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Three major fertilizers needed.
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The minor chemicals needed.
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The nutrient solution is the basis of hydroponics. Even very poor soil has some nutrient content, otherwise plants would not grow in it. Hydroponic media contain no nutrient whatsoever, so you must supply the plant with everything it needs, i.e., nutrient and sunlight. Along with carbon, hydrogen and oxygen, which plants obtain from air and water, plants need thirteen mineral elements to thrive. If one is missing, results will be disappointing. It is convenient to divide these elements into two groups .. Major Elements and Minor elements.

Major Elements:
These are Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg) and Sulphur (S).

Nitrogen:
Nitrogen is essential for many plant functions. Insufficient nitrogen will give leaves that are yellowish and pale with poor growth. Too much nitrogen usually gives abundant foliage growth, but poor fruiting. Gardeners recognise nitrogen as being available in two forms .. ammonia-type nitrogen and nitrate-type nitrogen. Most plants prefer to obtain their nitrogen in the nitrate form. Urea and Sulphate of Ammonia are unsuitable for hydroponics as they need to undergo conversion from ammonia-type to nitrate-type by soil bacteria before plants can use them. In sunny climates, plants need more nitrogen than the same plants in a cooler climate. Plants such as lettuce, cabbage and silverbeet generally need more nitrogen than less leafy plants. The most popular nitrate-type fertilizers are Potassium Nitrate and Calcium Nitrate, both of which feature in the Starting Formula on the next page.

Phosphorus:
Phosphorus is important for the fruit producing vegetables such as peas and beans. A deficiency usually manifests itself as a dark or purplish colouration in the leaves. Phosphorus is also important for good root growth. Australian soils are notoriously deficient in phosphorus, and many native plants can get by without it. The Starting Formula on the next page gets its phosphorus from Mono Ammonium Phosphate, which, unlike the very popular Superphosphate, is entirely soluble in water.

Potassium:
Potassium is essential for good fruit setting and development. Plants in cooler climates need more potassium than the same plants in hot, sunny climates. A potassium deficiency will generally show up as a mottling of the lower leaves, followed by scorching of the outer leaf margins which eventually extends to the whole leaf. The potassium in the Starting Formula, on the next page, is supplied by Potassium Nitrate.

Calcium:
Calcium is necessary for good root growth. A deficiency of calcium usually shows up as a dark, stunted growth usually with crinkled leaves. Calcium Nitrate supplies this needed element in the Starting Formula, on the next page.

Magnesium:
Magnesium is at the centre of the chlorophyl molecule, and plants need surprising quantities of it. A deficiency shows up in pale, yellowish leaves, usually starting from the base. Flowering may also be slow. The Starting Formula, on the next page, gets its magnesium from Epsom's Salts (Magnesium Sulphate).

Sulphur:
Sulphur is supplied by Magnesium Sulphate. A deficiency usually gives leaves a yellowish appearance and are often purple at the base.

Minor Elements:
These are Iron (Fe), Boron (B), Manganese (Mn), Zinc (Zn), Copper (Cu), Molybdenum (Mo) and Chlorine (Cl).

Iron:
Iron, in the inorganic form (e.g. as Iron Sulphate) when added to alkaline solutions (high in pH), precipatates out completely leaving no iron in solution. It is for this reason iron for hydroponic nutrient solutions is best supplied in an organic form such as Iron-EDTA. (The iron salt of Ethylene Di-Amine Tetra Acetic Acid). A deficiency of iron has a drastic effect on plants. There will be little or no growth, accompanied by acute yellowing and leaf scorch. The Starting Formula on the next page derives its iron from Iron-EDTA.

Boron:
Boron is necessary as a trace element to eliminate several undesirable features in vegetables, such as brittle stems, dying growing tips, and hollow stemmed cauliflowers. Boron is supplied in the Starting Formula by Borax, otherwise known as Sodium Tetra Borate.

Manganese:
Manganese is required in trace quantities in hydroponic nutrient solutions. A deficiency of manganese is similar to a deficiency of magnesium, except that pale and yellowish leaves are observed at the top rather than the bottom of the leaf. The Starting Formula gets its manganese from Manganese Sulphate.

Zinc:
Zinc is another element needed in trace quantities. These trace elements act as chemical catalysts, assisting other elements to do their job. Zinc Sulphate is used in the Starting Formula as a source of zinc.

Copper:
Copper Sulphate supplies this trace element for the Starting Formula. Copper is another catalyst necessary for plant life on Earth.

Molybdenum:
A deficiency of this trace element causes "whip-tail" in cauliflowers, and "blossom end rot" in tomatoes. The fully soluble salt, Ammonium Molybdate supplies molybdenum to the Starting Formula.

Chlorine:
Chlorine is a trace element that catalyses other reactions. Water supplies generally contain sufficient chlorine to do the job without adding a few specks of ordinary cooking salt.

Silicon:
Recent research tends to suggest that plants need Silicon as a trace element as well. It is thought to have an influence on the strength of the cell wall. A suitable source of soluble silicon is Sodium Silicate, sold as "Waterglass" for preserving eggs. The usage quantity would be only a few drops.

The next page shows a suggested Starting Formula.

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