For saving space and soil, this method also has several
other benefits, including no soil-borne diseases, no
weeds to pull and no soil to till, run-of-the-mill side
benefits of soil-less gardening.

Hydroponics development History

The development of hydroponics has not been rapid. Although the first use of CEA was the growing of off-season cucumbers under "transparent stone" (mica) for the Roman Emperor Tiberius during the 1st century, the technology is believed to have been used little, if at all, for the following 1500 years.

Greenhouses (experimental hydroponics) appeared in France and England during the 17th century; Woodward grew mint plants without soil in England in the year 1699. The basic laboratory techniques of nutrient solution culture were developed (independently) by Sachs and Knap in Germany about 1860 (Hoagland and Arnon, 1938).

In the United States, interest began to develop in the possible use of complete nutrient solutions for large-scale crop production about 1925. Greenhouse soils had to be replaced at frequent intervals or else be maintained in good condition from year to year by adding large quantities of commercial fertilizers. As a result of these difficulties, research workers in certain U.S. agricultural experiment stations turned to nutrient solution culture methods as a means of replacing the natural soil system with either an aerated nutrient solution or an artificial soil composed of chemically inert aggregates moistened with nutrient solutions (Withrow and Withrow, 1948).

Between 1925 and 1935, extensive development took place in modifying the methods of the plant physiologists to large-scale crop production. Workers at the New Jersey Agricultural Experiment Station improved the sand culture method (Shive and Robbins, 1937). The water and sand culture methods were used for large-scale production by investigators at the California Agricultural Experiment Station (Hoagland and Arnon, 1938). Each of these two methods involved certain fundamental limitations for commercial crop production, which partially were overcome with the introduction of the subirrigation system initiated in 1934 at the New Jersey and Indiana Agricultural Experiment Stations (Withrow and Withrow, 1948). Gericke (1940) published a description of a quasi-commercial use of the liquid technique and apparently coined the word hydroponics in passing. The technology was used in a few limited applications on Pacific islands during World War II. After the war, Purdue Univ. popularized hydroponics (called nutriculture) in a classic series of extension service bulletins (Withrow and Withrow, 1948) describing the precise delivery of nutrient solution to plant roots in either liquid or aggregate systems. While there was commercial interest in the use of such systems, hydroponics or nutriculture was not widely accepted because of the high cost in construction of the concrete growing beds.

After a period of ~20 years, interest in hydroponics was renewed with the advent of plastics. Plastics were used not only in the glazing of greenhouses, but also in place of concrete in lining the growing beds. Plastics were also important in the introduction of drip irrigation. Numerous promotional schemes involving hydroponics became common with huge investments made in growing systems.

Greenhouse areas began to expand significantly in Europe and Asia during the 1950s and 1960s, and large hydroponic systems were developed in the deserts of California, Arizona, Abu Dhabi, and Iran about 1970 (Fontes, 1973; Jensen and Teran, 1971). In these desert locations, the advantages of the technology were augmented by the duration and interest of the solar radiation, which maximized photosynthetic production.

Unfortunately, escalating oil prices, starting in 1973, substantially increased the costs of CEA heating and cooling by one or two orders of magnitude. This, along with fewer chemicals registered for pest control, caused many bankruptcies and a decreasing interest in hydroponics, especially in the United States.

Since the inception of hydroponics, research to refine the methodology has continued. In the late 1960s researchers at the Glasshouse Crops Research Institute (GCRI), Littlehampton, England developed the nutrient film technique along with a number of subsequent refinements (Graves, 1983). This research gave rise to the hydroponic systems used today. Jensen and Collins (1985) published a complete review of hydroponics highlighting many new cultural systems developed in Europe and the United States.

Almost 20 years have passed since the last real commercial interest in hydroponics, but today there is renewed interest among growers establishing CEA/hydroponic systems. This is especially true in regions where there is concern about controlling pollution of ground water with nutrient wastes or soil sterilants. Today growers appear to be much more critical in regard to site selection, structures, the growing system, pest control, and markets.

Controlled Environment Agriculture
Prior to 1970, the greenhouse vegetable industry was located near the high-population centers, mainly in the states of Ohio, Michigan, and Massachusetts. In 1867, a committee of the Massachusetts Horticultural Society noted the rapid growth of vegetables under glass and suggested that prizes be offered to encourage the practice (Massachusetts Horticultural Society, 1880). All commercial production was in soil.

In 1965, Ohio was the major greenhouse vegetable region in the United States, with more than 240 ha. After 1970, with the rapid rise in energy cost to heat greenhouses, along with the construction of superhighways to transport fresh produce from southern regions, Ohio became an importer of tomatoes. Today, the greenhouse vegetable industry in these eastern states has collapsed and is insignificant.

With the superhighways in America, the energy required to transport fresh vegetables from the southern region of the United States and from Mexico is less than that required to heat a greenhouse. For example, in conventional greenhouses in Ohio, nearly 40,000 kcal of energy are required to grow 1 kg of tomatoes vs. only 4000 kcal in the open field. Shipping 1 kg of tomatoes 5000 km north by semi-truck expends only 1865 kcal of energy.

Along with the light factor are temperature considerations, especially in the southwest desert. For example, if tomatoes are selected as the crop to be grown year-round, low elevations must be avoided, due to the difficulty in maintaining desirable temperatures in the greenhouse during late spring and early fall, even with fan and pad cooling. In the late 1960s, hydroponic installations were installed in low-elevation regions in Texas and Arizona. In most regions of Texas, evaporative cooling is ineffective due to high ambient humidity. Escalating energy costs in the 1970s added to the costs of cooling in the summer, as well as heating during the winter months. This, coupled with insect and disease problems and high amortization costs, especially when growers were purchasing turnkey greenhouse systems rather than building their own growing system, caused most hydroponic installations to fail financially. This was true not only in Texas and Arizona, but throughout the United States.

Given the high cost of fan and pad equipment, future hydroponic growers will be selecting sites at specific elevations that have summer temperatures that do not require evaporative cooling, therefore sparing the costs of such cooling equipment. At the same time, an elevation should be selected that is not too high in order to avoid high heating costs in winter. In southern Arizona, such an elevation for tomato production would range from 1250 to 1675 m and for cucumber production, 600 to 1250 m.

Proposed as an alternative to fan and pad cooling is high-pressure fog systems. Recent experiences have proven this method of cooling desirable if the feed water is absolutely free of any undissolved or dissolved solids. It is important for the greenhouse structure to have ridge vents to accommodate ample air exchange for prescribed temperature and humidity control. Any time a grower deviates from the prescribed growing temperatures for a given crop, yields will be lowered. The more a grower has to cool or heat a greenhouse in order to maintain recommended temperatures, the greater the cost to operate the facility, therefore lessening financial return. If evaporative cooling systems are used, locating the greenhouse in a region of low outdoor humidity is important.

Especially important is selection of a site free of insects that might be vectors for severe virus diseases. Early hydroponic ventures did not consider this. In the United States and Mexico, sites were selected where white flies existed. These can be a vector of gemini viruses, which are extremely lethal to most solanaceous and cucurbit crops. Screens on air intakes do not always work, as the white fly almost always gains entry into the growing area. Growing in regions where there are mild winters normally increases the incidence of insects and diseases due to the continued life cycle of the pest. Selecting a site that isn't already a major producer of vegetable crops is also advisable.

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