Principles of Operation
The fundamental principle of hydroponics relies on fertilized and aerated water which provides both nutrition and oxygen to a plant's root zone. It often involves relatively sophisticated mechanization processes which can be daunting to casual hobbyists. Nutrient solutions must usually be below the temperature at which pathogen growth can begin, yet not so cool that root activity is suppressed. Active aeration of the fertilizer solution is common, since root systems themselves remove oxygen, creating conditions which also can promote pathogenic bacteria and water-borne molds.
E&F utilizes the fact that the solution is not left in constant contact with the roots of plants, to avoid the need for oxygenating or chilling of the solution. Instead it relies on characteristics of root function to provide passive oxygenation at a high level which tends to suppress pathogen growth.
Simplicity is maintained through usage of a single, two-directional path for the solution. Water flows in and out using the same tube. When the pump has raised water into the tray, briefly submerging the roots, the pump is rendered inactive using a switch, typically a timer, and the water flows back down the same tube. This eliminates the need for more than one sealed fitting and reduces overall complexity of the system.
Ebb and flow systems come on according to the water-holding capacity of the medium in which the roots sit. Highly water-retentive media can require watering only once a day, while others require two to as many as six floodings, with each "flood" stage only lasting a few minutes. The time it takes to flood the roots is not a critical parameter, which means that pumps are often moderate in capacity and can be small for systems sustaining indoor plants. This makes the method popular with amateur and urban gardeners. Gravity acts as drain pump, and aeration is accomplished through thin-filming and positive displacement of air as it is forced out of the root zone by water.
Read more about this topic: Ebb And Flow
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