Authors: Ruth Sorenson, Extension Technician, and Diane Relf, Extension Specialist, Horticulture, Virginia Tech
Publication Number 426-084, July 1996
Introduction |
Plant Requirements |
Types of Systems |
Summary |
Nutrient Deficiencies |
Suggested Reading |
Growers all over the world are using hydroponic techniques due to the lack of a large water supply or fertile farmland. Home gardeners have used hydroponics on a smaller scale to grow fresh vegetables year round and to grow plants in smaller spaces, such as an apartment or balcony. Greenhouses and nurseries grow their plants in a soilless, peat- or bark-based growing mix. The nutrients then are applied to the growing mix through the water supply. Therefore, this is also a type of hydroponics.
Soilless gardening offers many advantages to the home gardener. Since a sterile medium is used, there are no weeds to remove, and soil-borne pests and diseases are minimized, if not eliminated completely. Properly grown hydroponic plants also are healthier and more vigorous because all of the necessary growth elements are readily available. The plants can mature faster, yielding an earlier harvest of vegetable and flower crops. Hydroponic gardens use less space since the roots do not have to spread out in search of food and water. This small space requirement makes hydroponics ideal for home gardeners, and it makes better use of greenhouse space. The big advantage to hydroponics is the ability to automate the entire system with a timer. Automation reduces the actual time it takes to maintain plant growth requirements. Automation also provides flexibility to the gardener as one can be gone for long periods of time without having to worry about watering the plants.
Hydroponics offers many advantages for commercial agriculture. Cultivating plants without soil eliminates the need for vast farmland and allows crops to be produced in greenhouses or even in the desert sands. Hydroponic techniques also allow for precise water and nutrient application directly to the roots of each plant. Water is reused in these systems and less is lost through evaporation and run-off. Therefore, arid lands, such as deserts, can be transformed into productive lands using limited amounts of water. Growing plants hydroponically is not difficult if one understands the basic principles. As long as plant growth requirements are met, there are numerous hydroponic systems that can be used.
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Depending on the stage of plant development, some elements in the nutrient solution will be depleted more quickly than others. Because of this, it is important to change the nutrient solution every two weeks. The old solution can be used to water other houseplants or outdoor plants. Also, make sure that the nutrient solution is kept at the original volume. As water evaporates from the nutrient solution, the fertilizer becomes more concentrated and can burn plant roots. Add water only and not more fertilizer to raise the nutrient solution back to its original volume.
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The nutrient film technique (Figure 1) uses a plastic trough or tube as the container through which a constant, thin film of nutrient solution flows. Plants are suspended through holes in the top of the trough. The trough is gently sloped so gravity pulls the solution back to the nutrient reservoir. There are many variations of this system, making it the most popular for the home gardener.
Aeroponics (Figure 2) is the growing of plants in a container in which the roots are suspended in a nutrient mist rather than in a solution. The most popular container for aeroponics is an enclosed A-frame constructed of styrofoam boards. The plants are placed in holes along the sloped sides of the frame. The nutrient mist is delivered to the roots by a vaporizer or by special attachments available with drip irrigation kits. The mist clings to the roots. Any excess runs down the inside of the frame, is collected at the bottom, and is recycled back to the nutrient reservoir.
The aeration method (Figure 3), one of the first systems to be developed, uses an aquarium air pump to bubble oxygen to the roots of plants immersed in the nutrient solution. Plants are suspended 1 inch above the solution by a 2-inch-deep mesh tray that is set into the container by placing the lip of the tray over the container's edge. A layer of inert material, such as gravel, clay pebbles, or vermiculite, is placed in the tray to provide stability for the plants while allowing the roots to grow down into the nutrient solution.
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Another common aggregate system is the trickle feed method (Figure 5). The nutrient solution is continuously pumped from the reservoir through a 1/2-inch irrigation tube that branches into a number of 1/8-inch tubes. These smaller tubes deliver the solution to the containers. Any excess solution is collected at the base of each container and returned to the nutrient reservoir.
A modification of the trickle feed method is called tube culture (Figure 6). A 4- to 6-inch plastic tube or bag is filled with a lightweight aggregate. Holes are made on all sides of the container for the plants. The tube is hung vertically, and an irrigation tube is positioned at the top of the container. The nutrient solution seeps through the container and may or may not be recycled when it reaches the bottom.
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Hydroponic systems are available in a variety of sizes and prices. Kits are available from many suppliers, and some hydroponic systems can be built easily at home from materials found at hardware stores and fish supply stores. Numerous hydroponic and soilless gardening books can be found in local libraries and bookstores. Information also is available through the Hydroponic Society of America, P.O. Box 6067, Concord, CA 94524, (415)682-4193.
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Occasionally, the nutrients in a hydroponic system are used up faster than they can be replaced, and the plants will show a nutrient deficiency. A quick fix for most of the deficiencies is to spray the leaves with an all-purpose, foliar fertilizer, although this will not completely solve the problem. The best remedy is to change the nutrient solution every week instead of every two weeks. In some cases, it may be necessary to switch to a different type of hydroponic fertilizer, if the same deficiencies persist. There are several books on hydroponics that give other remedies for a nutrient deficiency problem.
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Home Hydroponics...and how to do it!, Lem Jones, New York, N.Y.: Crown Publishers, Inc., 1977.
Hydroponic Food Production, 4th ed., Dr. Howard Resh, Santa Barbara, Calif.: Woodbridge Press, 1989.
Hydroponics for the Home Gardener, Stewart Kenyon, Toronto, Ont., Canada: Van Nostrand Reinhold Ltd., 1979.
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