Nutrient Film Technique (NFT)

Nutrient Film Technique (NFT)

Nutrient Film Technique (NFT) is a growing system where your plants grow in a shallow ‘film’ of moving nutrient solution, using very little or no growing media. Plants are grown in tubes called gullies or in grow tanks in order to increase the space needed for root growth.

Nutrient Film Technique (NFT) System Illustration

An NFT system uses a pump to deliver nutrients to the plants roots, which grow into the gullies. To ensure the nutrients flow back to the reservoir for
re-circulation, the grow tray or gully is placed at a slight angle to create a natural slope. There is no need for a timer as the always-on pump supplies a constant flow of nutrients over the roots. The reservoir is kept aerated by an air pump, attached to an air stone. This prevents the nutrient solution from settling and supplies the roots with oxygen.

Benefits of Nutrient Film Technique

Minimal water and nutrient required

With Nutrient Film Technique you only have a “film” of water that is maintained at two to three millimetres deep. This continual flow of nutrients runs along the base of the gullies, directed where the root system sits. Nutrient Film Technique works with most of the root mass sitting in the nutrient solution, with some of the higher roots remaining exposed to the moist air, accessing sufficient levels of oxygen. NFT systems also allow you to grow using significantly less water and nutrients, which is more sustainable both economically and environmentally.

No need for a growing medium

Seedlings or young plants in Nutrient Film Technique systems are typically supported by either propagation cubes of rock wool, or small lattice pots, which slot into the top surface of the growing channels. Pots sometimes include clay pebbles or perlite. No other medium is required, which makes this a convenient and easy system to set up.

Easy to check root health and treat any disease issues disinfect roots and setup

Because of the lack of medium involved, plants can easily be lifted out of the system and visibly checked for disease. If any issues are found, they can
quickly be disinfected and replaced in the system. Likewise any roots that look diseased or dead can be trimmed and then replaced with little impact on the rest of the mass.

Non-stop flow prevents salt build-up

As the water in an NFT is being constantly pumped around to keep the majority of the root mass wet, the chance’s of nutrient salt build up in the root area is dramatically reduced.

Top Tips Using Nutrient Film Technique (NFT)

Wait till your plants are truly ready before transplanting

Wait until roots are bursting out of your starter blocks before transplanting them into your NFT system. This is very important as if the roots are not established enough then your crop will fail! Use air-pruning techniques to really make sure that the propagation media is full of roots before transplanting.

Buy the best that you can afford

One of the main risks involved with NFT is pump failure. This is partly because the system requires the pump to operate all the time.

NFT systems are mostly medium-free, so, if the pump fails, or the power supply is interrupted, roots quickly dry out. This can kill a whole crop within hours. The lesson here is to buy the best pump you can, to try and ensure some guarantee of pump quality.

Regular checks of equipment are essential

NFT pumps need checking regularly, to ensure that they’re running. And that the nutrient salts are not causing any build up on or around it. Avoid this by regularly cleaning and maintaining the pump and making replacements whn required. Replacement parts are relatively inexpensive. Additionally, deep clean your tanks in between crops with a soap solution and rinse thoroughly. Refresh the nutrient reservoir every 7-10 days to keep it at optimum quality.

NFT System spares are inexpensive and handy to keep for those last-minute changes of heart.

Check root health regularly

In an NFT system, your plants are prone to bacterial disease like Pythium. Slimy roots are also common. This is generally the result of a bacterial infection. Infections can originate from a range of sources, including new plants, or your water supply. Infections like this can spread quickly, infecting your whole system.

To help fix infections:

  1. Run the roots under clean water to remove the slime.
  2. Disinfect them in a hydrogen peroxide solution.
  3. Deep clean the system.
  4. Return the plant to the system.

Checking your plant’s roots is simple. Lift the NFT cover. Lifting plants once in a while also helps loosen roots, as the narrow growing channels can easily clog.

Nutrient Film Technique (NFT) System Mustard Plant Roots in Net Pot

Monitor and maintain temperature

With no growth media around the root zone there is less insulation and protection from extreme temperatures. Keeping the temperature of your nutrient solution correct therefore is crucial. 18-20oC is the best temperature to allow high levels of dissolved oxygen, resulting in optimum nutrient uptake. To achieve this, you may need to use a nutrient chiller and/or submersible heater.

Monitor and maintain pH and EC

Maintain the pH of your nutrient solution at around 5.8 – 6.2. Check regularly as it can rise as the plants feed. Inside plants, grown under lights, will absorb water at a greater rate than they take up nutrient, so over time the EC of the solution will also rise. Be sure to regularly check your nutrients with a suitable nutrient meter and replace in full when needed.

Plant the right way

If you start your plants off in 3″ rock wool cubes, make sure the ridges, at the bottom of the cube, are in line with the nutrient flow and not perpendicular to it. Sitting the ridges at 90o will negatively impact the nutrient flow, as the roots grow the wrong way in the planting channels. Also, make sure you remove the plastic wrapping, before placing your rock wool in to your NFT System. This allows the roots more access to oxygen.

Prevent light leakage

Try to avoid any light leakage by ensuring that the holes in your systems’ cover are just big enough for your plants to fit through. You should also cover the bases of your plants to prevent green algae forming, which is common when using Rock wool. Whilst relatively harmless, this algae can compete with the roots for oxygen.

Have adequate support ready

NFT is a bare-rooted growing technique. Plants can grow at speed. When they start fruiting, all but the smallest will need additional support, otherwise they will topple over.

Spreader mats

Use Spreader mats to evenly spread water across all the channels. You should only use one layer, more than that can slow the water flow and restrict growth. When cutting lengths of spreader mat, make them long enough to allow an overhang of a few inches from the channel into the tank to eliminate any trickling water sounds!

NFT is an advanced growing system. If you take care and follow a few simple steps, like the ones above, there’s no reason why you can’t use it successfully and produce huge yields.

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