Although commercial hydroponic systems are designed for a greenhouse, hobbyists may set up a small system on a patio, on a rooftop, or in the yard. Plants grown in an outdoor system should be started on the same dates as recommended for gardens (see Illinois Cooperative Extension Service Circular 1150, Vegetable Gardening for Illinois).

Seed Germination

Large seeds can be planted directly into aggregate culture systems or devices such as the Pipe Dream and thinned later. Plants with small seeds should be transplanted into the system to insure a good stand. With the water culture method, all plants must be transplanted to the system.

Seedlings to be transferred can be grown with their roots exposed or in root cubes. It is best to grow them with exposed roots if they are to be grown in a water culture or aeroponic system. Sow the seeds in quartz sand, coarse vermiculite, or perlite. Water them and cover them with wet paper towels or cheesecloth until they germinate. Then remove the covering and thin the plants. Moisten them as needed with a dilute nutrient solution rather than water because the germination medium does not provide adequate nutrition. A one-fourth concentration of the nutrient solution recommended in the next section may be used. When the seedlings are large enough to transplant, gently wash the growing medium from their roots. Do not be concerned if a few pieces of the medium remain on the roots.

Seedlings for the PVC pipe or NFT system should be grown in sterile root cubes, which are composed of expanded plastic foam, cellulose fiber, or a compressed mixture of peat and vermiculite. These cubes provide weight and help support the plant in the tube. Peat-lite mix or peat pots should not be used as they will disintegrate, and the particles may clog the pump that circulates the nutrient solution. Oasis Rootcubes and Horticubes are examples of commercially available root cubes.

Nutrient Solutions

Premixed nutrient solutions are available from a number of sources. They are relatively inexpensive and easy to use. As you become more familiar with growing plants hydroponically you may wish to make your own nutrient solutions. You may find it interesting to observe the effects of varying the nutrient concentrations and to produce specific deficiency symptoms by omitting one nutrient. The effects of changing the total nutrient concentration or the solution pH are also interesting.

The nutrient solution given on the next page, developed by D. R. Hoagland at the University of California, can be made up from readily available salts and will supply the major elements (macronutrients) needed for plant growth. It is easy to prepare and usually gives satisfactory results.

Salt Amount for 25 gallons
of solution
Potassium phosphate - monobasic (KH2PO4) 1/2 ounce or 1 teaspoon
Potassium nitrate (KNO3) 2 ounces or 4 teaspoons of powdered salt
Calcium nitrate (CaNO3) 3 ounces or 7 teaspoons
Magnesium sulfate (MgSO4) 1 1/2 ounces or 4 teaspoons

The salts should be dissolved in warm water separately and then added to the solution tank. Reagent or chemical grade potassium phosphate and magnesium sulfate are recommended. Fertilizer grade potassium nitrate and calcium nitrate may be used and are less expensive than the chemically pure forms.

Micronutrients are needed in extremely small amounts. Because it is difficult to weigh out such small quantities, stock solutions of dilute micronutrients should be made up and added to the solution tank. Use only reagent grade chemicals, which are usually available in hobby shops.

Chemical Amount for 1 gallon
of stock solution
Amount of stock solution
for 25 gallons
of nutrient solution
Boric Acid
2 teaspoons 1/2 pint
Manganese chloride
(MnCl2 . 4H2O)
1 teaspoon 1/2 pint
Zinc sulfate
(ZnSO4 . 7H2O)
2 teaspoons 1/2 teaspoon
Copper sulfate
(CuSO4 . 5H2O)
1 teaspoon 1/2 teaspoon
Iron sulfate
(FeSO4 . 7H2O)
4 teaspoons 1/2 pint

If tap water is used, zinc sulfate and copper sulfate may not be required. The small amounts of zinc and sulfur needed are usually present in the water or as an impurity in the other fertilizer nutrients.
An iron chelate should be substituted for the iron sulfate if your tap water is alkaline. Mix 1 1/2 ounces of NaFe EDTA (13 percent Fe203) in 5 quarts of water. Use l/4 pint of this solution for 25 gallons of stock solution. For other chelate products calculate the amount required to result in a final nutrient solution containing 1 part per million of elemental iron.

As the plants take up nutrients they will release chemicals into the solution that may cause it to become more alkaline. When the pH rises above 7.0 add enough sulfuric acid (battery acid) to bring it back to a pH between 5.5 and 6.5. For large plants it may be necessary to add acid daily. If the solution becomes acidic, the pH can be raised with potassium hydroxide (KOH) or sodium hydroxide (NaOH). A variety of pH meters and testing kits are available for checking pH levels.

The nutrient solution should be changed once every two weeks when the plants are small and once a week as the plants begin to grow rapidly. Add water daily to keep the amount of solution constant.

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