What is the Hydroponic Nutrient Film Technique?
Nutrient Film Technique, or NFT, is a popular and versatile hydroponics system. It is similar to Ebb and Flow in that the system uses a pump to deliver fertilized water to the grow tray and a drain pipe to recycle the unused nutrient solution. The difference is that in NFT the nutrient solution is continuously flowing over the roots. This is accomplished using gravity. The grow tray is placed at an angle to allow the water to flow down towards the drain pipe, and new solution is constantly being pumped into the high end of the tube. NFT is an active system, meaning it relies on moving parts to work. Passive systems such as Wick Systems have no moving parts.
The nutrient solution flows in a thin film over the roots, ensuring that they are watered and fed but not completely soaked. The thin film ensures that the upper part of the roots will remain dry and have access to oxygen in the air.
Nutrient Film Technique works best if you choose plants that do not require a lot of support- light weight, fast growing plants that can be harvested quickly. The roots are not suspended in a growing medium in this system, so they cannot handle supporting a lot of weight from a top-heavy plant.
The main components of an NFT system are the same as Ebb and Flow- the difference is their configuration.
The Grow Tray
Nutrient Film Technique uses tubes or channels instead of flat trays for the grow tray. This makes it easier to set it at an angle and to make sure that the nutrient solution flows directly to the roots without wasting any of it. Most often in DIY systems, a round tube or PVC pipe is used, with holes drilled to fit the net pots and seedlings.
You can either place seedlings directly into the holes of your PVC pipe or channel, or for greater stability plant them in net pots and place the net pots in the holes. Most people do not use a growing medium with NFT, but let the roots fall directly through the net pots and on to the film.
The reservoir is placed under the grow tray, connected to the channel by a pump on the high end and a drain tube on the low end. You must also place an air stone in the reservoir, connected to an air pump outside, to oxygenate the water. Unlike other systems, the NFT does not use an automatic timer connected to the water pump because the pump runs constantly.
D'Anna, Christina. "Hydroponics: How to Use the Nutrient Film Technique." About.com. Web. 31 Aug. 2014.
Diagram of a Nutrient Film Technique System. Image © Christie D'Anna
Image from downtoearthkent.wordpress.com