The possibility that plants could survive and grow without soil as the nutrient source was first described historically by Woodward in 1699. In the 1840's, a number of German botanists developed the basic nutrient formulas and growing techniques which are in use today. Most of what has been developed since then are refinements of and adaptations to these early discoveries. Hydroponics requires as little as 10% as much land as regular farming, and less than 10% as much water. If the hydroponic water is recirculated, water use is dramatically less. Hydroponic advocates claims that an area the size of a large back yard can supply 100 people with fresh vegetables during the year. Hydroponic produce is less affected by insects so does not carry traces of insecticide, and can be picked ripe just before eating so preservatives are not required. Produce such as broccoli, cabbage, celery, chard, cucumbers, eggplant, flowers, grapes, lettuce, melons, onions, peppers, pole beans, radishes, strawberries, and tomatoes have been grown hydroponically.
An article called Feeding Astronauts - And Ourselves on page 40 of the Jan/Feb '92 issue of The Futurist magazine describes the benefits to be derived from hydroponics. Excerpts of the article follow:
[Hydroponics is] an agricultural technique that uses nutrient-enriched water rather than soil as a growth medium. ... Growth chambers allow the producer to control the amount of light and carbon dioxide the plants receive, as well as the humidity and temperature of the air. Because there are no seasons inside a growth chamber, crops could grow year-round in any part of the world, eliminating transportation and storage costs. In addition, herbicides and insecticides are unnecessary because there are no weeds or insects to disturb the plants.
An article called Hydroponic Produce on page 8 of the July '91 issue of Consumer Research magazine describes hydroponic techniques and the variety of vegetables, fruits, and flowers that are being successfully grown hydroponically. Excerpts of the article follow:
Hydroponically-grown vegetables such as tomatoes, "burpless" cucumbers, and bibb lettuce have become commonplace offerings in the produce sections of many supermarkets. Many consumers favor these vegetables, which, being grown in water, are clean and have no soil clinging to them. Such produce has good flavor, having been allowed to ripen fully before it is picked. Because the roots of bibb lettuce are left intact on the plant within the plastic wrapper, the lettuce actually continues to grow and does not wilt readily. The controlled environment of hydroponics also eliminates the need for pesticides.
Modern hydroponics began in the 1860s. Plants were found to thrive, provided they received all the needed macro and micro nutrients from inorganic salts in solutions. Water economy is an attractive feature for arid areas because, in hydroponic systems, precious water can be recirculated. A large volume of hydroponic food can be grown rapidly in a small area. Reportedly, four heads of lettuce can be raised in the same amount of space required to grow one head of field lettuce. ... The technique has been suggested to raise a weekly crop of grass as cattle feed.
Hydroponic techniques vary. In water culture, the roots of the plants are held in a large waterproof tank. The plants are supported by mesh or string. In gravel cultures - a more costly system to install and maintain - a water-proof bench is filled with inert pea-sized gravel to support the roots. A solution containing all the essential nutrients required by the plant is pumped into the gravel from a holding tank. When the bench is full of the solution, the pump is turned off and the solution drains back to the holding tank. The solution is replenished periodically. A nutrient film technique is another system, which does not required as large a holding tank as that used in gravel culture. The plants grow in narrow, shallow troughs, and the roots of the plants are constantly bathed in a flowing solution of nutrients.
The lamps that are used emit three different wavelengths of light (red, far red, and blue) in a proper ratio to stimulate photosynthesis.