Hydroponics

Hydroponics is the practice of growing plants in water as opposed to soil . It comes from the Greek hydro ("water") and ponos ("labor"), implying "water working." The essential macro- and micro- (trace) nutrients needed by the plants are supplied in the water.

Hydroponic methods have been used for more than 2,000 years, dating back to the Hanging Gardens of Babylon. More recently, it has been used by plant physiologists to discover which nutrients are essential for plant growth. Unlike soil, where nutrient levels are unknown and variable, precise amounts and kinds of minerals can be added to deionized water, and removed individually, to find out their role in plant growth and development. During World War II hydroponics was used to grow vegetable crops by U.S. troops stationed on some Pacific islands.

Today, hydroponics is becoming a more popular alternative to conventional agriculture in locations with low or inaccessible sources of water or where land available for farming is scarce. For example, islands and desert areas like the American Southwest and the Middle East are prime regions for hydroponics. Plants are typically grown in greenhouses to prevent water loss. Even in temperate areas where fresh water is readily available, hydroponics can be used to grow crops in greenhouses during the winter months.

Two methods are traditionally used in hydroponics. The original technique is the water method, where plants are supported from a wire mesh or similar framework so that the roots hang into troughs which receive continuous supplies of nutrients. A recent modification is a nutrient-film technique (NFT), also called the nutrient-flow method, where the trough is lined with plastic. Water flows continuously over the roots, decreasing the stagnant boundary layer surrounding each root, and thus enhances nutrient uptake. This provides a versatile, lightweight, and inexpensive system. In the second method, plants are supported in a growing medium such as sterile sand, gravel, crushed volcanic rock, vermiculite, perlite, sawdust, peatmoss, or rice hulls. The nutrient solution is supplied from overhead or underneath holding tanks either continuously or semi-continuously using a drip method. The nutrient solution is usually not reused.

On some Caribbean Islands like St. Croix, hydroponics is being used in conjunction with intensive fish farms (e.g., tilapia) which use recirculated water (a practice is more recently known as aquaponics). This is a "win-win" situation because the nitrogenous wastes, which are toxic to the fish, are passed through large greenhouses with hydroponically-grown plants like lettuce. The plants remove the nutrients and the water is returned to the fish tanks. There is a sensitive balance between stocking density of fish and lettuce production. Too high a ratio of lettuce plants to fish results in lower lettuce production due to nutrient limitation. Too low a ratio also results in low vegetable production, but this time as a result of the buildup of toxic chemicals . The optimum yield came from a ratio of 1.9 lettuce plants to 1 fish. One pound (0.45 kg) of feed per day was appropriate to feed 33 lb (15 kg) of tilapia fingerlings, which sustained 189 lettuce plants and produced nearly 3,300 heads of lettuce annually. When integrated systems (fish-hydroponic recirculating units) are compared to separate production systems, the results clearly favor the former. The combined costs and chemical requirements of the separate production systems was nearly two to three times greater than that of the recirculating system to produce the same amount of lettuce and fish. However, there are some drawbacks that must be considered—disease outbreaks in plants and/or fish; the need to critically maintain proper nutrient (especially trace element), plant, and fish levels; uncertainties in fish and market prices; and the need for highly-skilled labor. The integrated method can be adapted to grow other types of vegetables like strawberries, ornamental plants like roses, and other types of animals such as shellfish. Some teachers have even incorporated this technique into their classrooms to illustrate ecological as well as botanical and culture principles.

Some proponents of hydroponic gardening make fairly optimistic claims and state that a sophisticated unit is no more expensive than an equivalent parcel of farmed land. They also argue that hydroponic units (commonly called "hydroponicums") require less attention than terrestrial agriculture. Some examples of different types of "successful" hydroponicums are: a person in the desert area of southern California has used the NFT system for over 18 years and grows his plants void of substate in water contained in open cement troughs that cover 3 acres (7.5 ha); a hydroponicum in Orlando, Florida, utilizes the Japanese system of planting seedlings on styrofoam boards that float on the surface of a nutrient bath which is constantly aerated; an outfit in Queens, New York, uses the Israeli Ein-Gedi system which allows plant roots to hang free inside a tube which is sprayed regularly with a nutrient solution, yielding 150,000 lbs (68,000 kg) of tomatoes, 100,000 lb (45,500 kg) of cucumbers, and one million heads of lettuce per acre (0.4 ha) each year; and finally, a farmer in Blooming Prairie , Minnesota, uses the NFT system in a greenhouse to grow Bibb and leafy lettuce year-round so he can sell his produce to area hospitals, some supermarkets, and a few produce warehouses.

Most people involved in hydroponics agree that the main disadvantage is the high cost for labor, lighting, water, and energy. Root fungal infections can also be easily spread. Advantages include the ability to grow crops in arid regions or where land is at a premium; more controlled conditions, such as the ability to grow plants indoors, and thus minimize pests and weeds; greater planting densities; and constant supply of nutrients. Hydroponic gardening is becoming more popular for home gardeners. It may also be a viable option to growing crops in some developing countries. Overall, the future looks bright for hydroponics.

[John Korstad ]

RESOURCES

BOOKS

Resh, H. M. Hydroponic Food Production: A Definitive Guidebook for the Advanced Home Gardener and Commercial Hydroponci Grower, 5th ed. Santa Barbara: Woodbridge Press, 1995.

Saffell, H. L. How to Start on a Shoestring and Make a Profit with Hydroponics. Franklin, TN: Mayhill Press, 1994.

PERIODICALS

Nicol, E. "Hydroponics and Aquaculture in the High School Classroom." The American Biology Teacher 52 (1990): 182–4.

Rakocy, J. E. "Hydroponic Lettuce Production in a Recirculating Fish Culture System." Island Perspectives 3 (1988–89): 5–10.

Hydroponics

Hydroponics is the process of growing plants in a mixture of mineral nutrients and water; specifically without the use of any type of soil. The two major features of hydroponics are the use of liquid solutions for plant growth and the support of plants with porous materials, such as pebbles or gravel, which let the nutrients into the roots. Plants usually grow by using mineral nutrients from soil and non-mineral nutrients from air and water. With the use of hydroponics, plants do not get the nutrients usually taken from the soil. However, plant physiologists provide each type of plant with the correct amount of each nutrient needed to grow without soil.

There are several early examples of hydroponics, or soil-free agriculture, including the hanging gardens of Babylon and the floating gardens of China and Aztec Mexico. Early Egyptian paintings also depict the growing of plants in water.

In 1600, Belgian physicist Jan Baptista van Helmont (1579–1644) demonstrated that a willow shoot kept in the same soil for five years with routine watering gained 160 lb (13 kg) in weight. As it grew into a full-sized plant, the soil in the container lost only 2 oz (57 g). Clearly, the source of most of the plant’s nutrition was from the water, not the soil.

During the 1860s, German scientist Julius von Sachs (1832–1897) experimented with growing plants in water-nutrient solutions, calling it nutriculture. English philosopher Sir Francis Bacon (1561–1626) published the book Sylva Sylvarum, which is the earliest known book on growing plants without soil. In the eighteenth century, solutions containing mineral nutrients were first developed. In the 1860s, German botanists Wilhelm Knop and Julius von Sachs modified these solutions. Over the following sixty years, laboratory experiments were performed in growing plants without soil.

In 1929, American physician William Frederick Gericke of the University of California first coined the term hydroponics, which means water labor. Gericke demonstrated commercial applications for hydroponics. He became known for his 25-ft (7.6 m) tomato plants. Hydroponics has been shown to double crop yield over that of regular soil. It can be categorized into two subdivisions: water culture, which uses the Sachs water-nutrient solution, with the plants being artificially supported at the base; and gravel culture, which uses an inert medium like sand or gravel to support the plants, to which the water-nutrient solution is added.

Hydroponics was used successfully by American troops stationed on non-arable islands in the Pacific Ocean during the 1940s. In the late 1940s, American horticulturists Robert Withrow and Alice Withrow, of Purdue University (Indiana), designed a practical hydroponic system. Over the twenty years, hydroponic farms developed in the United States and in such countries as France, Germany, Israel, Italy, Spain, Sweden, USSR (what is now Russia), and the United Kingdom. It has also been used to produce foods in such arid countries as Saudi Arabia. In the 1970s, researcher J. Sholto Douglas worked on what he called the Bengal hydroponics system. He sought to simplify the methods and equipment involved in hydroponics so it could be offered as a partial solution for food shortages in India and other developing countries.

Successfully adopted in certain situations, hydroponics will remain in limited use as long as traditional farming methods in natural soil can support the world’s population.

HYDROPONICS

HYDROPONICS, a method of growing plants in nutrient solutions, without soil. Under normal conditions, soil captures and stores nitrogen, potassium, and other mineral nutrients, which plant roots absorb gradually. Hydroponics, in contrast, immerses roots directly in liquid nutrient solutions. Plants are either suspended above water with their roots submerged, or they are placed in sand or in sterile growing mediums and regularly flooded with liquid nutrients. Proponents say this minimizes nutrient loss and allows more precise control over the nutrients the plants receive.

The principles of hydroponic gardening have been used since ancient times. They were brought to popular attention in the United States in 1937 by Dr. W. F. Gericke, who introduced the word "hydroponic" (from the Greek words for "water" and "work") and publicly displayed immense tomato plants cultivated by this method. Hydroponics became a brief fad. Although popular interest subsided, hydroponic methods continued to be developed and studied. In World War II, soldiers on Pacific islands grew their vegetables hydroponically, and in the 1960s large commercial hydroponic greenhouses and multiacre hydroponic farms were established in many locations around the United States.

In the early 2000s hydroponic systems ranged from small home setups to large enterprises. Advocates saw hydroponics as a way to increase the world's food supply and as a form of cultivation suitable for the confines of spacecraft. However, most people viewed hydroponics as a supplement to traditional growing methods rather than as a replacement. It is not suitable for all plants, must be done carefully, and can require large amounts of water.

BIBLIOGRAPHY

Nicholls, Richard. Beginning Hydroponics: Soilless Gardening. Philadelphia: Running Press, 1990.

Resh, Howard M. Hydroponic Food Production: A Definitive Guidebook of Soilless Food-Growing Methods. 5th ed. Santa Barbara, Calif.: Woodbridge Press, 1995.

JohnTownes/c. w.

See alsoAgriculture ; Gardening ; Organic Farming .

Hydroponics

There are several early examples of hydroponics, or soil-free agriculture, including the hanging gardens of Babylon and the floating gardens of China and Aztec Mexico. Early Egyptian paintings also depict the growing of plants in water .

In 1600, the Belgian Jan Baptista van Helmont (1579-1644) demonstrated that a willow shoot kept in the same soil for five years with routine watering gained 160 lb (73 kg) in weight as it grew into a full-sized plant while the soil in the container lost only 2 oz (57g). Clearly, the source of most of the plant's nutrition was from the water, not the soil.

During the 1860s, German scientist Julius von Sachs (1832-1897) experimented with growing plants in water-nutrient solutions, calling it nutriculture.

In 1929, W. F. Gericke of the University of California first coined the term hydroponics, which literally means "water labor." Gericke demonstrated commercial applications for hydroponics and became known for his twenty-five-foot tomato plants. Hydroponics has been shown to double crop yield over that of regular soil. It can be categorized into two subdivisions: water culture, which uses the Sachs water-nutrient solution , with the plants being artificially supported at the base; and gravel culture, which uses an inert medium like sand or gravel to support the plants, to which the water-nutrient solution is added.

Hydroponics was used successfully by American troops stationed on non-arable islands in the Pacific Ocean during the 1940s. It has also been practiced to produce fresh produce in arid countries like Saudi Arabia. In the 1970s, researcher J. Sholto Douglas worked on what he called the Bengal hydroponics system. He sought to simplify the methods and equipment involved in hydroponics so it could be offered as a partial solution for food shortages in India and other developing countries.

Successfully adopted in certain situations, hydroponics will remain in limited use as long as traditional farming methods in natural soil can support the world's population.

Hydroponics

Hydroponics is the practice of growing plants without soil. Plants may be suspended in water or grown in a variety of solid, inert media, including vermiculite (a mineral), sand, and rock wool (fiberglass insulation). In these cases, water that permeates the medium provides the nutrients, while the medium provides support for root structures. Hydroponics allows precise control of nutrient levels and oxygenation of the roots. Many plants grow faster in hydroponic media than in soil, in part because less root growth is needed to find nutrients. However, the precise conditions for each plant differ, and the entire set up must be in a greenhouse, with considerable investment required for lights, tubing, pumps, and other equipment.

While hydroponics is as old as the hanging gardens of Babylon, modern hydroponics was pioneered by Julius von Sachs (1832-1897), a researcher in plant nutrition, and hydroponics is still used for this purpose. It is also used commercially for production of cut flowers, lettuce, tomatoes, and other high-value crops, although it still represents a very small portion of the commercial market.

see also Agriculture, Modern; Roots; Sachs, Julius von.

Richard Robinson

Bibliography

Mason, John. Commerical Hydroponics. New York: Simon & Schuster, 2000.