The nutrient film technique or NFT is popular among commercial growers because of its versatility and aggressiveness. NFT consists of long grow chambers such as a PVC pipe. Along the pipe, there are holes holding the net baskets. The roots of the plant are suspended in the pipe, then a shallow stream or “film” of nutrient-rich water flows across the roots. Common setups can consist of a piece of gutter. Roots lay flat along the bottom of the gutter, and a slow constant trickle of nutrients flows to the end.
The NFT system is very similar to the Ebb and Flow—the difference is their setup. Like the Ebb and Flow, the system uses a pump to deliver the nutrient solution to the grow tray and a drain pipe recycles what is unused. Except with the NFT, the nutrient solution is always flowing over the roots. This is carried out using gravity. The PVC pipe or gutter are placed at an angle to allow the water to flow down towards the drain pipe. The unused nutrient solution is then pumped back to the top of the system.
PVC pipes or gutters have the advantage of being cheap and readily available. The main disadvantage of this channel is that the film may not fully coat the root system. You can end up having the roots that fall towards the center of channel getting much more nutrients then roots that may grow up the sides. That is why using a flat channel, like a gutter, solves this issue because the root system will then grow flat and the nutrient solution can fully coat it.
Something else to think about is the length of the channel. As the nutrient flow down your channel and the roots soak up these nutrients, the root systems towards the end of channel will receive as less nutrient rich solution. Shorter channels will allow the roots systems towards the end of the channel to receive a nutrient solution with the same composition as those at the beginning of the channel. Longer channels can still work successfully. It is just takes extra maintainence to make sure the nutrient levels are stable throughout the channel.
Stability is important!
Most NFT systems will not use a growing medium, as filaments can cause blockages along the channel. Unless something like coconut husk is used where the growing medium can be molded into a kind of net basket which offers the optimum stability for the root systems. Whichever way you choose to plant, it is important to trim the roots often as they can also lead to blockages and poor weight distribution along the channel.
Nutrient Film Technique also works best if you choose stable plants that do require a lot of weight lifting. So, vining plants are not recommended as you will need to attach a support structure surrounding the grow channel. Instead, leafy greens and herbs make the perfect plant to grow in this system as they tend to grow in bunches and do not require much support.
Although there are not any misters that can clog, there is still truly little liquid for the roots. This means if the pump shuts down for an extended period, the roots will begin to dry out quickly. With careful monitoring, however, an NFT system can easily be set up in a basement or garage and yield delicious leafy produce.