Hydroponic Systems for Plant Growth
Recirculating hydroponic systems for growing plants can be divided into 5 fundamental categories, the primary difference being in how the nutrient solution is delivered to the plant roots:
Nutrient Film Technique | NFT
Nutrient Film Technique, or NFT, is a hydroponic method that produces multiple plants without any growing media in a tube or channel, similar to a rain gutter, mounted on a very slight incline. The nutrient solution is pumped from a separate reservoir to the high side of the channels, which then flows continuously via gravity in a very shallow “film”, perhaps an 1/8 of an inch deep, through the channel, bathing the roots of the plants as it travels towards the low end of the incline, where it is collected and recycled back into the nutrient reservoir.
The roots tend to intertwine and spread along the bottoms of the channels where the lower roots are constantly bathed in nutrient solution, however, since much of the root mass is not submerged, high oxygen levels are available at all times to the root systems.
Ebb & Flow | Ebb & Flood | Flood & Drain | Subirrigation
Known variously as ebb & flood, flood & drain, and subirrigation, this method of hydroponics features a growing tray(s) that is situated above a nutrient reservoir, incorporating a fill and drain fitting attached to a pump in the reservoir with black vinyl tubing. The pump is in turn attached to a timer, which activates the pumps, forcing the nutrient solution into the growing tray for short periods of time several times per day. After the short feeding period, the pump shuts down, allowing the nutrient solution to drain back into the reservoir via gravity for use in the next irrigation cycle, pulling oxygen through the plant root systems as it drains.
Another variation of ebb and flow hydroponic systems incorporates individual 5 gallon buckets that are attached via pump to a large separate reservoir that floods the buckets in a manner similar to tray irrigation described above.
The plants are grown in stonewool growing cubes, or individual pots filled with an inert hydroponic growing media such as coir fiber, perlite, fired clay pebbles, and others. Since the roots are directly “spoon fed” a nutrient rich solution, root systems tend to stay more within the confines of the growing media, which many claim leads to faster vegetative and fruit production.
Passive | Deep Water Culture DWC | Raft | Hydroculture
With many variations, passive hydroponic systems operate on the mutual principle of plants growing so that the roots are constantly submerged in a reservoir of continuously oxygenated nutrient solution. Any hydroponic system where the roots are growing directly into the nutrient reservoir without any active assist from a water pump can technically be termed an passive system.
In Deep Water Culture, or DWC, plants are grown suspended over a reservoir, typically a five-gallon bucket, in which an airstone attached to an air pump continuously oxygenates the nutrient solution. A newer sub-variation of DWC is known as Recirculating Deep Water Culture (RDWC). This implementation connects all of the aerated growing buckets in a single system together, recirculating the nutrient solution contained collectively in the individual buckets throughout the entire system.
In the Raft variation, plants are cultivated on a floating bed, typically constructed of styrofoam, that floats directly on top of the nutrient reservoir, which again is oxygenated with the assist of an airstone or similar device.
In Hydroculture, plants are grown in individual fully closed pots that contain very shallow levels of nutrient solution, and usually of a weaker strength. The plants are most commonly supported with an inert clay pebble media. Ideally suited for houseplants and plantscaping applications, hydroculture is a popular soilless method of growing houseplants in Europe.
Drip Irrigation | Tower | Column Culture
Drip irrigation hydroponic systems bring nutrient solution from a centrally located reservoir via a network of drip tubes or emitters to feed individual plants growing in a pot, growing cube, growing slab, or growing bag filled with inert hydroponic media, the excess drainage of which is collected again in the reservoir. In the tower variation, the drip tubes are attached to the top of a vertical growing tube containing an inert hydroponic media with plant growing sites strategically positioned around the tube.
A variation of the drip irrigation method is known as Drain to Waste… wherein the nutrient solution is not collected and recycled in a reservoir, rather the nutrient solution is only utilized once, being allowed to drain through the growing container to be absorbed into the ground.