Hydroponics (from the Greek words "hydro" (water) and "ponos" (labour) is a method of growing
plants using mineral nutrientsolutions, without soil. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as perlite, gravel, or mineral wool. Plant physiologyresearchers discovered in the 19th century that plants absorb essential mineral nutrients as inorganic ionsin water. In natural conditions, soil acts as a mineral nutrient reservoir but the soil itself is not essential to plant growth. When the mineral nutrients in the soil dissolve in water, plant roots are able to absorb them. When the required mineral nutrients are introduced into a plant's water supply artificially, soil is no longer required for the plant to thrive. Almost any terrestrial plant will grow with hydroponics, but some will do better than others. It is also very easy to do; the activity is often undertaken by very young children with such plants as watercress. Hydroponics is also a standard technique in biology research and teaching.
Ancient peoples such as the
Babyloniansand Aztecsused growing techniques where nutrients were obtained from sources other than soil.Fact|date=April 2008 The mineral nutrient solutions used today for hydroponics were not developed until the 1800s.
The earliest published work on growing terrestrial plants without soil was the 1627 book, "Sylva Sylvarum" by Sir
Francis Bacon, printed a year after his death. Water culture became a popular research technique after that. In 1699, John Woodward published his water culture experiments with spearmint. He found that plants in less pure water sources grew better than plants in distilled water. Mineral nutrient solutions for soilless culture of plants were first perfected in the 1860s by the German botanists, Julius von Sachsand Wilhelm Knop. Growth of terrestrial plants without soil in mineral nutrient solutions was called solution culture. It quickly became a standard research and teaching technique and is still widely used today. Solution culture is now considered a type of hydroponics where there is no inert medium.
In 1929, Professor William Frederick Gericke of the University of California at Berkeley began publicly promoting that solution culture be used for agricultural crop production. He first termed it aquaculture but later found that
aquaculturewas already applied to culture of aquatic organisms. Gericke created a sensation by growing tomatoand other plants to a remarkable size in his back yard in mineral nutrient solutions rather than soil. By analogy with the ancient Greekterm for agriculture, geoponics, the science of cultivating the earth, Gericke introduced the term "hydroponics" in 1937 (although he asserts that the term was suggested by Dr. W. A. Setchell, of the University of California) for the culture of plants in water (from the Greek "hydros", "water", and "ponos", "labor").
Reports of Gericke's work and his claims that hydroponics would revolutionize plant agriculture prompted a huge number of requests for further information. Gericke refused to reveal his secrets claiming he had done the work at home on his own time. This refusal eventually resulted in his leaving the University of California. In 1940, he wrote the book, "Complete Guide to Soilless Gardening."
Two other plant nutritionists at the University of California were asked to research Gericke's claims. Dennis R. Hoagland and Daniel I. Arnon wrote a classic 1938 agricultural bulletin, "The Water Culture Method for Growing Plants Without Soil," debunking the exaggerated claims made about hydroponics. Hoagland and Arnon found that hydroponic crop yields were no better than crop yields with good quality soils. Crop yields were ultimately limited by factors other than mineral nutrients, especially light. This research, however, overlooked the fact that hydroponics has other advantages including the fact that the roots of the plant have constant access to oxygen and that the plants have access to as much or as little water as they need. This is important as one of the most common errors when growing is over- and under- watering; and hydroponics prevents this from occurring as large amounts of water can be made available to the plant and any water not used, drained away, recirculated, or actively aerated, eliminating anoxic conditions which drown root systems in soil. In soil, a grower needs to be very experienced to know exactly how much water to feed the plant. Too much and the plant will not be able to access oxygen; too little and the plant will lose the ability to transport nutrients, which are typically moved into the roots while in solution.
These two researchers developed several formulas for mineral nutrient solutions, known as Hoagland solutions. Modified Hoagland solutions are still used today.
One of the early successes of hydroponics occurred on
Wake Island, a rocky atoll in the Pacific Ocean used as a refueling stop for Pan American Airlines. Hydroponics was used there in the 1930s to grow vegetables for the passengers. Hydroponics was a necessity on Wake Island because there was no soil, and it was prohibitively expensive to airlift in fresh vegetables.
In the 1960s, Allen Cooper of England developed the Nutrient Film Technique. The Land Pavilion at Walt Disney World's EPCOT Center opened in 1982 and prominently features a variety of hydroponic techniques. In recent decades,
NASAhas done extensive hydroponic research for their Controlled Ecological Life Support Systemor CELSS. Hydroponics intended to take place on Mars are using LED lighting to grow in different color spectrums with much less heat.
Gericke originally defined hydroponics as crop growth in mineral nutrient solutions, with no solid medium for the roots. He objected in print to people who applied the term hydroponics to other types of soilless culture such as sand culture and gravel culture. The distinction between hydroponics and soilless culture of plants has often been blurred. Soilless culture is a broader term than hydroponics; it only requires that no soils with clay or silt are used. Note that
sandis a type of soil yet sand culture is considered a type of soilless culture. Hydroponics is a subset of soilless culture. Many types of soilless culture do not use the mineral nutrient solutions required for hydroponics.
Billions of container plants are produced annually, including fruit, shade and ornamental trees, shrubs, forest seedlings, vegetable seedlings, bedding plants, herbaceous perennials and vines. Most container plants are produced in soilless media, representing soilless culture. However, most are not hydroponics because the soilless medium often provides some of the mineral nutrients via slow release
fertilizers, cation exchange and decomposition of the organic medium itself. Most soilless media for container plants also contain organic materials such as peator composted bark, which provide some nitrogen to the plant. Greenhouse growth of plants in peat bags is often termed hydroponics, but technically it is not because the medium provides some of the mineral nutrients. Peat has a high cation exchange capacityand must be amended with limestoneto raise the pH value.
The two main types of hydroponics are solution culture and medium culture. Solution culture does not use a solid medium for the roots, just the nutrient solution. The three main types of solution culture are static solution culture, continuous flow solution culture and aeroponics. The medium culture method has a solid medium for the roots and is named for the type of medium, e.g. sand culture, gravel culture or rockwool culture. There are two main variations for each medium, subirrigation and top
irrigation. For all techniques, most hydroponic reservoirs are now built of plastic but other materials have been used including concrete, glass, metal, vegetable solids and wood. The containers should exclude light to prevent algae growth in the nutrient solution.
tatic solution culture
In static solution culture, plants are grown in containers of nutrient solution, such as glass Mason jars (typically in-home applications), plastic buckets, tubs or tanks. The solution is usually gently aerated but may be unaerated. If unaerated, the solution level is kept low enough that enough roots are above the solution so they get adequate oxygen. A hole is cut in the lid of the reservoir for each plant. There can be one to many plants per reservoir. Reservoir size can be increased as plant size increases. A homemade system can be constructed from plastic food containers or glass canning jars with
aerationprovided by an aquarium pump, aquarium airline tubing and aquarium valves. Clear containers are covered with aluminium foil, butcher paper, black plastic or other material to exclude light, thus helping to eliminate the formation of algae. The nutrient solution is either changed on a schedule, such as once per week, or when the concentration drops below a certain level as determined with an electrical conductivity meter. Whenever the solution is depleted below a certain level, either water or fresh nutrient solution is added. A Mariotte's bottlecan be used to automatically maintain the solution level. In raft solution culture, plants are placed in a sheet of buoyant plastic that is floated on the surface of the nutrient solution. That way, the solution level never drops below the roots.
Continuous flow solution culture
In continuous flow solution culture the nutrient solution constantly flows past the roots. It is much easier to automate than the static solution culture because sampling and adjustments to the temperature and nutrient concentrations can be made in a large storage tank that serves potentially thousands of plants. A popular variation is the
nutrient film techniqueor NFT whereby a very shallow stream of water containing all the dissolved nutrients required for plant growth is recirculated past the bare roots of plants in a watertight gully, also known as channels. Ideally, the depth of the recirculating stream should be very shallow, little more than a film of water, hence the name 'nutrient film'. This ensures that the thick root mat, which develops in the bottom of the channel, has an upper surface which, although moist, is in the air. Subsequently, there is an abundant supply of oxygen to the roots of the plants. A properly designed NFT system is based on using the right channel slope, the right flow rate and the right channel length. The main advantage of the NFT system over other forms of hydroponics is that the plant roots are exposed to adequate supplies of water, oxygen and nutrients. In all other forms of production there is a conflict between the supply of these requirements, since excessive or deficient amounts of one results in an imbalance of one or both of the others. NFT, because of its design, provides a system where all three requirements for healthy plant growth can be met at the same time, providing the simple concept of NFT is always remembered and practised. The result of these advantages is that higher yields of high quality produce are obtained over an extended period of cropping. A downside of NFT is that it has very little buffering against interruptions in the flow e.g. power outages, but overall, it is probably one of the more productive techniques.
The same design characteristics apply to all conventional NFT systems. While slopes along channels of 1:100 have been recommended, in practice it is difficult to build a base for channels that is sufficiently true to enable nutrient films to flow without ponding in locally depressed areas. Consequently, it is recommended that slopes of 1:30 to 1:40 are used. This allows for minor irregularities in the surface but, even with these slopes, ponding and waterlogging may occur. The slope may be provided by the floor, or benches or racks may hold the channels and provide the required slope. Both methods are used and depend on local requirements, often determined by the site and crop requirements.
As a general guide, flow rates for each gully should be 1 liter per minute. At planting, rates may be half this and the upper limit of 2L/min appears about the maximum. Flow rates beyond these extremes are often associated with nutritional problems. Depressed growth rates of many crops have been observed when channels exceed 12 metres in length. On rapidly growing crops, tests have indicated that, while oxygen levels remain adequate, nitrogen may be depleted over the length of the gully. Consequently, channel length should not exceed 10-15 metres. In situations where this is not possible, the reductions in growth can be eliminated by placing another nutrient feed half way along the gully and reducing flow rates to 1L/min through each outlet.
Aeroponics is a system where roots are continuously or discontinuously in an environment saturated with fine drops (a mist or aerosol) of nutrient solution. The method requires no substrate and entails growing plants with their roots suspended in a deep air or growth chamber with the roots periodically wetted with a fine mist of atomized nutrients. Excellent aeration is the main advantage of aeroponics.
Aeroponic techniques have proved very successful for propagation, but have yet to prove themselves on a commercial scale. Aeroponics is also widely used in laboratory studies of plant physiology. Aeroponic techniques have been given special attention from
NASAsince a mist is easier to handle than a liquid in a zero gravity environment.
Passive subirrigation, also known as passive hydroponics or semi-hydroponics, is a method where plants are grown in an
inert porousmedium that transports water and fertilizer to the roots by capillary actionfrom a separate reservoir as necessary, reducing labor and providing a constant supply of water to the roots. In the simplest method, the pot sits in a shallow solution of fertilizer and water or on a capillary mat saturated with nutrient solution. The various hydroponic media available, such as expanded clay and coconut husk, contain more air space than more traditional potting mixes, delivering increased oxygen to the roots, which is important in epiphytic plants such as orchids and bromeliads, whose roots are exposed to the air in nature. Additional advantages of passive hydroponics are the reduction of root rot and the additional ambient humidity provided through evaporation.
Ebb and flow / Flood and drain subirrigation
In its simplest form, there is a tray above a reservoir of nutrient solution. The tray is either filled with growing medium (clay granules being the most common) and planted directly, or pots of medium stand in the tray. At regular intervals, a simple timer causes a pump to fill the upper tray with nutrient solution, after which the solution drains back down into the reservoir. This keeps the medium regularly flushed with nutrients and air.
In top irrigation, nutrient solution is periodically applied to the medium surface. This may be done manually once per day in large containers of some media, such as sand. Usually, it is automated with a pump, timer and drip irrigation tubing to deliver nutrient solution as frequently as 5 to 10 minutes every hour.
Deep water culture
The hydroponic method of plant production by means of suspending the plant roots in a solution of nutrient rich, oxygenated water. Traditional methods favor the use of plastic buckets and large containers with the plant contained in a net pot suspended from the centre of the lid and the roots suspended in the nutrient solution.
One of the most obvious decisions hydroponicists have to make is which medium they should use. Different media are appropriate for different growing techniques.
Diahydro is a natural sedimentary rock medium that consists of the fossilized remains of
diatoms. Diahydro is extremely high in Silica (87-94%), an essential component for the growth of plants and strengthening of cell walls.
Baked clay pellets, also known under the
trademarks 'Hydroton' or LECA(light expanded clayaggregate), are suitable for hydroponic systems in which all nutrients are carefully controlled in water solution. The clay pellets are inert, pHneutral and do not contain any nutrient value.
The clay is formed into round pellets and fired in rotary
kilns at 1200°C. This causes the clay to expand, like popcorn, and become porous. It is light in weight, and does not compact over time. Shape of individual pellet can be irregular or uniform depending on brand and manufacturing process. The manufacturers consider expanded clay to be an ecologically sustainable and re-usable growing medium because of its ability to be cleaned and sterilized, typically by washing in solutions of white vinegar, chlorine bleachor hydrogen peroxide(H2O2), and rinsing completely.
A less popular view is that clay pebbles are best not re-used even when they are cleaned, due to root growth which may enter the medium. Breaking open a clay pebble after a crop has been grown will reveal this growth.
Rock wool(mineral wool) is probably the most widely used medium in hydroponics. Rockwool is an inert substrate for both 'free drainage' and recirculating systems.
Coco peat, also known as
coiror coco, is the leftover material after the fibres have been removed from the outermost shell (bolster) of the coconut. Coir is a 100% natural grow and flowering medium.
Perliteis a volcanic rock that has been superheated into very lightweight expanded glass pebbles. It is used loose or in plastic sleeves immersed in the water. It is also used in potting soil mixes to decrease soil density. Perlite has similar properties and uses to vermiculitebut generally holds more air and less water. If not contained, it can float if flood and drain feeding is used.
vermiculiteis another mineral that has been superheated until it has expanded into light pebbles. Vermiculite holds more water than perlite and has a natural "wicking" property that can draw water and nutrients in a passive hydroponic system. If too much water and not enough air surrounds the plants roots, it's possible to gradually lower the medium's water-retention capability by mixing in increasing quantities of perlite.
Sand is cheap and easily available. However, it is heavy, it does not always drain well, and it must be sterilized between use.
The same type that is used in aquariums, though any small gravel can be used, provided it is washed first. Indeed, plants growing in a typical traditional gravel filter bed, with water circulated using electric powerhead pumps, are in effect being grown using gravel hydroponics. Gravel is inexpensive, easy to keep clean, drains well and won't become waterlogged. However, it is also heavy, and if the system doesn't provide continuous water, the plant roots may dry out.
Brick shards have similar properties to gravel. They have the added disadvantages of possibly altering the pH and requiring extra cleaning before reuse.
Polystyrene packing peanuts
packing peanutsare inexpensive, readily available, and have excellent drainage. However, they can be too lightweight for some uses. They are mainly used in closed tube systems. Note that polystyrenepeanuts must be used; biodegradable packing peanuts will decompose into a sludge. Plants may absorb styreneand pass it to their consumers; this is a possible health risk.
nutrients are dissolved in the water used in hydroponics and are mostly in inorganic and ionic form. Primary among the dissolved cations (positively-charged ions) are Ca2+ ( calcium), Mg2+ ( magnesium), and K+ ( potassium); the major nutrient anions in nutrient solutions are NO3− ( nitrate), SO42− ( sulfate), and H2PO4− ( dihydrogen phosphate).
Numerous 'recipes' for hydroponic solutions are available. Many use different combinations of chemicals to reach similar total final compositions. Commonly-used chemicals for the macronutrients include
potassium nitrate, calcium nitrate, potassium phosphate, and magnesium sulfate. Various micronutrients are typically added to hydroponic solutions to supply essential elements; among them are Fe ( iron), Mn ( manganese), Cu ( copper), Zn ( zinc), B ( boron), Cl ( chlorine), and Ni ( nickel). Chelatingagents are sometimes used to keep Fe soluble. Many variations of the nutrient solutions used by Arnon and Hoagland (see above) have been styled 'modified Hoagland solutions' and are widely used.
Plants will change the composition of the nutrient solutions upon contact by depleting specific nutrients more rapidly than others, removing water from the solution, and altering the
pHby excretion of either acidity or alkalinity. Care is required not to allow salt concentrations to become too high, nutrients to become too depleted, or pH to wander far from the desired value.
Due to its arid climate,
Israelhas developed advanced hydroponic technology. They have marketed their system to Nicaragua, which uses it to produce more than one million pounds of peppers annually for sale abroad, including the United States.
The largest commercial hydroponics facility in the world is Eurofresh Farms in
Willcox, Arizona, which sold 125 million pounds of tomatoes in 2005. [Kenney, Brad P. 2006. Success under glass. "American Vegetable Grower." May, pages 12-13. [http://www.eurofresh.com/pressroom/success.swf] ] Eurofresh has 256 acres under glass and represents about a third of the commercial hydroponic greenhouse area in the U.S. Sorenson, Dan. 2006. Hydroponic tomatoes. "Arizona Daily Star" [http://cals.arizona.edu/media/archives/5.33.html] ] Eurofresh does not consider their tomatoes organic, but they are pesticide-free. They are grown in rockwool with top irrigation.
Some commercial installations use no
pesticides or herbicides, preferring integrated pest managementtechniques. There is often a price premium willingly paid by consumers for produce which is labeled "organic". Some states in the USA require soil as an essential to obtain organic certification. There are also overlapping and somewhat contradictory rules established by the US Federal Government, so some food grown with hydroponics can be certified organic.
Hydroponics also saves an incredible amount of water; it uses as little as 1/20 the amount as a regular farm to produce the same amount of food. The
water tablecan be impacted by the water use and run-offof chemicals from farms, but hydroponics may minimize impact as well as having the advantage that water use and water returns are easier to measure. This can save the farmer money by allowing reduced water use and the ability to measure consequences to the land around a farm.
To increase plant growth, lighting systems such as
metal halideor high pressure sodiumare used to lengthen the day or to supplement natural sunshine if it is scarce. Metal halide emits more light in the blue spectrum, making it ideal for plant growth. High pressure sodium emits more light in the red spectrum, meaning that it is best suited for supplementing natural sunshine. However, these lighting systems require large amounts of electricity (and hence high electrical expenses) to operate.
The environment in a hydroponics
greenhouseis tightly controlled for maximum efficiency and this new mindset is called Soil-less/Controlled Environment Agriculture (S/CEA). With this growers can make ultra-premium foods anywhere in the world, regardless of temperature and growing seasons. Growers monitor the temperature, humidity, and pHlevel constantly.
Hydroponics have been used to enhance vegetables to provide more nutritional value. A hydroponic farmer in
Virginiahas developed a calciumand potassiumenriched head of lettuce, scheduled to be widely available in April 2007. Grocers in test markets have said that the lettuce sells "very well", and the farmers claim that their hydroponic lettuce uses 90% less water than traditional soil farming. [Murphy, Katie. 2006. Farm Grows Hydroponic Lettuce. "Observer Online" [http://www.observernews.com/stories/current/news/120106/Lettuce.shtml] ]
With pest problems reduced, and nutrients constantly fed to the roots, productivity in hydroponics is high, plant growth being limited by the low levels of
carbon dioxidein the atmosphere, or limited light. To increase yield further, some sealed greenhouses inject carbon dioxide into their environment to help growth (CO2 enrichment), or add lights to lengthen the day, control vegetative growth etc.fact|date=May 2008
* [http://www.soils.wisc.edu/courses/soils326/hydropon.htm Barak, P. 2002. Essential Elements for Plant Growth: Hydroponics.]
*Hershey, D.R. 1994. Solution culture hydroponics: history and inexpensive equipment. "American Biology Teacher" 56:111-118.
* [http://ag.arizona.edu/PLS/faculty/MERLE.html Jensen, M.H. 1997. Hydroponics. "HortScience" 32]
* [http://www.aces.uiuc.edu/vista/html_pubs/hydro/hydrotoc.html "Hydroponics as a Hobby: Growing Plants Without Soil." University of Illinois Circular 844]
* [http://www.usu.edu/cpl/research_hydroponics.htm Utah State University Hydroponics]
* [http://www.schundler.com/mcmurdo.htm Hydroponics at McMurdo Station Antarctica]
* [http://www.cornellcea.com/handbook_home.htm Cornell University Commercial Hydroponic Lettuce, Spinach and Pak Choi Grower's Handbooks]
* [http://www.epa.gov/Ozone/mbr/casestudies/volume3/hydropn3.html Hydroponics and Soilless Cultures on Artificial Substrates as an Alternative to Methyl Bromide Soil Fumigation]
* [http://www.popsci.com/cliff-kuang/article/2008-09/farming-sky Robotically tended hydroponic crops] , (
External links with commercial advertising
* [http://www.hydroponicsonline.com/lessons/table-of-contents.htm Hydroponic Lesson Plans]
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Look at other dictionaries:
hydroponics — 1937, formed in English from HYDRO (Cf. hydro ) + ponics, from Gk. ponein to labor, toil, from ponos labor (see SPAN (Cf. span) (v.)). Related: Hydroponic (adj.) … Etymology dictionary
hydroponics — ► PLURAL NOUN (treated as sing. ) ▪ the growing of plants in sand, gravel, or liquid, with added nutrients but without soil. DERIVATIVES hydroponic adjective hydroponically adverb. ORIGIN from Greek hud r water + ponos labour … English terms dictionary
hydroponics — ☆ hydroponics [hī΄drə pän′iks ] n. [ HYDRO + (GEO)PON(IC) + ICS] the science of growing or the production of plants in nutrient rich solutions or moist inert material, instead of in soil hydroponic adj. hydroponically adv. hydroponicist [hī΄drə… … English World dictionary
hydroponics — hydroponic, adj. hydroponically, adv. hydroponist /huy drop euh nist/, hydroponicist, n. /huy dreuh pon iks/, n. (used with a sing. v.) the cultivation of plants by placing the roots in liquid nutrient solutions rather than in soil; soilless… … Universalium
hydroponics — hidroponika statusas T sritis ekologija ir aplinkotyra apibrėžtis Augalų auginimas maistinguose tirpaluose be dirvožemio. atitikmenys: angl. hydroponics vok. Hydroponik, f rus. водная культура, f; гидропоника, f … Ekologijos terminų aiškinamasis žodynas
hydroponics — hidroponika statusas T sritis augalininkystė apibrėžtis Augalų auginimas maitinamuosiuose tirpaluose be dirvožemio. atitikmenys: angl. hydroponics rus. гидропоника … Žemės ūkio augalų selekcijos ir sėklininkystės terminų žodynas
hydroponics — noun plural but singular in construction Etymology: hydr + ponics (as in geoponics agriculture) Date: 1937 the growing of plants in nutrient solutions with or without an inert medium (as soil) to provide mechanical support • hydroponic adjective… … New Collegiate Dictionary
hydroponics — noun the cultivation of plants in a nutrient solution rather than in the soil … Wiktionary
hydroponics — Synonyms and related words: agrarianism, agricultural geology, agriculture, agrology, agronomics, agronomy, algology, aquiculture, botany, bryology, contour farming, cultivation, culture, dendrology, dirt farming, dry farming, dryland farming,… … Moby Thesaurus
hydroponics — hy|dro|pon|ics [ ,haıdrə panıks ] noun uncount a method of growing plants in water that has special food in it but no soil … Usage of the words and phrases in modern English