

The pH of a solution is a measure of how acidic a solution is. A number rating of 1 to 14 is used where 1 is very acidic, to 7 which is neutral, to 14 which is very basic. Unless you are a large commercial grower, the pH of your nutrient solution is usually not an issue if you have a well-balanced nutrient solution for a home hydroponic setup.
The ideal pH for growing plants in a hydroponic system is between 5.5 and 6.5. If the pH moves out of this range it is an indication that something may be wrong somewhere, mainly for the large commercial farms, and needs investigating. They have a great deal to lose if their crops fail, even in quality. A lower pH needs to be adjusted quickly as some of the trace elements, such as iron, will drop out of solution which will deprive the plants of that nutrient.
If you want to monitor the pH of your nutrients there are cheap pH indicator papers that will cover this range adequately or you can buy a more expensive electronic monitor that will need calibrating each time. There are other cheaper but less accurate monitors that will also be good enough for a home gardener. Chemical indicators also work well. You will need to monitor the pH of your nutrients before the nutrient solution enters your hydroponic system, within the system and after the nutrient solution leave as excess.
The pH readings can only tell you whether the cations or anions of your nutrients are in excess, which could indicate that your hydroponic nutrients may not be balanced. Commercial growers will regularly have their nutrients tested in a laboratory to find out exactly which nutrients are not being used by the plant. I monitor my nutrients for pH levels and I have never had a reading outside of the optimum range so far.

SALINITY

I have only had a problem with salinity before I made my own hydroponic nutrients. The salinity readings from the excess nutrients were much higher than in the nutrient solution I was putting in. This meant that at least one or maybe more of the nutrients were not being absorbed by the plant and were building up. I was buying my nutrients at the time and this indicated that the hydroponic nutrients that this company was selling were not in balance. This was confirmed when my tomatoes plants turned purple because of a deficiency of phosphorus. For more information on nutrient deficiency problems refer to Why is my plant sick?
I have a chemistry and biology career background and I looked up the research results of several horticulture universities. The nutrient balance that the universities recommended were completely different to that listed in the hydroponic nutrient solution I was buying. This motivated me to make my own hydroponic nutrients based on the data from these universities and it works very well. It is difficult to find well balanced  hydroponic nutrients designed for vegetables for sale on the market so I have begun selling my own brand to help other home gardeners using a hydroponic system.
All of the hydroponic nutrients are in a salt form. The salinity readings are more useful than the pH readings for a gardener with a hydroponic setup at home. The readings can be in electrical conductivity units (EC) as the salinity monitor works by measuring the conductivity of the nutrients. The salinity readings can also be expressed as parts per million (ppm) as a measure of the concentration of the nutrients. A salinity monitor can only tell you the concentration of your nutrients as a whole. It does not tell you the salinity concentration of individual nutrients. This can only be done through a laboratory. As mentioned earlier, it is possible to get an approximate understanding of which nutrients are in excess or deficient by the effects this has on the growth, leaves, flowers and fruit of an affected plant.
Some plants, such as tomatoes, are heavy feeders and need a higher concentration of nutrients for optimum growth. Tomatoes need an EC. of about 2.0 which translates to about 1400 ppm of nutrients for good growth and quality fruit. Some farmers will even double this concentration for a short time to give their plants a boost and to improve the flavour but excess nutrient levels will need to be monitored closely. This may not be necessary if the hydroponic nutrients are balanced to start with. Light feeders, such as lettuce, only need half the concentration of nutrients use for tomatoes for best growth.
The hydroponic nutrients that I make myself are based on several horticulture universities recommendations and have a nutrient EC concentration of 2.0 and a pH of 6.2. This is ideal for tomatoes, capsicums and eggplants. Lettuces, herbs and other leafy plants will require the nutrient solution to be diluted by half. The lettuces will still grow with a full strength nutrient solution made for tomatoes but some types of lettuce may taste bitter. Excess nutrient salt levels may also occur later if the setup is not flushed regularly.

LIGHTING

The amount of sunlight a plant receives during the day can greatly influence the growth of a plant. Plants that are exposed all day to full sunlight will grow far better than plants being exposed to less sunlight. This is certainly true for plants being grown in their optimum growing season.
However, if the plants are exposed to full sunlight in the middle of a hot summer many plants will wither and die from the intense heat. To overcome this problem of overheating, a gardener can use a shade cloth to cover the plants. This is far better for a plants growth than placing the plants so that they only receive the morning light and are shaded during the hotter afternoon.

The sunflower on the right was exposed directly to sunlight all day under a shade cloth and is almost twice as large as the sunflowers exposed to only the morning light. Sunflowers have small root systems and the smaller size pots would not have affected their growth much if at all.
If you are going to protect your plant from the hot summer sun then it is better to do it under shade cloth and then remove the shade cloth in autumn when the temperature is more agreeable to the plants. There are different grades of shade cloth and its main purpose is to cool the plant by providing shade. Different areas have different heat intensity from the sun and the grade of shade cloth would need to be chosen accordingly.

WATER SUPPLY AND QUALITY

Most water supplies are suitable for hydroponic systems with a few adjustments. In most cases filtered dam, river or creek water is usually suitable for hydroponic systems but in some areas a high calcium content in the water may exist. A high calcium concentration will prevent plants from absorbing potassium which in turn will decrease the yield and quality of your vegetables. You will either have to find another water source or invest in some expensive filtering processes.
Town water will need to be left exposed to air for 24 hours to allow the chlorine to evaporate out of the water before nutrient concentrates are added.
If you are using water from your dams to make up your hydroponic solution then it is very possible your water source may contain fusarium fungus that will infect your plants with Fusarium Wilt. This begins as small dark spots on the leaves near the sand surface and gradually spreads up the plant. On tomato plants the infected leaves turn yellow and die until the whole plant eventually dies. This fungal infection will attack tomatoes, capsicums, cucumbers, melons, zucchinis, strawberries and some flowers.
To avoid infection when using filtered dam water add 6 grams of pool chlorine per 1000 litres of water and allow to sit for one day before adding nutrients.