NFT(nutrient film technique) is running solution along a surface via gravity for which the plants suck up nutrient. It is very common to grow lettuce this way. The big advantage of NFT is ease of use because it does not require too much setup and needs only a single feeder line for each row of pipe.
NFT (Nutrient Film Technique)
With nutrient film technique, plants can be fed with continuous or intermittent film that is pumped through a header line, then drained down a trough, PVC pipe, or flood table. The solution travels down the bottom of the trough where it collects in the reservoir, before it is recirculated. The solution can run all day.
Capillary matting can be placed under trough.
Air pumps can be used to aerate the nutrient solution.
Automatic thermostatic heat cords can be placed around a reservoir to keep the solution warm. Chillers cool the reservoir.
The only difference in building this system from the top-feeding system on pages 29 to 33 is the header line. The 1/2-inch poly or PVC header line runs along the side, then it connects to a matching elbow. Then it runs along the back of the pipes until it reaches the end.
The header line is end-capped at the end. Only one feeder line is connected to the header line on each each pipe to deliver the solution down the pipe.