[EBOOK] HYDROPONIC: Food Production (A Definitive Guidebook for the Advanced Home Gardener and the Commercial Hydroponic Grower, 7th Edition), Howard M. Resh, Copyright By CRC Press

While hydroponics is a fairly recent term used for growing plants without soil, the method dates back much earlier. The hanging gardens of Babylon, the floating gardens of the Aztecs of Mexico, and those of the Chinese were a form of “hydroponic” culture, although not referred to as that. Even Egyptian hieroglyphic records of several hundred years b.c. describe the growing of plants in water. Theophrastus (372–287 b.c.) undertook various experiments in crop nutrition. Botanical studies by Dioscorides date back to the first century A.D.

The earliest recorded scientific approach to discover plant constituents was in 1600 when Belgian Jan van Helmont showed in his classic experiment that plants obtain substances from water. He planted a 5-lb willow shoot in a tube containing 200 lb of dried soil that was covered to keep out dust. After 5 yr of regular watering with rainwater, he found that the willow shoot increased in weight by 160 lb, while the soil lost less than 2 oz. His conclusion that plants obtain substances for growth from water was correct. However, he failed to realize that they also require carbon dioxide and oxygen from the air. In 1699, an Englishman, John Woodward, grew plants in water containing various types of soil and found that the greatest growth occurred in water that contained the most soil. He thereby concluded that plant growth was a result of certain substances in the water, derived from soil, rather than simply from water itself.

Further progress in identifying these substances was slow until more sophisticated research techniques were developed and advances were made in the field of chemistry. In 1804, De Saussure proposed that plants are composed of chemical elements obtained from water, soil, and air. This proposition was verified later in 1851 by Boussingault, a French chemist, in his experiments with plants grown in sand, quartz, and charcoal to which were added solutions of known chemical composition. He concluded that water was essential for plant growth in providing hydrogen and that plant dry matter consisted of hydrogen plus carbon and oxygen, which came from air. He also stated that plants contain nitrogen and other mineral elements.

Researchers had demonstrated by that time that plants could be grown in an inert medium moistened with a water solution containing minerals required by the plants. The next step was to eliminate the medium entirely and grow the plants in a water solution containing these minerals. This was accomplished in 1860–1861 by two German scientists, Sachs and Knop. This was the origin of “nutriculture,” and similar techniques are still used today in laboratory studies of plant physiology and nutrition. These early investigations in plant nutrition demonstrated that normal plant growth can be achieved by immersing the roots of a plant in a water solution containing salts of nitrogen (N), phosphorus (P), sulfur (S), potassium (K), calcium (Ca), and magnesium (Mg), which are now defined as the macroelements or macronutrients (elements required in relatively large amounts).

With further refinements in laboratory techniques and chemistry, scientists discovered seven elements required by plants in relatively small quantities—the microelements or trace elements. These include iron (Fe), chlorine (Cl), manganese (Mn), boron (B), zinc (Zn), copper (Cu), and molybdenum (Mo).

In the following years, researchers developed many diverse basic formulae for the study of plant nutrition. Some of these workers were Arnon, Hoagland, Robbins, Shive, Tollens, Tottingham, and Trelease. Many of their formulae are still used in laboratory research on plant nutrition and physiology.

Interest in practical application of this “nutriculture” did not develop until about 1925 when the greenhouse industry expressed interest in its use. Greenhouse soils had to be replaced frequently to overcome problems of soil structure, fertility, and pests. As a result, research workers became aware of the potential use of nutriculture to replace conventional soil cultural methods. Between 1925 and 1935, extensive development took place in modifying the laboratory techniques of nutriculture to large-scale crop production.

In the early 1930s, W.F. Gericke of the University of California put laboratory experiments in plant nutrition on a commercial scale. In doing so, he termed these nutriculture systems hydroponics. The word was derived from two Greek words hydro (“water”) and ponos (“labor”)—literally “water working.”

Hydroponics can be defined as the science of growing plants without the use of soil, but by the use of an inert medium, such as gravel, sand, peat, vermiculite, pumice, perlite, coco coir, sawdust, rice hulls, or other substrates, to which is added a nutrient solution containing all the essential elements needed by a plant for its normal growth and development. Since many hydroponic methods employ some type of medium it is often termed “soilless culture,” while water culture alone would be true hydroponics.

Using hydroponics, Gericke grew vegetables, including root crops such as beets, radishes, carrots, and potatoes; cereal crops; fruits; ornamentals; and flowers. Using water culture in large tanks, he grew tomatoes to such heights that he had to harvest them with a ladder. The American press made many irrational claims, calling it the discovery of the century. After an unsettled period in which unscrupulous people tried to cash in on the idea by selling useless equipment, more practical research was done and hydroponics became established on a sound scientific basis in horticulture, with recognition of its two principal advantages, high crop yields and its special utility in nonarable regions of the world.

Gericke’s application of hydroponics soon proved itself by providing food for troops stationed on nonarable islands in the Pacific in the early 1940s. In 1945, the U.S. Air Force solved its problem of providing its personnel with fresh vegetables by practicing hydroponics on a large scale on the rocky islands normally incapable of producing such crops.

After World War II, the military command continued to use hydroponics. For example, the U.S. Army established a 22-ha project at Chofu, Japan. The commercial use of hydroponics expanded throughout the world in the 1950s to countries such as Italy, Spain, France, England, Germany, Sweden, the USSR, and Israel.

[EBOOK] HYDROPONIC: Food Production (A Definitive Guidebook for the Advanced Home Gardener and the Commercial Hydroponic Grower, 7th Edition), Howard M. Resh, Copyright By CRC Press

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