growing of plants without soil in water to which nutrients have been added. Hydroponics has been used for over a century as a research technique, but not until 1929 were experiments conducted solely to determine its feasibility for growing commercial crops. There are now hydroponic home gardens and commercial cropping operations in the United States and many other countries. Under hydroponics, plants can be grown closer together than in the field, thereby increasing yields, and multiple cropping (the growing of several crops in the same tank) can be practiced. In addition to conserving space, hydroponics almost eliminates weed and pest problems, and can use significantly less water than may be needed for irrigation when crops are grown in fields (an advantage where water is scarce). The cost of equipment is high and personnel must be trained. Although hydroponics is possible for most plant species, a limiting factor is the amount of physical support required. Usually the plants are held upright by wire supports or are rooted in a sterile medium, e.g., pure sand or gravel. The nutrient solutions must supply, in optimum concentrations and in correct balance, the elements, such as nitrogen, phosphorus, potassium, and other essential nutrients normally found in soil. Other names for hydroponics are soilless gardening, soilless culture, chemiculture, and water gardening. Aquaponics
See R. Bridwell, Hydroponic Gardening (rev. ed. 1990); R. E. Nicholls, Beginning Hydroponics (1990).
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