What Is Nft Hydroponics?

by Lettuce Be | Last Updated:

The nutrient film technique is a type of recirculating hydroponic system. This hydroponic design is named for the very low-flow irrigation that nourishes the plants within the system. A thin “film” of nutrient solution is continuously present by slowly pumping water into a flat channel. 

NFT: How Does It Work?

nutrient film techniqueThe NFT works on the principle of a thin film of liquid running through the system. Through contact with the film, root systems can absorb nutrients without sacrificing aeration. It is possible to produce impressive yields with little effort if you balance water flow, nutrients, and oxygen in the system.

  • A flat channel, somewhat like what would be found on your house’s roof, is angled at just the right angle. 
  • There are holes drilled in the channel’s top so that you can place seedlings into net cups. 
  • Pumps send nutrients up the channel where they flow by gravity down, contacting the plant roots as they do so. 
  • Where the water drains down into the reservoir, it returns to its original location.

An NFT system is similar to an ebb-and-flow system, except that the irrigation runs constantly, and only a thin film of water can drip through the channel.

Most NFT systems don’t need air pumps or air stones. NFT is all about keeping a bare minimum amount of water flowing through the channel to give the roots ample opportunity to absorb oxygen. 

Magic happens in the space inside the channel. Many growers flood their NFT channels, resulting in a reduction in oxygen supply to the plant. For this reason, the system is equipped with air stones, and air pumps to restore adequate oxygen levels. 

When the nutrient film technique is applied with an excessive amount of water flow, it becomes a modified ebb-and-flow system that misses the point of the technique. Even though air stones and pumps won’t harm your system, they are unnecessary costs that can be avoided by simply adjusting the water flow. A tricky part of NFT is correctly determining the curve slope, channel length, and flow rate. 

In an NFT system, which plants do best?

Almost anything can be grown in hydroponics, but the question is what you should grow. Ultimately, efficiency and convenience are the most important factors. The most common crop grown with NFT systems is leafy crops, such as lettuce, spinach, bok choy, and kale. Under constant irrigation, these plants thrive.

Conversely, certain fruiting plants such as tomatoes, peppers, and cucumbers do better when water is carefully limited. In addition, because no growing media, other than some Rockwool, is used, larger plants will not grow in an NFT system. There will be no way to grow a large tomato plant in a system like this without some trellis or support to keep it upright and supported.

What are the steps to setting up an NFT Hydroponic System?

NFT systems can be built at home by anyone – simple setup and affordable materials make this possible. Various materials and configurations can be used to customize this system. 

The following materials are needed:

  • 2 PVC end caps
  • 3-inch net cups
  • 4-inch PVC pipe
  • Plastic tote (5-gallon)
  • Scrap wood (2×4)
  • Water pump
  • ½-inch poly tubing

NFT Hydroponics: Step by Step

  • Cut your PVC pipe to the appropriate size. It can be as short as you want, or around 30 feet if you wish. You’ll use it as a channel.
  • One of the caps should have a half-inch hole drilled into it.
  • On the top of your PVC pipe, drill or cut a series of 3-inch holes about 8 inches apart. Your plants will grow here.
  • On the opposite side of the holes, you just cut, drill a half-inch hole in the PVC pipe.
  • Put the end caps on.
  • The lid of your plastic tote should have two half-inch holes drilled into it, one on the left and one on the right. Put the water pump in the tote.
  • Cut your scrap 2×4 into two sections of 6 inches. Cut a “V” into each one. Your PVC pipe will be held in place by these grooves. Make one of these pieces slightly shorter than the other by trimming or sanding the bottom.
  • Select the location of your NFT channel. You can place it directly on the plastic tote or a nearby table or bench. Place your wooden pieces on top of the PVC pipe so that it rests securely within the grooves.
  • If it is on the drain end, the shorter wood piece will direct water toward the drain.
  • You will need a length of half-inch poly tubing long enough to connect the pump to the hole in the end cap. Connect the tubes by sticking one end into the end cap, putting the other end into the hole in the reservoir’s lid and attaching the nutrient pump to the other end.
  • Connect the small hole on the bottom of the PVC pipe to the other hole on the lid of your plastic tote with a short length of half-inch poly tubing. 
  • You should drill PVC pipe 3 inches deep with holes for seedlings in net cups.
  • Turn on the pump and add the nutrient solution.

Tip for Channel Slope, Flow Rate, and Modifications:

  • Place your seedlings in a channel with just enough slope to barely touch the bottom. 
  • Change the flow of the pump, so only a thin layer of water flows through the channel. 
  • To avoid the need for a timer, an air stone, an air pump, etc., let the nutrient water run constantly.
  • Generally, your channel’s slope runs between 1:30 and 1:40, although it could be as low as 1:100 in some cases. It is imperative to get a gradual decline in the slope of an NFT system while avoiding any pooling. 
  • Water should flow through a channel and drain at the end.

Aabout flow rates:

  • A channel longer than 40 feet may not provide enough nutrients to your plants. Nitrogen will be sucked up by the plants near the source of the nutrient solution, denying these plants this essential nutrient.
  • This results in the plants along the channel not being able to flourish properly.
  • The only thing you need to do is keep the channels below 40 feet long.
  • It is also possible to make channels as long as you like and add irrigation lines from separate reservoirs every 20 feet.
  • You should turn down the water flow on each irrigation line in your channel if you have more than one irrigation line. You still want a thin film in your channel, not twice as much water.

About air stones:

  • The NFT reservoir does not need an air stone. Some growers like to do this. NFT relies on keeping the water levels low, so the roots get enough oxygen while still interacting with enough solution to thrive.
  • When you need to add an air stone, your system is probably running too much water, essentially turning it into an ebb-and-flow system rather than a true NFT system.

NFT Pros & Cons

There is good reason for the wide use of the nutrient film technique, but it doesn’t accomplish everything. You should be aware of a few limitations. 

Pros

  • High water efficiency
  • Almost entirely passive 
  • Ideal for leafy greens
  • Cost-effective

Cons

  • Not suitable for fruit-bearing or large plants
  • There is a risk of spreading diseases between plants in recirculating systems
  • Your plants may be damaged or killed if your NFT system does not retain moisture during a power outage.

In an NFT system, how do you start plants?

Like any other system, you can start seeds or seedlings. 

  • You can also use a rapid rooter (or Rockwool) soaked in water or a gentle nutrient solution. Set it under grow lights or the sun in a grow tray. 
  • Put your seedlings into a net cup once they have established a strong root system and then into your Nutrient Film Technique system.
  • One must make sure the roots reach a thin film of nutrient solution at the bottom of the channel when the seedling enters. 
  • If the roots or Rockwool have not reached the nutrient solution, you can allow your seedling to grow in deep water culture, ebb and flow, or Kratky system so that the roots can grow longer.
  • Then temporarily increase the water flow until the roots or Rockwool touch the solution, instead of placing the seedling in the NFT channel. 
  • If the roots grow long enough, you should turn the water down once they are. The plants won’t have access to oxygen if you use too much water in an NFT.