Agriculture Reference
In-Depth Information
6
Water Culture (True
Hydroponic Systems)
HYDROPONICS VS. SOILLESS CULTURE
By definition
hydroponics
means “hydro” (water) and “ponos” (working),
literally “water working.” In a broad sense hydroponics means growing
plants without the use of soil, but with or without some inert substrate.
Hence, it can also be termed “soilless culture.” True hydroponic culture
then would be a water culture system without the use of a medium. Today
the most common methods of true hydroponic culture are nutrient film
technique (NFT) and water culture such as the raft culture system. When a
nutrient solution is applied to plant roots from below as a mist this culture
is termed “aeroponics.” It is also a true hydroponic system.
The most common form of hydroponic culture today is really soilless
culture. However, since the same principles of nutrition apply as with
true hydroponics most people never differentiate between soilless culture
and hydroponics. Many plants, especially longer cropping ones such as
tomatoes, eggplants, peppers, and cucumbers, prefer some form of soil-
less culture over water culture. There are a number of important factors in
choosing the best medium for specific plants. The medium must be ster-
ile, that is, free of pests and diseases, have good water retention but not
excessive, good oxygenation for plant roots, and retain its structural integ-
rity so as not to compact resulting in insufficient oxygen for the roots of
plants. Rockwool and coco coir are the two most popular substrates today.
However, depending upon what is available in your area other suitable sub-
strates include peat, rice hulls, perlite, sawdust, bark chips, vermiculite,
sand, gravel, haydite (porous shale), leca (light expanded clay aggregate)
(clay pellets), and volcanic rock (pumice). Often mixtures of peat, peatlite,
sand, coco coir, and rice hulls make a good medium.
WATER CULTURE SYSTEMS
At present NFT is the most popular water culture system. However, large
commercial operations growing lettuce are using the raft culture system.
The principle of NFT is to have a shallow flow of water under the roots.
The flow must be constant and thin to oxygenate the roots of the plants.
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