The Nutrient Film Technique Explained
The Nutrient Film Technique, sometimes referred to as NFT, is one of the most popular types of hydroponic systems. It's prized for how versatile and modular it is. By adding more NFT channels to the system (I'll cover what those are later in the article), you can significantly increase your yields without too much extra effort.
How NFT Systems Work
NFT is very similar to the Ebb and Flow technique for one simple reason: they both use water pumps to deliver the nutrient solution to your plants.
In a NFT system, gravity ultimately guides the water back to the main reservoir. It's also a constantly flowing system as opposed to the flood and drain mechanics of an Ebb and Flow setup.
NFT systems are considered active systems, meaning they require moving parts to work. Systems like Wick Systems or The Kratky Method are passive, simpler to build, and easier to run, but you may be sacrificing optimal growing conditions for those benefits.
Before we go on, take a look at this simple video explaining the technique:
The key element of a good NFT system is how the nutrient solution flows over the roots. It has the word "film" in it for a reason - ideally, a very small amount of water flows through the channels. This allows the plants to get sufficient oxygen so they don't drown.
It's important to choose plants that don't need a lot of support when using a NFT setup. Lettuce, basil, and many other salad greens thrive in NFT systems, while fruiting plants like tomatoes and cucumbers require much more support. It can still be done, but it's labor-intensive to set up the support structures for these types of plants.
Benefits of NFT
Overall, a grower will use the nutrient film technique over other methods due to their low cost and maintenance requirements, as well as their flexibility. However, there are many other benefits to growing in an NFT system:
- Low water and nutrient consumption
- Avoids need to use a lot of growing media
- Easy to disinfect roots and setup
- Easy to see root quality and health
- Consistent flow prevents salt buildup in root area
- Recirculating, so minimal groundwater contamination
- Very modular and expandable
Downsides of NFT
Every type of system has its disadvantages, and NFT is no exception. Because roots are growing in confined channels, they can clog the channels. More downsides include:
- A failing pump can kill an entire crop within a few hours
- Does not work well with plants that have large tap-root systems
- Doesn't do too well with plants that need a lot of support
How to Build a NFT System
There are a million and one ways you can design a NFT system, all depending on the space you have, the plants you want to grow, and other concerns. But, there are a few materials that every system should have:
A quality reservoir is crucial to a solid NFT system. It's placed underneath your grow channels and water is pumped upwards to your channels.
When choosing a reservoir, make sure you're aware which plastics are safe for gardening. This is especially important if you're growing in full sunlight.
I recommend plastic totes from Home Depot, or 5 gallon buckets if you're setting up a smaller, hobbyist system.
Instead of flat trays like an Ebb and Flow system, a NFT system uses tubes or channels to house your plants and growing media. Many hobbyists opt for PVC pipes because they're easy to buy and manipulate. All you need is a hole saw and some net pots and you're off to the races.
The downside to using PVC is that it's a round tube. This means that your nutrient solution will not hit your roots evenly and if you've miscalculated the slope or flow rate, you might run into growth problems.
If you want to avoid that issue, you might go with rain gutters as a DIY option or even 2x4"s that are lined with a food-safe plastic sheet. But there are also plenty of products on the market that are customized for NFT growing systems as well if you want to get started quicker.
To transplant into your channels, most people use net pots and a little bit of growing medium to hold the beginning of the roots in place. Then, the rest of the roots just fall into the channel and are fed and watered via the nutrient solution running along the bottom of the channel.
When building or buying your NFT system, it's important to consider the length of your channels. The plants that are closest to the water source will get the most nutrition and oxygen, and the ones at the end will get less. For this reason, having extremely long channels may be detrimental.
Keep an eye on the plants at the end and compare their growth rate to the plants at the beginning. If you see a difference, you may need to shorten the length of your channels.
Other NFT Materials
You'll need an air pump to oxygenate the water in your reservoir. Because NFT systems also allow for a lot of air in the channels or tubes, this is less crucial than in other systems like deep water culture. But it's still recommended and pumps are fairly inexpensive.
Recommended Product: Hydrofarm Air Pump
The next logical item on the list are air stones. For NFT systems I typically like to use either an array of long thin airstones, or 2-3 of the circular airstones like the ones recommended below. These also come with suction cups, so you won't need to buy them separately.
Recommended Product: Hydrofarm Air Stone
For your tubing, it's important to get black or dark tubing. Clear tubing has the potential to incite algae growth within the tube, which isn't fun to deal with. There's no real difference in price or quality, so I opt for the tubing that will give me less headaches in the long run.
For a small system, a simple water pump like this will work just fine. If you're going to grow commercially or large-scale, you'll need something heavier duty though.
Recommended Product: Active Aqua Water Pump
Once you have all of your materials, you can set them up in a manner similar to this diagram (taken from the video at the beginning of this article):
Growing Tips For Your Nutrient Film Technique System
Control your environment. This isn't a tip that is specific to NFT...you should always control your environment to the best of your ability. It's important in NFT systems in particular because your roots are more exposed than other methods. This makes controlling air temp, humidity, and air flow even more important.
Control your temperature. Again, this is a tip that applies to many systems, but it's worth repeating. Your nutrient solution should always remain in the 65-68° range for root health, as well as optimal nutrient absorption and dissolved oxygen (DO) levels.
Decide how to start your plants. How you start your plants determines their future success in your NFT system. It's common to start in rockwool cubes, but I personally prefer to use Rapid Rooter starter plugs (I'm not a big fan of rockwool). However you decide to start seeds, make sure it will transplant well into NFT channels.
Keep your nutrient solution calibrated. You'll find your plants thriving in your NFT system compared to other methods, and doubly so compared to soil. But that increased growth means increased water and nutrient uptake. Make sure your plants are using water and nutrients at the same rate. If they're not, top up one or the other (or both) appropriately.
Monitor your pH. For most plants grown hydroponically, a pH range of 5.8-6.3 is ideal. It's very easy for large fluctuations to happen if you're not careful, so monitor often and make sure you're within this range, lest you face nutrient lockout. You can either do this with a pH test kit or something like the Bluelab pH Pen.
Remember to change your reservoir. About every week it's a good idea to change out your reservoir completely. The larger your tank, the longer you can go without a complete nutrient solution change, but it's better to change more often than wait too long. This ensures a perfectly calibrated system with the right amount of nutrition for your growing plants.
Keep light out of your reservoir. Make your life easier by keeping your roots in the dark. If light gets through and hits the roots and nutrient solution, you are opening yourself up to algae growth, which is both a pain to deal with and affects the growth rate of your plants.
Keep your environment clean. This is a no-brainer. Everything around your nft system should be as clean as the system itself. When you harvest from the system, give it a deep cleaning before you transplant new seedlings in.
Start slow. After you transplants your seedlings into your system, don't go too strong with your nutrient solution. The back of the bottle on most nutrients you can buy is higher than your seedlings need, so cut it by 25-50%, gradually moving up as your plants develop.
Use a half strength nutrient solution to start your plants off, moving to two thirds to full dosage rate (as detailed on the bottle) after the first nutrient solution change (about 7 - 10 days after planting).
Check your root health. Peek into your NFT channels once in a while to monitor your root health. They should be bright white and flourishing.
Use the right growing medium. Whatever you use to surround your plants' stems, make sure it isn't blocking the root zone from developing. This will stunt growth!
Support your plants. As your plants develop, you may need to stake them, tie them, or use some sort of support as they begin to fruit or flower.
Don't plant too dense. Because the roots grow through your NFT channels, you run the risk of clogging your channels if you plant too close together.
Transplant into your NFT system at the right time. Make sure that you transplant your plants into your system when the roots have developed to the point where they're already peeking out of the starter plug (or whatever else you used to start seeds). By waiting until this point, you're allowing the roots to have immediate access to water and nutrients once they're in the system.
Header image courtesy of Jackie