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Hydroponic systems are gardening mechanisms designed to bring a regular or continuous flow of water and nutrients to the roots of a plant without the use of soil. Normally, soil is the source for both water and nutrients, but the soil itself is not required by any plant. Hydroponic systems basically work without use of the ‘middleman’.
The term ‘hydroponics’ was coined by the UC Davis professor, Gericke, in 1929. Though hydroponic systems had been experimented with for many years prior, Professor Gericke was the first to demonstrate that plants could be grown to full size without using any soil. He came up with the word hydroponics as a variation of the ancient Greek word for agriculture, ‘geoponics’.
Although there are hundreds of different hydroponic systems used today, they all fall under seven basic categories; passive, water culture, flood and drain, drip, wick, nutrient film technique, and aeroponic.
The ‘passive’ hydoponic system is by far the simplest. The plant is put in a growing medium of some kind, usually perlite, rockwool, gravel or any other substance that has a multitude of air pockets. The medium then sits in a tray of nutrient solution, which is absorbed by the medium by the same simple capillary actions that allow nutrients to flow through soil.
In ‘water culture’ hydroponic systems the plants are suspended above the nutrient medium, and their roots dangle down into it. So long as the nutrient solution is aerated, the roots of any plant will absorb the need nutrients directly without difficulty. Usually there is an air pump and air stone involved to provide the nutrient solution with the needed oxygen.
The ‘flood and drain’ system has growth medium bound plants siting directly in a tray, as in the passive system, which is then flooded at regular intervals with a nutrient solution. There is usually a overflow tube which drains excess solution back into a lower chamber, where the nutrient solution is stored. This hydroponic system is also referred to as the ‘ebb and flow’ system.
Drip and wick hydroponic systems are both similar. In these systems a continuous stream of nutrient solution is delivered to the growth medium in which the plants are in. In the drip system, the solution is dripped over the medium via a pump, and the wick system relies on the capillary draw of a wick to bring in nutrients from a lower reservoir.
The two most advanced hydroponic systems are the ‘nutrient film technique’ (NFT) and ‘aeroponic’ systems. In NFT, the plants roots are suspended into a tray in which a constant stream of nutrient solution is pumped through. The tray is tilted, and the solution runs off back into the reservoir from which it was pumped, never forming more than a thing film along the bottom of the tray. Aeroponics uses a pump that turns the nutrient solution into a fine mist or spray that keeps the roots fed. In both NFT and Aeroponic systems, air is usually the only growth medium.