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Gardening

Aeroponics

NASA-Aeroponics_International-lettuce-day12Aeroponics is the process of growing plants in an air or mist environment without the use of soil or an aggregate medium (known as geoponics).

The word “aeroponic” is derived from the Greek meanings of “aero” (air) and “ponos” (labour). Aeroponic culture differs from both conventional 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. Because water is used in aeroponics to transmit nutrients, it is sometimes considered a type of hydroponics.

Methods

The basic principle of aeroponic growing is to grow plants suspended in a closed or semi-closed environment by spraying the plant’s dangling roots and lower stem with an atomized, nutrient-rich water solution. The leaves and crown, often called the “canopy”, extend above. The roots of the plant are separated by the plant support structure. 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.

Ideally, the environment is kept free from pests and disease so that the plants may grow healthier and quicker than plants grown in a medium.

However, since most aeroponic environments are not perfectly closed off to the outside, pests and disease may still cause a threat. Controlled environments advance plant development, health, growth, flowering and fruiting for any given plant species.

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.

Ecological advantages

Aeroponic growing is considered to be safe and ecologically friendly for producing natural, healthy plants and crops.

The main ecological advantages of aeroponics are the conservation of water and energy. When compared to hydroponics, aeroponics offers lower water and energy inputs per square meter of growing area.

When used commercially, Aeroponics uses one-tenth of the water otherwise necessary to grow the crop but this can be reduced to as little as one-twentieth.

NASA has funded research and development of new advanced materials to improve aeroponic reliability and maintenance reduction. It also has determined that high pressure hydro-atomized mist of 5-50 micrometres micro-droplets is necessary for long-term aeroponic growing.

For long-term growing, the mist system must have significant pressure to force the mist into the dense root system. 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.

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.

More control of plant environment

Aeroponics allows more control of the environment around the root zone, as, unlike other plant growth systems, the plant roots are not constantly surrounded by some medium (as, for example, with hydroponics, where the roots are constantly immersed in water).

A variety of different nutrient solutions can be administered to the root zone using aeroponics without needing to flush out any solution or matrix in which the roots had previously been immersed. This elevated level of control would be useful when researching the effect of a varied regimen of nutrient application to the roots of a plant species of interest. In a similar manner, aeroponics allows a greater range of growth conditions than other nutrient delivery systems. The interval and duration of the nutrient spray, for example, can be very finely attuned to the needs of a specific plant species. The aerial tissue can be subjected to a completely different environment from that of the roots.

More user-friendly

The design of an aeroponic system allows ease of working with the plants. This results from the separation of the plants from each other, and the fact that the plants are suspended in air and the roots are not entrapped in any kind of matrix. Consequently, the harvesting of individual plants is quite simple and straightforward. Likewise, removal of any plant that may be infected with some type of pathogen is easily accomplished without risk of uprooting or contaminating nearby plants.

More cost effective

Aeroponic systems are more cost effective than other systems. Because of the reduced volume of solution throughput (discussed above), less water and less nutrients are needed in the system at any given time compared to other nutrient delivery systems. The need for substrates is also eliminated, as is the need for many moving parts, resulting in lowered manufacturing cost and reduced maintenance costs.

Pathogen control and disease prevention

Plants are most susceptible to loss from pathogens during the first 21 days of their life cycle.

The aeroponic technology developed by the PI utilizes a patented plant support structure that separates the plants from one another. In a hydroponic or aggregate-based system, pathogen infections can easily spread throughout the entire system due to the plants’ common source of water or medium. In the ideal aeroponic system pathogens can be reduced and controlled by:

* separating the plants – thus preventing the pathogen from spreading infection from one plant to another.

* applying disinfectants and fungicides to the aerial and root zones individually,

* applying the water/nutrient at intervals that are best suited for plant development and growth,

* allowing the plant to expand without interference of restricting physical barriers,

* reducing the per plant exposure to surfaces where pathogens can linger or proliferate.

Use of seed stocks

With aeroponics, the deleterious effects of seed stocks that are infected with pathogens can be minimized. As discussed above, this is due to the separation of the plants and the lack of shared growth matrix. In addition, due to the enclosed, controlled environment, aeroponics can be an ideal growth system in which to grow seed stocks that are pathogen-free. The enclosing of the growth chamber, in addition to the isolation of the plants from each other discussed above, helps to both prevent initial contamination from pathogens introduced from the external environment and minimize the spread from one plant to others of any pathogens that may exist.

For more indoor,outdoor, and hydroponics information, please visit San Diego Hydroponics & Organics website.

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