Aeroponics is the process of growing plants in an air or mist environment without the use of soil or an aggregate medium. Aeroponic culture differs from both hydroponics and in-vitro (Plant tissue culture) growing. Unlike hydroponics, which uses water as a growing medium and essential minerals to sustain plant growth, aeroponics is conducted without a growing medium.
Some growers favor aeroponic systems over other methods of hydroponics because the increased aeration of nutrient solution delivers more oxygen to plant roots, stimulating growth and helping to prevent pathogen formation.
Aeroponics is a form of hydroponic technique. Water is the sole nutrient carrier and typically the method is not hybridized with geoponic technique; although due to the sensitivity of root systems aeroponics is often combined with conventional hydroponics which is used as an emergency 'crop saver' -backup nutrition and water supply- if the aeroponic apparatus fails.
In an aeroponic system the plant's rootzone is suspended into an environment where the roots protrude into an atomized nutrient solution; the leaves and crown, often called the "canopy", extending above. The roots of the plant are separated by the plant support structure. The lowest stem and root system are sprayed or misted for short durations with a hydro-atomized pure water/nutrient solution.
One of the more singular aspects of aeroponic growing is the frequent omission of media, whether organic or not, for anchoring the plant. Many times closed cell foam is compressed around the lower stem and inserted into an opening in the aeroponic chamber, which decreases labor and expense; for larger plants, trellising is used to suspend the weight of vegetation and fruit.
GTi's device incorporated an open-loop water driven apparatus, controlled by a microchip, and delivered a hi-psi, hydro-atomized nutrient spray inside an aeroponic chamber.
At the time, the achievement was revolutionary in terms of a developing (artificial air culture) technology. The Genesis Machine simply connected to a water faucet and an electrical outlet.
Aeroponics has now largely surpassed hydroponics and tissue culture as means for sterile propagation of plant species. With the Genesis Machine, or other comparable aeroponics setup, any grower could clone plants. Due to the automation of most parts of the process, plants could be cloned and grown by the hundreds or even thousands. In short, cloning became easier because the aeroponic apparatus initiated faster and cleaner root development through a sterile, nutrient rich, highly oxygenated, and moist environment (Hughes, 1983).
With the use of aeroponics growers cloned and transplanted air-rooted plants directly into field soil. Aeroponic roots were not susceptible to wilting and leaf loss, or loss due to transplant shock (something hydroponics can never overcome). Because of their healthiness, air-rooted plants were less likely to be infected with pathogens.
The efforts by GTi ushered in a new era of artificial life support for plants capable of growing naturally without the use of soil or hydroponics. GTi received a patent for an all-plastic aeroponic method and apparatus, controlled by a microprocessor in 1985.
Aeroponics became known as a time and cost saver. The economic factors of aeroponic’s contributions to agriculture were taking shape.
Many of these open-loop unit and closed-loop aeroponic systems are still in operation today.
In a true aeroponic apparatus the plant is totally suspended in air, giving the plant access to 100% of the available oxygen in the air. This maximizes the level of oxygen surrounding the stem and root system, accelerating and promoting root growth within the plant. While there is a constant available source of oxygen, the intermittent hydro-atomizing of a spray/mist of the water-nutrient solution provides the necessary moisture and essential minerals to keep plants turgid and alive.
Some researchers have used aeroponics to study the effects of root zone gas composition on plant performance. Soffer and Burger [Soffer et al., 1988] studied the effects of dissolved oxygen concentrations on the formation of adventitious roots in what they termed “aero-hydroponics.” They utilized a 3-tier hydro and aero system, in which three separate zones were formed within the root area. The ends of the roots were submerged in the nutrient reservoir, while the middle of the root section received nutrient mist and the upper portion was above the mist. Their results showed that dissolved O2 is essential to root formation, but went on to show that for the three O2 concentrations tested, the number of roots and root length were always greater in the central misted section than either the submersed section or the un-misted section. Even at the lowest concentration, the misted section rooted successfully.
Growing under lights during the evening allows aeroponics to benefit from the natural occurrence.
A distinct advantage of aeroponic technology is that if a particular plant does become diseased, it can be quickly removed from the plant support structure without disrupting or infecting the other plants.
Due to the disease-free environment that is unique to aeroponics, many plants can grow at higher density (plants per sq meter) when compared to more traditional forms of cultivation (hydroponics, soil and NFT). Commercial aeroponic systems incorporate hardware features that accommodate the crops expanding root systems.
Researcher du Toit, L.J., H.W. Kirby and W.L. Pedersen (1997). “Evaluation of an Aeroponics System to Screen Maize Genotypes for Resistance to Fusarium graminearum Seedling Blight.” These researchers describe aeroponics as a "valuable, simple, and rapid method for preliminary screening of genotypes for resistance to specific seedling blight or root rot.”
The isolating nature of the aeroponic system allowed them to avoid the complications encountered when studying these infections in soil culture.
The key to root development in an aeroponic environment is the size of the water droplet. In commercial applications, a hydro-atomizing spray is employed to cover large areas of roots utilizing air pressure misting.
Water droplet size is crucial for sustaining aeroponic growth. Too large of a water droplet means less oxygen is available to the root system. Too fine of a water droplet, such as those generated by the ultra-sonic mister, produce excessive root hair without developing a lateral root system for sustained growth in an aeroponic system.
Mineralization of the ultra-sonic traducers requires maintenance and potential for component failure. This is also a shortcoming of metal spray jets and misters. Restricted access to the water causes the plant to lose turgidity and wilt.
For long-term growing, the mist system must have significant pressure to force the mist into the dense root system(s). Repeatability is the key to aeroponics and includes the hydro-atomized droplet size. Degradation of the spray due to mineralization of mist heads inhibits the delivery of the water nutrient solution, leading to an environmental imbalance in the air culture environment.
Special low-mass polymer materials were developed and are used to eliminate mineralization in next generation hydro-atomizing misting and spray jets.
In their study, these researchers found that by measuring the concentrations and volumes of input and efflux solutions, they could accurately calculate the nutrient uptake rate (which was verified by comparing the results with N-isotope measurements). After verification of their analytical method, Barak et al. went on to generate additional data specific to the cranberry, such as diurnal variation in nutrient uptake, correlation between ammonium uptake and proton efflux, and the relationship between ion concentration and uptake. Work such as this not only shows the promise of aeroponics as a research tool for nutrient uptake, but also opens up possibilities for the monitoring of plant health and optimization of crops grown in closed environments.
Aeroponic growth refers to growth achieved in an air culture.
Aeroponic system refers to hardware and system components assembled to sustain plants in an air culture.
Aeroponic conditions refers to air culture environmental parameters for sustaining plant growth for a plant species.
Aeroponic roots refers to a root system grown in an air culture.
Hi-pressure aeroponics systems include technologies for air and water purification, nutrient sterilization, low-mass polymers and pressurized nutrient delivery systems.
Biological subsystems and hardware components include effluent controls systems, disease prevention, pathogen resistance features, precision timing and nutrient solution pressurization, heating and cooling sensors, thermal control of solutions, efficient photon-flux light arrays, spectrum filtration spanning, fail-safe sensors and protection, reduced maintenance & labor saving features, and ergonomics and long-term reliability features.
Commercial aeroponic systems, like the hi-pressure devices, are used for the cultivation of high value crops where multiple crop rotations are achieved on an ongoing commercial basis 24/7.
Advanced commercial systems include data gathering, monitoring, analytical feedback and Internet mode connections to various subsystems.
In 1944, L.J. Klotz was the first to discover vapor misted citrus plants in a facilitated research of his studies of diseases of citrus and avocado roots. In 1952, G.F. Trowel grew apple trees in a spray culture.
The ability to precisely control the root zone moisture levels and the amount of water delivered makes aeroponics ideally suited for the study of water stress. K. Hubick [Hubick et al., 1982] evaluated aeroponics as a means to produce consistent, minimally water-stressed plants for use in drought or flood physiology experiments.
Aeroponics is the ideal tool for the study of root morphology. The absence of aggregates offers researchers easy access to the entire, intact root structure without the damage that can be caused by removal of roots from soils or aggregates. It’s been noted that aeroponics produces more normal root systems than hydroponics.
In Israel in 1982, L. Nir, developed a patent for an aeroponic apparatus using comprised low pressure air to deliver a nutrient solution to suspended plants, held by styrofoam, inside large metal containers.
In 1983, R. Stoner filed a patent for the first microprocessor interface to deliver tap water and nutrients into an enclosed aeroponic chamber made of plastic. Stoner has gone on to develop numerous companies researching and advancing aeroponic hardware, interfaces, biocontrols and components for commercial aeroponic crop production.
In 1985, Stoner's company, GTi, was the first company to manufacture, market and apply large scale closed-loop aeroponic systems into greenhouses for commercial crop production.
Stoner is considered the father of commercial aeroponics. Stoner's aeroponic systems are in major developed countries around the world. His aeroponic designs, technology and equipment are widely used at leading agricultural universities worldwide and by commercial growers.
(The Genesis Machine had come a long way fast. Sometime later, the Star Trek TV series sustained the starship’s crew with food grown in its aeroponics-bay.)
Plant experiments were later performed on a variety of Soviet, American, and joint Soviet-American missions, including Biosatellite II, Skylab 3 and 4, Apollo-Soyuz, Sputnik, Vostok, and Zond. Some of the earliest research results showed the effect of low gravity on the orientation of roots and shoots (Halstead and Scott 1990).
Subsequent research went on to investigate the effect of low gravity on plants at the organismic, cellular, and subcellular levels. At the organismic level, for example, a variety of species, including pine, oat, mung bean, lettuce, cress, and Arabidopsis, showed decreased seedling, root, and shoot growth in low gravity, whereas lettuce grown on Cosmos showed the opposite effect of growth in space (Halstead and Scott 1990). Mineral uptake seems also to be affected in plants grown in space. For example, peas grown in space exhibited increased levels of phosphorus and potassium and decreased levels of the divalent cations calcium, magnesium, manganese, zinc, and iron (Halstead and Scott 1990).
By 1997, Stoner’s biocontrol experiments were conducted by NASA. BioServe Space Technologies’s GAP technology (miniature growth chambers) delivered the ODC solution unto bean seeds. Triplicate ODC experiments were conducted in GAP’s flown to the MIR by the space shuttle; at the Kennedy Space Center; and at Colorado State University (J. Linden). All GAPS were housed in total darkness to eliminate light as an experiment variable. The NASA experiment was to study only the benefits of the biocontrol.
NASA's experiments aboard the MIR space station and shuttle confirmed that ODC elicited increased germination rate, better sprouting, increased growth and natural plant disease mechanisms when applied to beans in an enclosed environment. ODC is now a standard for pesticide-free aeroponic growing and organic farming. Soil and hydroponics growers can benefit by incorporating ODC into their planting techniques. ODC meets USDA NOP standards for organic farms.
Abstract: The purpose of the research conducted was to identify and demonstrate technologies for high-performance plant growth in a variety of gravitational environments. A low-gravity environment, for example, poses the problems of effectively bringing water and other nutrients to the plants and effecting recovery of effluents. Food production in the low-gravity environment of space provides further challenges, such as minimization of water use, water handling, and system weight. Food production on planetary bodies such as the Moon or Mars also requires dealing with a hypogravity environment. Because of the impacts to fluid dynamics in these various gravity environments, the nutrient delivery system has been a major focus in plant growth system optimization.
There are a number of methods currently utilized (both in low gravity and on Earth) to deliver nutrients to plants. Substrate dependent methods include traditional soil cultivation, zeoponics, agar, and nutrient-loaded ion exchange resins. In addition to substrate dependent cultivation, many soilless methods have been developed such as nutrient film technique, ebb and flow, aeroponics, and many other variants. Many hydroponic systems can provide high plant performance but nutrient solution throughput is high, necessitating large water volumes and substantial recycling of solutions, and the control of the solution in hypogravity conditions is difficult at best.
Aeroponics, with its use of a hydro-atomized spray to deliver nutrients, minimizes water use, increases oxygenation of roots, and offers excellent plant growth, while at the same time approaching or bettering the low nutrient solution throughput of other systems developed to operate in low gravity. Aeroponics’ elimination of substrates and the need for large nutrient stockpiles reduces the amount of waste materials to be processed by other life support systems. Furthermore, the absence of substrates simplifies planting and harvesting (providing opportunities for automation), decreases the volume and weight of expendable materials, and eliminates a pathway for pathogen transmission. These many advantages combined with the results of this research that prove the viability of aeroponics in microgravity makes aeroponics a logical choice for efficient food production in space.
On Earth, these problems may hinder the economic feasibility of aeroponics for commercial growers. However, such problems become insurmountable obstacles for using these systems on long-duration space missions because of the high cost of payload volume and mass during launch and transit.
The NASA efforts lead to developments of numerous advanced materials for aeroponics for earth and space.
NASA planning scenarios also reveal the Mars surface crew will spend 60% of their time on Mars farming to sustain themselves. Aeroponics is considered the agricultural system of choice because of its low water and power inputs and high volume of food output per sq meter.
Plants grown using aeroponics spend 99.98% of their time in air and 0.02% in direct contact with hydro-atomized nutrient solution. The time spent without water allows the roots to capture oxygen more efficiently. Furthermore, the hydro-atomized mist also significantly contributes to the effective oxygenation of the roots. For example, NFT has a nutrient throughput of 1 L/minute compared to aeroponics’ throughput of 1.5 ml/minute.
The reduced volume of nutrient throughput results in reduced amounts of nutrients required for plant development.
Another benefit of the reduced throughput, of major significance for space-based use, is the reduction in water volume used. This reduction in water volume throughput corresponds with a reduced buffer volume, both of which significantly lighten the weight needed to maintain plant growth. In addition, the volume of effluent from the plants is also reduced with aeroponics, reducing the amount of water that needs to be treated before reuse. The relatively low solution volumes used in aeroponics, coupled with the minimal amount of time that the roots are exposed to the hydro-atomized mist, minimizes root-to-root contact and spread of pathogens between plants.
In 2000, Stoner was granted a patent for an organic disease control biocontrol technology that allows for pesticide-free natural growing in an aeroponic systems.
Stoner received a patent in 2001 for a novel aeroponic method and apparatus utilizing a low pressure mist generated by centrifugal force utilizing a rotating cylinder device. The rotating cylinder device distributes liquid nutrient solution to the roots of plants by use of centrifugal force, thereby eliminating the need for a high pressure and low pressure pump and nozzles, including ultra-sonic misters. The geometrical shape of the enclosed root growth chamber is such that it allows for fractionated droplets to ricochet in multiple random directions thus completely surrounding the plant roots in 360.degree, in any plane.
As recently as 2005, GMO research at South Dakota State University by Dr. Neil Reese applied aeroponics to grow genetically modified corn.
According to Reese it is a historical feat to grow corn in an aeroponic apparatus for bio-massing. The university’s past attempts to grow all types of corn using hydroponics ended in failure.
Using advanced aeroponics techniques to grow genetically modified corn Reese harvested full ears of corn. All the while containing the corn pollen and spent effluent water and preventing them from entering the environment. Containment of these ecologically harmful by-products ensures the environment remains safe from GMO contamination.
Reese says, aeroponics offers the ability to make bio-pharming economically practical.
The historical significants for aeroponics - it's the first time a nation has specifically called out for aeroponics to further an agricultural sector, stimulate farm economic goals, meet increased demands, improve food quality and increase production.
"We have shown that aeroponics, more than any other form of agricultural technology, will significantly improve Vietnam's potato production. We have very little tillable land, aeroponics makes complete economic sense to us”, attested Thach.
Vietnam joined the World Trade Organization (WTO) in January 2007. The impact of aeroponics in Vietnam will be felt at the farm level.
Aeroponic integration in Vietnam agriculture will begin by producing a low cost certified disease-free organic minitubers. Which in turn will be supplied to local farmers for their field plantings of seed potatoes and commercial potatoes. Potato farmers will benefit from aeroponics because their seed potatoes will be disease-free and grown without pesticides. Most importantly for the Vietnamese farmer, it will lower their cost of operation and increase their yields, says Thach.
On the television series Star Trek: Voyager, the starship Voyager is fitted with an aeroponics laboratory by the character Kes for growing herbs and vegetables; the laboratory is occasionally featured as a setting in a number of episodes. On the show, however, the process is referred to as "airponics".
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