What Is NFT Hydroponics?
NFT, or nutrient film technique is a kind of recirculating hydroponic system.
The nutrient film technique gets its name from the very low-flow irrigation that feeds the plants in the system. Water is pumped into a flat channel slowly so that a thin “film” of nutrient solution is constantly present.
How Does NFT Work?
NFT is designed around that thin film of liquid running through the system.
When root systems touch the film, they can drink up the nutrients they need without sacrificing aeration. By balancing the right amount of water flow, nutrients, and oxygen in the system, impressive yields can be achieved with little effort.
Here’s how the system works…
A long flat channel, almost something like a rain gutter on your house, is set up at a slight angle.
Holes are drilled in the top of the channel to house net cups with seedlings in them.
A reservoir with a water pump sends nutrient solution up to the channel where it flows down pulled by gravity, contacting the plant’s roots along the way.
At the end of the channel, the water drains down into the same reservoir where it started.
This system is very similar to an ebb and flow system, except that with NFT the irrigation runs constantly and only a thin film of water is allowed to drip through the channel.
While many people put air stones and air pumps into their NFT systems, this isn’t necessary.
The whole point of NFT is to keep the bare minimum level of water flowing through the channel to leave plenty of room for the roots to absorb oxygen.
It’s the empty space inside the channel that makes the magic happen.
What I see many growers doing is flooding their NFT channel, which cuts off the plant’s oxygen supply. To remedy this, they add an air stone and air pump to the system to get that oxygen back.
NFT with an excessive water flow becomes a kind of modified ebb and flow system which misses the point of the nutrient film technique.
That being said, an air stone and air pump certainly won’t hurt your system, it’s just an unnecessary cost that can be avoided by simply tweaking the water flow.
And that is the tricky part of NFT—getting the channel length, channel slope, and flow rate correct. More on this below.
What Plants Grow Best In an NFT System?
As with most hydroponic systems, you can grow almost anything, but what you should grow is a different story. It all comes down to convenience and efficiency.
Most growers use NFT systems to grow leafy vegetables like lettuce, spinach, bok choy, kale, and herbs. These plants thrive under constant irrigation.
On the other side of the spectrum, certain fruiting plants like tomatoes, peppers, and cucumber plants do better with carefully limited water supplies.
Also, because no growing media is used, other than maybe a small chunk of rockwool, larger plants will lack support in an NFT system.
You won’t be able to grow a large tomato plant in a system like this without building in some kind of trellis or support to keep it propped up and supported.
How Do You Set Up an NFT Hydroponics System?
You can build an effective NFT system yourself at home. The materials to do this are affordable and the setup is simple.
You can tweak this system to your liking, using different materials or configurations.
What you will need:
- 4-inch PVC pipe
- 2 PVC end caps
- Plastic tote (5-gallon)
- 3-inch net cups
- Water pump
- ½-inch poly tubing
- Scrap wood (2×4)
How to Build an NFT Hydroponic System Step by Step
Step 1: Cut your 4-inch PVC pipe down to size. You can make this as short as you want or up to around 30 feet. This will be your channel.
Step 2: Drill a ½-inch hold into one of the end caps.
Step 3: Drill or cut a series of 3-inch holes in the top of your PVC pipe, about 8 inches apart. This is where your plants will go.
Step 4: Drill a ½-inch hole into the bottom of the PVC pipe, on the opposite side of the holes you just cut.
Step 5: Attach the end caps.
Step 6: Take your plastic tote and drill two ½-inch holes into the lid, one on the left and the other on the right. Place the water pump into the tote.
Step 7: Take your scrap 2×4 and cut two 6-inch sections. Cut a groove into each one, a simple “V” will do. These grooves are to hold your PVC pipe in place. Cut or sand down one of these pieces on the bottom to make it slightly shorter than the other.
Step 8: Now decide where you want your NFT channel to sit. You can place it directly on the plastic tote or on a table or bench nearby. Set up your two pieces of wood and place your PVC pipe on top so that it rests securely in the grooves.
Make sure the shorter piece of wood is on the drain end, so that water will run towards the drain.
Step 9: Cut a length of your ½-inch poly tubing long enough to connect the pump to the hole in the end cap. Stick one end of the tube into the end cap, and run the other end through one of the holes on the reservoir lid and attach it to the water pump.
Step 10: Cut a short length of ½-inch poly tubing to connect the small hole on the bottom of the PVC pipe to the other hole on the lid of your plastic tote.
Step 11: Place net cups with seedlings into the 3-inch holes in the PVC pipe.
Step 12: Add nutrient solution and turn on the pump.
NFT Tips for Channel Slope, Flow Rate, and Modifications
The roots of your seedlings should just barely touch the bottom of the channel.
Tweak the water flow of the pump so only a thin film of water runs through the bottom of the channel.
If you keep the water flow low and let it run constantly, you won’t need an air pump, air stone, timers, or any special equipment like that.
The slope of your NFT channel could be as low as 1:100 but most slopes run closer to 1:30 or 1:40. With the slope of an NFT system, the trick is to get a subtle decline but not allow any pooling to occur.
As long as a thin film of water is flowing through the channel and draining on the end, you are golden.
A quick note on flow rate—
When channels are longer than 40 feet, your plants may suffer from a lack of nutrients. The plants closer to the source of the nutrient solution will suck up nitrogen, depriving the plants on the end of the channel of this essential nutrient.
When this happens, the plants on the end of the channel won’t grow properly.
To prevent this, all you need to do is keep each channel less than 40 feet.
Alternatively, you can make channels as long as you want and just add irrigation lines from separate reservoirs into the channel every 20 feet or so.
If you have multiple irrigation lines in your channel, make sure you turn down the water flow of each of them. You don’t want twice as much water in your channel, you still just want a thin film.
AND, a note on air stones—
Some growers like to put an air stone into their NFT reservoir—this is unnecessary. The whole point of NFT is to keep the water levels low so the roots get plenty of oxygen but still contact enough solution to thrive.
If you need to add an airstone, you are probably running way too much water in your system, basically turning it into an ebb and flow system rather than a true NFT system.
NFT Pros & Cons
The nutrient film technique is so widely used for good reason, but it can’t do everything. There are a few limitations to be aware of.
- Very water efficient
- Mostly passive system
- Perfect for leafy vegetables
- Inexpensive to build
- Not ideal for fruit-bearing or large plants
- Recirculating systems run the risk of spreading diseases from plant to plant
- The system retains no moisture, so in the event of a power outage your plants may be damaged or killed from a lack of water
NFT Frequently Asked Questions
How Do You Start Plants For an NFT System?
You can start your seeds or use seedlings like you would in any other system.
Take a piece of rockwool (or a Rapid Rooter) soaked in water or a gentle nutrient solution and place your seed in it. Pop it into a tray and set it in the sun or under grow lights.
Once the seedling has developed a strong root system, just place it into a net cup and put it into your NFT system.
The only trick is to make sure that the roots will reach the thin film of nutrient solution on the bottom of the channel from the moment the seedling enters the system.
If the roots or rockwool don’t yet reach the nutrient solution, you can set your seedling to grow a while longer in a deep water culture, ebb and flow, or Kratky system to allow the roots to lengthen.
Alternatively, you can just put the seedling into your NFT channel and temporarily increase the water flow so the roots or rockwool touch the solution.
But, be sure to turn the water back down once the roots are long enough. You don’t want to run too much water in an NFT for very long or you will starve the plants of oxygen.
Are There Premade NFT Kits For Sale?
Yes, you can find fully-equipped premade NFT hydroponic kits online, like this one on Amazon.
These systems are great if you want to quickly jump into NFT hydroponics and don’t want to spend the time rigging together a DIY build.
However, buying a premade NFT system will cost you a bit more than building one yourself.
Can You Use an NFT System Indoors?
Yes, the only difference is that you will need to put your system somewhere with an ample amount of sunlight or use grow lights.
Because most of us don’t have that much natural lighting indoors, the best course of action is to invest in a quality fluorescent or LED light.
With grow lights, I always recommend going for a full-spectrum light that emits both blue and red light.
Blue light promotes chlorophyll production and foliar growth while red light encourages blooming.
While leafy greens can get by with just blue light, you will get the healthiest plants and have the most versatility with a full-spectrum bulb.
For an average-sized NFT system, I’d recommend a light like this one.
This is an affordable LED grow light that has enough power for your NFT and has better coverage than popular square-shaped grow lights.)
An LED light should be positioned 12 to 24 inches above your plants. Just make sure to give your plants plenty of headroom to grow!