Ultimate Guide to Nutrient Film Technique Hydroponic System

Nutrient Film Technique

Hydroponic Nutrient Film Technique System

In a hydroponic nutrient film technique (NFT) system, nutrient solution is continuously pumped into a growing channel, called a gully, which is gently sloping. This allows the thin film of the nutrient solution to cascade slowly from one end of the channel to the other over the bottom roots of the plants.

Excess nutrient solution drains back into the reservoir at the opposite end of the channel. The plant’s are suspended above the growing gully with the film of nutrient solution sweeping over the lower root sections and allowing the upper roots to absorb oxygen from the air.The flowing nutrient solution passes beneath the roots keeping them moist and giving them an opportunity to absorb dissolved nutrients from the water.

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NFT Design Advantages

The NFT hydroponic design is a closed system which saves and reuses the same nutrient solution in a constant cycle. This makes it a very efficient and simple system to operate using less water and nutrients than many other hydroponic systems.

An NFT hydroponic system does not require a timer for operation and because the water movement is slow it does not take a large pump to supply the nutrient solution to the system as long as the gullies are within a foot or two above the reservoir.

Air stones and air pumps can be integrated into the system but are usually not required because the water is constantly moving and oxygenating itself as it splashes around. Most systems don’t use a grow media either, instead they just allow the roots to support the plant within the net cups.

Commercial grow gullies have fine grooves on the flat bottom, the grooves allow nutrient solution to flow continuously underneath the roots despite the root thickness.

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Growing Applications

Since the roots are continuously bathed by the nutrient film, some crops can rot away due to overfeeding and water logging. NFT hydroponic system is best suited for quick-growing plants such as different types of green vegetables like lettuce, baby greens, and other types of herbs.

Fruiting plants take longer to mature and grow a substantial root system that can block up the growing channel of an NFT system causing many different issues. For larger plants choosing a different type of hydroponic system is recommended. See our guides to Ebb and Flow Systems, Deep Water Culture, and Drip systems for more information.

Components of a hydroponic nutrient film technique (NFT) system

Setting up your own hydroponic nutrient film technique system requires the following materials:

Solution reservoir

Choose a reservoir tank that is lower in height than the base that support the growing gullies, this will allow the extra nutrient solution to drain using gravity. Also make sure the reservoir is not transparent to prevent algae from growing in the nutrient rich solution.

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Growing gullies

In Nutrient Film Technique systems, the growing table is created using long channels (called gullies) which guide the nutrient solution to flow over the plant’s lower roots. Ideal NFT growing gullies have a flat floor with longitudinal grooves to allow efficient flow of nutrient solution in the gullies.

In homemade simple setups, widely available 2 inch PVC pipe or square PVC downspout can be used as gullies. When choosing the channels, you should avoid material made with heavy metals and look for UV resistant food grade materials.

Supporting trellis and PVC hangers

These are supporting structures that hold the growing channels on a higher level above the reservoir to allow free gravitational flow. Many trellises are designed to allow vertical expansion by adding more growing channels stacked above each other.

Submersible water pump

This is an electric pump used to pump the nutrient solution to the growing gullies. The size of the water pump depends on the length of the growing gully or number of grow gullies. Selecting a pump with an adjustable flow rate will allow you to dial in the best flow for your setup.

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Air pump, air line, and air stones

These are optional additions in the NFT hydroponic system used to add oxygen into the nutrient solution and can be found in any aquarium stores around you. The external air pump supplies air into the submerged air stone which in turn diffuses the air into bubbles to evenly distribute oxygen throughout the solution. The size of the air pump and the number of air stones needed depend on the amount of nutrient solution in the reservoir and the needs of different plants.

Growing net pots

These are growing pots which hold and support the crops in the gullies. The “netting” of the pots allow the roots to easily exit out of the bottom and sides of the pot and extend down to the bottom of the gullies to absorb the nutrient solution. The size of the pots depends on the type of plants you intend to grow and grow media used.

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Hydroponic nutrients

These are either organic or non-organic premixed fertilizers and trace elements that are essential for plant growth. The type of nutrients used depends on the requirements of crop you are growing. As the grower it’s your choice on whether to choose organic nutrients or traditional synthetics.

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Delivery tubing

These are half-inch vinyl hose pipes used for delivering the nutrient solution from the water pump to one end of the grow gully. You should also include a half-inch drainage pipe for draining off the excess solution from the other end of the gully back into the reservoir. The number of the pipes should correspond to the number of grow gullies.

Monitoring tools

Thermometers and pH test kit are essential in maintaining a conducive environment for nutrient and oxygen absorption.

Other tools needed in the assembly of the NFT system include:

  • Drill and hack saw for cutting PVC
  • Rubber grommets
  • PVC glue used for connecting the pipe network
  • Tape measure

Step by step guide on setting up a simple hydroponic Nutrient film technique (NFT) system

  • Drill a 1″ hole at each end of the lid of the reservoir. One hole is for the air line from the air pump to the air stone and electric cord to the submersible water pump. The other hole is for the tubing delivering the nutrient solution from the reservoir to the growing channel. Cut out another hole in the lid for the drain line from the gullies.
  • Using a drill, make holes along the PVC pipe spacing them accordingly to give your crops enough room to grow. The holes should be cut out into the appropriate size for the net pots to sit in without falling through into the channel.
  • Using a hack saw cut the PVC pipe to the appropriate length of your system (typically 4-6ft). If the grow channels are too long, the nutrient in the solution film gets diminished on the way so that crops on the end of the channel receive lower amounts of nutrients. In a short channel (4-6 feet), relatively equal amounts of nutrients in the solution are delivered to all plants in the gully.
  • Using PVC hangers or some stands, support the gully evenly along its length. The channel should be placed in a gently sloping gradient to allow free flow of the nutrient film. The PVC hangers on the trellis are adjustable giving you the control of the flow rate of the solution by adjusting the slope gradient accordingly.
  • Drill a 3/4 inch hole in the PVC end caps. The hole is higher on one cap than the other. Using a rubber grommet attach one end of the delivery vinyl tube to the end cap; use PVC glue to seal the joint. Remember the delivery tube connects to the cap with the higher-placed hole while the draining tube connects to the cap with the lower-placed hole. The lower the hole on the delivery end cap, the lower the height of nutrient solution in the channel. Using PVC sealant, cap off both sides of the channel accordingly.
  • Add supporting medium such as rock gravel or sea pebbles in the net pots, place a single plant in each of the pots and place them in their designated holes in the growing gully.
  • Fill the nutrient reservoir with the hydroponic nutrient solution up to the recommended levels. Test the pH and adjust it accordingly.
  • Connect the air pump to the air stone and submerge it. Make sure the air stone is releasing air bubbles evenly before closing the lid.
  • Connect the water pump to the delivery tubes and place it in the solution. Switch on the power source to the water pump to kick start your system.

In NFT system, the flow rate of the nutrient solution and the slope gradient of the grow channel are major factors on nutrient delivery and overall efficiency of the system. The recommended slope of the grow gully is 1:30 to 1:40 ratio, that means 1 inch in vertical drop for every 30 to 40 inches horizontal length. It’s recommended that in designing the system, the slope should be adjustable while plants are growing so as to keep up with the growing roots and avoid stagnation.

image source Hanna Instruments
image source Hanna Instruments

Maintenance of hydroponic NFT farming systems

The entire system needs to be enclosed to prevent sunlight from hitting the plants’ roots directly.

  • The nutrient film nourishes several crops along its flow channel. Therefore, the crops near the delivery end are bathed with a higher amount of nutrients which diminish along the way as they are absorbed by the crops. This leads to some crops being underfed. Ways of avoiding under feeding of some crops in the system include installing shorter gullies to cut the flow distance or adding more delivery further down a channel.
  • Monitor the solution and refill accordingly. Since it’s a circulating system, nutrients in the solution gets diminished over time. Therefore, it is advisable to drain and flush the system, clean the reservoir and refill the chamber with fresh solution every so often (after every 7-10 days).
  • Since the solution film runs along the roots, the channels are subject to blockage which can leave to poor production. Regular monitoring of the root growth is important to avoid clogging.
  • Since NFT system relies so much on external power output, prolonged power outages or rationing can starve the crops off essential nutrients. This shouldn’t affect you much as a small beginner, but large commercial systems need an automatic alternative power source such as a generator.