First developed in the 1970’s in England, the nutrient film technique is the only hydroponic system that uses constantly flowing liquid to feed and water plants.
Although its name may sound a little technical, it’s actually quite a simple system to set up and manage, and is flexible enough to scale up should you ever want to include more plants in your system.
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What is the Nutrient Film Technique (NFT)?
The nutrient film technique is a hydroponic growing method that uses a continuous stream of nutrient solution to nourish plants.
The stream is shallow enough to allow the top half of plants to stay dry and absorb oxygen, but deep enough for the roots of the plants to stay constantly submerged.
How Does the Nutrient Film Technique Work?
The nutrient film technique makes use of a tube-shaped growing chamber that’s placed at a slight angle – this allows gravity to draw the nutrient stream through, after it has been pumped up from a reservoir that sits just underneath the growing chamber.
Many NFT systems actually make use of multiple chambers, as a single chamber can be quite restrictive in terms of how many plants you can comfortably fit inside.
Since the roots of each plant are always submerged in the nutrient solution, a growing medium isn’t needed. In fact, using a growing medium in a NFT setup could leave your plants susceptible to rot, and is only advisable when starting with very young seedlings.
Instead, the plants are placed into a net pot, which is then inserted into holes that run along the top of each growing chamber.
This allows the roots to reach into the chamber, while allowing the leaves of the plant to absorb oxygen from the air.
Once the nutrient solution reaches the end of the chamber, it flows back down into the reservoir, where it is then recycled by being pumped back up to the highest end of the chamber.
Let’s see how Nutrient Film Technique (NFT) system runs:
Pros and Cons of Nutrient Film Technique
Pros:
- Simple and basic to set up and maintain.
- Cheap to run.
- It’s adaptable in terms of size, meaning that NFT works even in small spaces.
- Nutrient flow is constant, so you don’t need to worry about timers.
- Nutrient levels can be precisely controlled.
- The system requires very little maintenance.
- The way a NFT system is set up makes it easy to check on the roots of your plants to ensure optimum plant health.
- With a consistent water flow, salt and mineral build-up isn’t usually a problem.
- The constant flow also means that pH levels stay relatively stable.
- NFT doesn’t require the use of any type of growing medium.
- Since the water is constantly flowing, it stays aerated and doesn’t go stagnant.
- NFT growing reuses both nutrients and water, making it highly efficient and environmentally-friendly.
Cons:
- Nutrients can become quite depleted by the time they reach the end of the chamber.
- Electricity is required 24/7 in order to run the pump. If electricity supply ever stops due to a power cut or anything else, even for a very short period of time, this will seriously affect the health of your plants – it could even be fatal.
- NFT growing isn’t suitable for large plants with extensive root systems, since there’s a limited amount of space inside the growing chamber.
- Plants that need supports in order to grow are also not suited to the NFT system.
How to Build a NFT Hydroponic System (Setup)
Compared to some of the other hydroponic systems out there, NFT is pretty easy to set up.
What You Need for a NFT System:
Growing chamber:
This should ideally be flat, rather than curved, at the bottom, as this gives the roots of your plants a larger surface area to feed from – square PVC pipes work well.
Chamber length can vary but 10 meters is the longest you should go – any longer than this and the plants that sit at the bottom end of the chamber will end up severely deprived of nutrients, since all of the plants higher up would have depleted these from the nutrient solution.
Net pots:
These are small baskets that hold each plant, doing away with the need for a growing medium. In terms of size, they need to be large enough to comfortably accommodate each plant as it grows, but small enough to fit through the holes that you make in your growing chamber.
Reservoir:
The size of this is completely up to you – the larger your reservoir, the less often you will need to top it up.
However, make sure that you pick something made from an opaque material, as this minimizes the formation of algae.
Tubing:
Your tubing needs to be long enough to connect your reservoir to the highest point of your growing chamber. While some growers also use tubing to bring water back down to the reservoir from the growing chamber, you can set this section up in a way that doesn’t require this.
Pump:
Your pump doesn’t need to be complex – a simple, low-volume submersible pump is all you need. However, you may want to opt for one that allows you to adjust the flow rate, as your plants will need varying volumes of water and nutrients as they grow.
Nutrients:
The exact nutrients you need will vary depending on the type of plants you are growing.
If you’re concerned about a lack of oxygen in your nutrient stream, then you may want to consider adding in an air pump and some air stones.
Although not a necessity, these help to aerate the water even further, ensuring that oxygen is evenly dispersed through the nutrient solution.
Building Your NFT System
To start with, you’ll need to drill three holes into the top of your reservoir. These are for:
- The cord for your pump
- The tubing that runs to the growing chambers
- Drainage that runs from the growing chambers to the reservor
Then, make some holes in your growing chambers – these need to be large enough to hold the net pots you plan on using, without risking the chance of the net pots falling through into the chamber.
This is also the time to decide on the length of your growing chambers. Remember, the shorter your NFT channels, the more nutrients your plants will receive.
Then, make a hole at either end of your growing chamber – the higher the hole, the higher the level will be of the nutrient solution that runs through.
Set your growing chamber at an angle above your reservoir – stands can help to support its weight. Place your plants into net pots and then insert these into the growing chamber.
If you don’t have enough plants to fill all of the holes that you have made, seal up the extra holes, even if just temporarily. This prevent light from seeping in, which would otherwise trigger the growth of bacteria.
Add your nutrient solution to the reservoir, making sure that you check and adjust the pH level. Temperature is important too in order for your plants to receive the maximum amount of nutrients – around 20°C is ideal, but keep in mind that the temperature will likely be higher to begin with, until the constant flow of water cools things down.
Finally, connect up your pumps and your tubing. After this, all you need to do is turn on the electricity to your pump and you’re good to go!
This guy will show you how he builds his Nutrient Film Technique (NFT) Hydroponic system:
Adjusting the Angle of the Growing Chambers
The gradient that your growing channels slope at is crucial when it comes to how well your NFT system works. The angle you use determines your flow rate, which has a direct effect on the amount of water and nutrients your plants receive.
The flow rate can vary depending on the plants you’re growing, but, to start with, aim to have a flow rate of around 1 liter per minute. This usually works out to a gradient ratio of around 1:30, meaning that for every inch in height, you will need 30 inches of chamber length.
In addition to adjusting the angle of your NFT channels, there are a few other ways in which you can modify the flow rate of your system:
- By adding drains that you can adjust to the bottom of each growing chamber.
- By using a pump that allows you to manually adjust how much water is flowing through.
- By inserting inline valves into your growing chambers.
Getting the flow rate right can take some time, and may also need to be adjusted again as your plants grow. The larger the root system, the stronger your flow rate should be – if you don’t adjust this, the roots of your plant may end up blocking the flow of water and nutrients through the chambers.
However, don’t be tempted to go with a faster flow rate at the start. This can cause nutrient deficiencies in your plants, since the water will be flowing too quickly for young roots to be able to absorb up all that they need.
Maintaining a NFT System
Maintenance is pretty easy with the hydroponic nutrient film technique, but there are still a few things that you will need to do:
- Top up your nutrient solution whenever it starts to run low.
- Keep checking nutrient levels – the more your plants consume, the lower these will get, even if the water level doesn’t seem to have changed much. You will probably need to fully drain and flush your setup every week or so.
- Clean and sterilize your reservoir once a week – this can be done at the same time as the draining and flushing.
- Regularly check your growing chambers to ensure that it is not being clogged up by roots.
- If power outages are common in your location, you may want to consider an alternative power source as a backup.
Best Plants for NFT System
As efficient as the NFT system may be, it’s not suitable for all plants.
Since the growing chamber is quite restrictive, plants that have large root systems won’t have enough space to properly grow. Certain plants also end up rotting when constantly sat in water, meaning that you need to choose your plants carefully.
If using an NFT system, pick fast-growing plants that can be harvested while they’re still quite small and young, before their roots end up filling the growing chamber – if this happens, the nutrient solution will be blocked from flowing properly.
Some plants that work well in a NFT system are:
- Lettuce
- Leafy greens, such as spinach
- Herbs
In addition to avoiding large plants, you should also stay away from fruiting and flowering plants when using a NFT system. There are two reasons for this:
- Fruiting plants require a large amount of nutrients. This means that the nutrient levels, as well as the pH level, of your nutrient solution will be constantly fluctuating and will need constant monitoring.
- Both fruiting and flowering plants don’t do well when their roots are constantly submerged in liquid. They need some time to dry out in between waterings in order to thrive.
Summary
Fast-growing plants really do thrive in a nutrient film technique system, making this the setup of choice for many growers.
Although it definitely takes some experimentation at first to get things running optimally, this easy and low-maintenance system is perfectly suited for both beginners to hydroponics as well as commercial growers.
