Hydroponic growing techniques

Nutrient Film Technique

The purist form of today's highly developed hydroponic growing systems is Nutrient Film Technique (N.F.T.). It is also the form of hydroponics most intriguing to the public because of its futuristic nature and appearance.

The nutrient is fed into grow tubes where the roots draw it up. The excess drains by gravity back to the reservoir. A thin film of nutrient allows the roots to have constant contact with the nutrient and the air layer above at the same time.

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Nutrient solution is re-circulated through an extruded plastic channel by a pump submersed in the reservoir, providing plant roots with a constant supply of fresh water, nutrient and oxygen.
The top of the roots are exposed to air. The bottom of the roots are exposed to the nutrient solution.
NFT is most often used in commercial lettuce production.

Examples of N.F.T. growing systems are the Hydro Harvest gardens.

Drip-Irrigation or Micro-Irrigation

Today's greenhouse irrigation systems employ, to an ever-increasing extent, the concept of drip or micro-irrigation. It entails a principle of minimized water consumption with maximized plant benefit. There are literally hundreds of emitting/dripping/trickling/micro-spraying/etc. devices on the market today for the commercial/hobbyist grower to choose from.

A submersed pump feeds nutrients solution through header tubes to secondary feed lines connected to drip emitters.

A controlled amount of solution is continuously drip-fed over the medium and root system. Another tube is connected to the lower part of the garden system to recover the solution.

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Nutrient solution is delivered to the plants through drip emitters on a timed system.
The timed cycle flushes the growing medium, providing the plants with fresh nutrient, water and oxygen as the emitter is dripping.
In a drip system, the plant roots are usually grown in a medium of perlite or rockwool. The drip system is often used by commercial growers for tomatoes, cucumbers and peppers.

Examples of Drip-Irrigation systems are the Expando Gardens.

Aeroponics / Deep Water Culture

Plant roots are suspended in highly oxygenated nutrient solution allowing easy inspection and pruning of roots. Air pumps, compressors or Oz injectors provide oxygen which is crucial to healthy plant growth. The simplicity and affordability of these very active systems make them popular with home hobbyists and commercial growers alike.

In an Aeroponic system the roots are misted within a chamber. A pump pushes the water with nutrient solution through sprayers, keeping the roots wet while providing a maximum amount of oxygen.

This technique is an excellent way to propagate cuttings.

Deep Water Culture is another form of aeroponics. The root system of a plant grown in Deep Water Culture is immersed in water with a bubbling aerator keeping the roots oxygenated.

This technique is very good to use with plants that are heavy feeders.

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Plant roots are suspended in highly oxygenated nutrient solution allowing easy inspection and pruning of roots.
A small aquatic air pump provides oxygen which is crucial to healthy plant growths.
The simplicity and affordability of these self contained systems make them popular with home hobbyists.

Examples of Deep Water Culture gardens are ‘Jack’s Gardens’.

Flood & Drain

Flood & Drain systems are similar to N.F.T. systems. They are ideal for multiple plant per square foot growing where individual plant inspection is difficult. They are also very popular as propagation tables.

A plastic growing tray is flooded periodically by a submersed pump connected to a digital timer (or the ControlFreak!). Medium and root system are soaked, then drained (via gravity back through the pump) at specific intervals.

Various mediums can be used, Rockwool is the most popular with Flood & Drain systems.

The Ebb & Flow trays are examples of the Flood & Drain system.

Home Hobbyist Systems

There are a number of compact hydroponic systems and kits most popular with home hobbyists, researchers and teachers. These are made to be especially attractive to children in order to get their attention and interest. Hobby systems include deep water and aeroponic systems which are scaled down versions of commercial systems.

An example of a Home Hobbyist System is 'The Garden That Jack Built'.

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Passive Planters / Hydroculture

This is probably the most commonly know form of hydroponics. These systems do not require a water or air pump and are therefore called passive systems. Passive Planters have been used in office buildings and restaurants for many years.

Hydroculture planters utilize a clean, porous growing medium to support plant roots. A nutrient reservoir in the base of the growing container allows the plants to take as much or as little water as they require. Water level indicators show exactly when and how much to water. Clean, odourless and non-allergenic, hydroculture or passive planters are ideal for every environment.

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Plants are anchored in a growing medium which provides capillary action for nutrient solution contained in an outer shell. A water level indicator monitors nutrient levels to ensure a good nutrient to oxygen ratio is achieved.
Passive hydroponics requires little maintenance and does not use pumps or timers. This method is ideal for tropicals or ornamentals as plants grow slower than in other systems.

Examples of Passive Planters are Hydroculture and Self Watering Wick Systems.

Additional information:

Read the book: "Hydroponic Food Production" by Howard M. Resh

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