Nutrient Film Technique

Ultimate Guide to Nutrient Film Technique Hydroponic System

Hydroponic Nutrient Film Technique System

In hydroponic nutrient film technique (NFT) system, nutrient solution is continuously pumped into the growing channel which is gently sloping to allow the thin film of the nutrient solution to cascade gently from one end to the other draining excess nutrient solution back into the reservoir. The plants’ roots are suspended in the space in the growing gully with the film sweeping beneath the roots.

The flowing nutrient solution passes beneath the roots dampening and giving them an opportunity to absorb dissolved nutrients and water

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

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

Materials required in building a hydroponic nutrient film technique (NFT) system

Setting up your own hydroponic Nutrient film technique system materials required include:

Solution reservoir

Choose a reservoir tank that is lower in height than the growing gullies and make it light-proof to prevent algae from growing in the nutrient rich solution.

Growing gullies

In Nutrient film technique systems, the growing table serves as a channel for the nutrient solution circulation. Ideal NFT growing gullies have a slightly flat floor with longitudinal grooves to allow efficient flow of nutrient solution in the gullies. In homemade simple setups, the widely available 2 inch PVC pipes could be used as gullies. In choosing the channels, you should avoid material made with heavy metals. Remember to buy a 2” PVC end cap that fits on the pipes.

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. The folding trellises are designed to allow vertical expansion by adding more growing channels stacked on 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.
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 pumps air into the submerged air stone which in turn diffuses the air bubbles evenly to 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 needs of different crops.

Growing net pots

These are growing pots which hold and support the crops on the gullies. The size of the pots depends on the type of crops you intend to plant.

Hydroponic nutrients

These are either organic or non-organic premixed fertilizers and trace elements that are essential for plant growth. The type of nutrients added depends on the type and requirements of a particular crop. The grower is also at liberty to choose if they want to pursue organic farming by adding organic nutrients or otherwise.

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.

Controller 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 cutter and hack saw for cutting PVC
  • Rubber grommet
  • 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

  1. If the solution reservoir is transparent, paint it black leaving a transparent vertical line for monitoring nutrient solution levels. Drill two holes on each end of the lid of the reservoir. One inch hole is for air line from the air pump to the air stone and electric cord to the submersible water pump. The other hole is for the inch tubing is delivering the nutrient solution from the pump to the growing channel. Cut out another hole in the lid for the drain line from the grow tray. The drain line holes can be as many as the drain pipes.
  2. Using a drill cutter, drill 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 just sit in without falling through into the channel.
  3. Using a hack saw cut the PVC pipe to an appropriate length. 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.
  4. Using PVC hangers, suspend the gully on the unfolding trellis. 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 saluting by adjusting the slope gradient accordingly.
  5. 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.
  6. 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.
  7. Fill the nutrient reservoir with the hydroponic nutrient solution up to the recommended levels. Test the pH and adjust it accordingly.
  8. 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.
  9. 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.