Editing Hydroponics (section)

==Techniques==
There are two main variations for each medium: [[irrigation#Subirrigation|sub-irrigation]] and top [[irrigation]]{{specify|Same as Drip irrigation?|date=June 2011}}. Hydroponic techniques aim to simultaneously optimize the water, nutrient and oxygen supply to the plant roots. 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 and fungal growth in the hydroponic medium.{{fact|date=March 2025}}

===Static solution culture===
[[File:CDC South Aquaponics Raft Tank 1 2010-07-17.jpg|thumb|The deep water raft tank at the Crop Diversification Centre (CDC) South [[Aquaponics]] greenhouse in [[Brooks, Alberta]]]]
In static solution culture, plants are grown in containers of nutrient solution, such as glass [[Mason jar]]s (typically, in-home applications), [[Flowerpot|pots]], buckets, tubs, or tanks. The solution is usually gently aerated but may be un-aerated.<ref name=":-3" /> If un-aerated, the solution level is kept low enough that enough roots are above the solution so they get adequate oxygen. A hole is cut (or drilled) in the top of the reservoir for each plant; if it is a jar or tub, it may be its lid, but otherwise, cardboard, foil, paper, wood or metal may be put on top. A single reservoir can be dedicated to a single plant, or to various plants. Reservoir size can be increased as plant size increases. A home-made system can be constructed from food containers or glass canning jars with [[aeration]] provided by an aquarium pump, aquarium airline tubing, aquarium valves or even a [[biofilm]] of [[green algae]] on the glass, through [[photosynthesis]]. Clear containers can also be covered with aluminium foil, butcher paper, black plastic, or other material to eliminate the effects of negative [[phototropism]]. The nutrient solution is changed either on a schedule, such as once per week, or when the concentration drops below a certain level as determined with an [[EC meter|electrical conductivity meter]]. Whenever the solution is depleted below a certain level, either water or fresh nutrient solution is added. A [[Mariotte's bottle]], or a float valve, can 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.<ref name="Suryawanshi Hydroponic Cultivation"/>

===Continuous-flow solution culture===
[[File:Leafy Greens Hydroponics.jpg|thumb|The ''nutrient film technique'' (NFT) being used to grow various salad greens]]
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, pH, and nutrient concentrations can be made in a large storage tank that has potential to serve thousands of plants. A popular variation is the [[nutrient film technique]] or NFT, whereby a very shallow stream of water containing all the dissolved nutrients required for plant growth is recirculated in a thin layer past a bare root mat of plants in a watertight channel, with an upper surface exposed to air. As a consequence, an abundant supply of oxygen is provided 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, provided that 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.<ref>{{cite book |doi=10.1016/B978-0-444-63696-6.00013-X |chapter=Technical Equipment in Soilless Production Systems |title=Soilless Culture |date=2019 |last1=Van Os |first1=E.A. |last2=Gieling |first2=Th. H. |last3=Lieth |first3=J. Heinrich |pages=587–635 |isbn=978-0-444-63696-6 }}</ref>

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. As a consequence, it is recommended that slopes of 1:30 to 1:40 are used.<ref>{{cite web|url=http://www.flairform.com/hints/nft.htm|title=Nutrient Film Technique|website=www.flairform.com|archive-url=https://web.archive.org/web/20180416110457/http://flairform.com/hints/nft.htm|archive-date=2018-04-16|access-date=Nov 22, 2018}}</ref> This allows for minor irregularities in the surface, but, even with these slopes, ponding and [[waterlogging (agriculture)|water logging]] may occur. The slope may be provided by the floor, 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 one liter per minute.{{vague|date=July 2022}}<ref>{{Cite journal|date=Oct 2014|title=What are the fundamentals of setting up an NFT system?|url=http://www.hydroponics.com.au:80/what-are-the-fundamentals-of-setting-up-an-nft-system|journal=Practical Hydroponics & Greenhouses|publisher=Casper Publications|issue=148|archive-url=https://web.archive.org/web/20170904200942/http://www.hydroponics.com.au/what-are-the-fundamentals-of-setting-up-an-nft-system|archive-date=2017-09-04|via=[[Wayback Machine]]|access-date=2017-05-16}}</ref> At planting, rates may be half this and the upper limit of 2 L/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 meters 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. As a consequence, channel length should not exceed 10–15 meters. In situations where this is not possible, the reductions in growth can be eliminated by placing another nutrient feed halfway along the gully and halving the flow rates through each outlet.<ref>{{Cite web |title=Dissolved Oxygen and Water {{!}} U.S. Geological Survey |url=https://www.usgs.gov/special-topics/water-science-school/science/dissolved-oxygen-and-water |access-date=2022-10-19 |website=www.usgs.gov|date=22 October 2019 }}</ref><ref name="Suryawanshi Hydroponic Cultivation"/>

===Aeroponics===
{{Main|Aeroponics}}
[[Aeroponics]] is a system wherein roots are continuously or discontinuously kept 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 [[Atomizer nozzle|atomized nutrients]]. Excellent aeration is the main advantage of aeroponics.
[[File:Systeme AEROPONIC 573px.jpg|thumb|upright=1.5|A diagram of the [[Aeroponics|aeroponic technique]]]]
Aeroponic techniques have proven to be commercially successful for propagation, seed germination, seed potato production, tomato production, leaf crops, and micro-greens.<ref>{{Cite journal|date=2008|title=Commercial Aeroponics: The Grow Anywhere Story|url=https://sivb.org/InVitroReport/42-2/research.htm|journal=In Vitro Report|volume=44|series=Research News|publisher=The Society for In Vitro Biology|issue=2|access-date=2018-11-22|archive-url=https://web.archive.org/web/20170131001154/https://sivb.org/InVitroReport/42-2/research.htm|archive-date=2017-01-31}}</ref> Since inventor Richard Stoner commercialized aeroponic technology in 1983, aeroponics has been implemented as an alternative to water intensive hydroponic systems worldwide.<ref>{{Cite journal|last=Stoner|first=R. J.|date=Sep 22, 1983|title=Aeroponics Versus Bed and Hydroponic Propagation|url=https://www.biocontrols.com/aero28.html|journal=Florists' Review|volume=173|issue=4477|via=AgriHouse}}</ref> A major limitation of hydroponics is the fact that {{convert|1|kg}} of water can only hold {{convert|8|mg}} of air, no matter whether aerators are utilized or not.

Another distinct advantage of aeroponics over hydroponics is that any species of plants can be grown in a true aeroponic system because the microenvironment of an aeroponic can be finely controlled. Another limitation of hydroponics is that certain species of plants can only survive for so long in water before they become [[waterlogging (agriculture)|waterlogged]]. In contrast, suspended aeroponic plants receive 100% of the available oxygen and carbon dioxide to their roots zone, stems, and leaves,<ref>{{Cite journal|last=Stoner|first=R. J.|date=1983|title=Rooting in Air|journal=Greenhouse Grower|volume=1|issue=11}}</ref><ref>{{Cite web |title=Aeroponic System: A Comprehensive Guide for Agriculture Enthusiasts |url=https://www.agriculturelandusa.com/2024/03/Aeroponic-system.html |access-date=2024-05-21 |website=Agriculture land usa |language=en-US}}</ref> thus accelerating biomass growth and reducing rooting times. [[NASA]] research has shown that aeroponically grown plants have an 80% increase in dry weight biomass (essential minerals) compared to hydroponically grown plants. Aeroponics also uses 65% less water than hydroponics. NASA concluded that aeroponically grown plants require ¼ the nutrient input compared to hydroponics.<ref name=":1">{{cite journal |title=Progressive Plant Growing Has Business Blooming |journal=Spinoff 2006 |date=September 2006 |url=https://ntrs.nasa.gov/citations/20070019327 }}</ref><ref>{{cite journal |last1=Ritter |first1=E. |last2=Angulo |first2=B. |last3=Riga |first3=P. |last4=Herrán |first4=C. |last5=Relloso |first5=J. |last6=San Jose |first6=M. |title=Comparison of hydroponic and aeroponic cultivation systems for the production of potato minitubers |journal=Potato Research |date=June 2001 |volume=44 |issue=2 |pages=127–135 |doi=10.1007/bf02410099 }}</ref> Unlike hydroponically grown plants, aeroponically grown plants will not suffer transplant shock when transplanted to soil, and offers growers the ability to reduce the spread of disease and pathogens.{{fact|date=March 2025}}

Aeroponics is also widely used in laboratory studies of plant physiology and plant pathology. Aeroponic techniques have been given special attention from NASA since a mist is easier to handle than a liquid in a zero-gravity environment.<ref name=":1" /><ref name="Suryawanshi Hydroponic Cultivation"/>

===Fogponics===
{{Main|Fogponics}}
Fogponics is a derivation of aeroponics wherein the nutrient solution is aerosolized by a [[ultrasonic humidifier|diaphragm vibrating at ultrasonic frequencies]]. Solution droplets produced by this method tend to be 5–10&nbsp;μm in diameter, smaller than those produced by forcing a nutrient solution through pressurized nozzles, as in aeroponics. The smaller size of the droplets allows them to diffuse through the air more easily, and deliver nutrients to the roots without limiting their access to oxygen.<ref>{{Cite news|url=https://www.maximumyield.com/figuring-out-fogponics/2/1361|title=Figuring Out Fogponics|last=Elliott|first=S.|date=Dec 27, 2016|work=Maximum Yield|access-date=Mar 15, 2017|language=en|archive-date=June 1, 2023|archive-url=https://web.archive.org/web/20230601050951/https://www.maximumyield.com/figuring-out-fogponics/2/1361}}</ref><ref>{{cite journal |last1=Rakib Uddin |first1=M |last2=Suliaman |first2=M F |title=Energy efficient smart indoor fogponics farming system |journal=IOP Conference Series: Earth and Environmental Science |date=February 2021 |volume=673 |issue=1 |pages=012012 |doi=10.1088/1755-1315/673/1/012012 |bibcode=2021E&ES..673a2012R |doi-access=free }}</ref>

===Passive sub-irrigation===
{{Main|Passive hydroponics}}
[[File:Water-cultivate a crocus.jpg|thumb|upright|[[Water plant]]-cultivated [[crocus]]]]
Passive sub-irrigation, also known as passive hydroponics, semi-hydroponics, or ''hydroculture'',<ref>{{Cite news|url=https://www.agriculturelandusa.com/2024/02/Hydroponic-farming.html|title=Hydroponic Farming: How to Grow Plants Without Soil|work=Agriculture land usa|access-date=Feb 13, 2024|language=en-GB}}</ref> is a method wherein plants are grown in an [[Chemically inert|inert]] [[porous]] medium that moves water and fertilizer to the roots by [[capillary action]] from 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 [[ex-clay|expanded clay]] and [[Coir|coconut husk]], contain more air space than more traditional potting mixes, delivering increased oxygen to the roots, which is important in [[epiphyte|epiphytic]] plants such as [[Orchidaceae|orchids]] and [[Bromeliaceae|bromeliads]], whose roots are exposed to the air in nature. Additional advantages of passive hydroponics are the reduction of root rot.{{fact|date=March 2025}}

===Ebb and flow (flood and drain) sub-irrigation===
[[File:Systeme FLOOD&DRAIN 573px.jpg|thumb|An ''ebb and flow'', or ''flood and drain'', hydroponics system]]
{{Main|Ebb and flow hydroponics}}
In its simplest form, nutrient-enriched water is pumped into containers with plants in a growing medium such as [[Expanded clay aggregate]]  At regular intervals, a simple timer causes a pump to fill the containers with nutrient solution, after which the solution drains back down into the reservoir. This keeps the medium regularly flushed with nutrients and air.<ref>{{cite web |url=http://www.makehydroponics.com/whatsystem/flood-and-drain.htm |title=Flood and Drain or Ebb and Flow |publisher=www.makehydroponics.com |access-date=2013-05-17 |archive-url=https://web.archive.org/web/20130217071200/http://www.makehydroponics.com/whatsystem/flood-and-drain.htm |archive-date=2013-02-17  }}</ref>

===Run-to-waste===
In a run-to-waste system, nutrient and water solution is periodically applied to the medium surface. The method was invented in [[Bengal]] in 1946; for this reason it is sometimes referred to as "The Bengal System".{{sfn|Douglas|1975|p=10}}

[[File:Bengal System.png|thumb|A ''run-to-waste'' hydroponics system, referred to as "The [[Bengal]] System" after the region in eastern India where it was invented (circa 1946)]]

This method can be set up in various configurations. In its simplest form, a nutrient-and-water solution is manually applied one or more times per day to a container of inert growing media, such as rockwool, perlite, vermiculite, coco fibre, or sand. In a slightly more complex system, it is automated with a delivery pump, a timer and irrigation tubing to deliver nutrient solution with a delivery frequency that is governed by the key parameters of plant size, plant growing stage, climate, substrate, and substrate conductivity, pH, and water content.{{fact|date=March 2025}}

In a commercial setting, watering frequency is multi-factorial and governed by computers or [[Programmable logic controller|PLCs]].

Commercial hydroponics production of large plants like tomatoes, cucumber, and peppers uses one form or another of run-to-waste hydroponics.

===Deep water culture===
[[File:Hungarian wax peppers roots being revealed IMG 5673.JPG|thumb|upright|The ''deep water culture'' technique being used to grow [[Hungarian wax pepper]]s]]
{{Main|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.
The solution is oxygen saturated by an air pump combined with [[airstone|porous stones]]. With this method, the plants grow much faster because of the high amount of oxygen that the roots receive.<ref name="Growell">{{cite web|url=http://www.growell.co.uk/pr/60/Deep-Water-Culture-It-s-all-about-the-bubbles-.html|title=Deep Water Culture|website=GroWell Hydroponics & Plant Lighting|archive-url=https://web.archive.org/web/20100413041448/http://www.growell.co.uk/pr/60/Deep-Water-Culture-It-s-all-about-the-bubbles-.html|archive-date=April 13, 2010}}</ref> The [[Kratky Method]] is similar to deep water culture, but uses a non-circulating water reservoir.

====Top-fed deep water culture====
''Top-fed'' deep water culture is a technique involving delivering highly oxygenated nutrient solution direct to the root zone of plants. While deep water culture involves the plant roots hanging down into a reservoir of nutrient solution, in top-fed deep water culture the solution is pumped from the reservoir up to the roots (top feeding). The water is released over the plant's roots and then runs back into the reservoir below in a constantly recirculating system. As with deep water culture, there is an [[airstone]] in the reservoir that pumps air into the water via a hose from outside the reservoir. The airstone helps add oxygen to the water. Both the airstone and the water pump run 24 hours a day.{{fact|date=March 2025}}

The biggest advantage of top-fed deep water culture over standard deep water culture is increased growth during the first few weeks.{{citation needed|reason=An important claim likes this needs a good reference.|date=April 2016}} With deep water culture, there is a time when the roots have not reached the water yet. With top-fed deep water culture, the roots get easy access to water from the beginning and will grow to the reservoir below much more quickly than with a deep water culture system. Once the roots have reached the reservoir below, there is not a huge advantage with top-fed deep water culture over standard deep water culture. However, due to the quicker growth in the beginning, grow time can be reduced by a few weeks.{{Citation needed|date=January 2017}}