The nutrient film technique, or NFT, is an effective but relatively simple hydroponic growing setup designed to give your plants all the essential nutrients they need using a recirculating system.
NFT systems are popular because they're modular, easy to build and expand, let you increase crop yield without too much extra effort, and require minimal maintenance. So you get a high yield compared to the effort you put in.
What Is The Nutrient Film Technique?
NFT is a type of active hydroponic gardening system, meaning it has moving parts. In this case, a pump recirculates a thin stream – or film – of nutrient solution along a system of shallow channels. The plant roots sit so they can readily access the nutrients needed to grow while still having access to oxygen so they don't suffocate.
Benefits of Nutrient Film Technique
An NFT system has many benefits for hydroponics.
- Great for water conservation. Because the channels are shallow, you only need a small amount of water.
- Minimal growth medium required. You'll grow in a net or open cup system, so you won't need vast amounts of growing medium.
- Easy to access plants. Easy access to the roots and the rest of the plant lets you check plant health and get on top of problems immediately.
- Easy to set up. An NFT system requires minimal equipment and few DIY skills.
- Scalable. Because this type of hydroponic setup is modular, it's straightforward to scale up.
- Eco-friendly. NFT systems are sustainable and have a low environmental impact because they reduce soil and water use. Organic nutrient solutions make it even more environmentally friendly, and you get organic produce.
Drawbacks of an NFT System
Although I'm a big fan of NFT setups, they have a few challenges you need to be aware of.
- It's an active system. Water and nutrients need to circulate constantly, so this hydroponic system uses power regularly.
- Potential for breakdowns. Because pumps and filters are involved, mechanical or electrical issues can quickly cause significant problems. You'll need to keep on top of maintenance and be ready to take action if you notice any changes.
- Root blockages. Large and vigorous roots can block the channels and drains.
- Larger plants require adequate support. Bigger plants, and those with heavy fruits, will need support structures to hold them up.
- Not suitable for root crops. Any plants, like carrots, parsnips, or leeks, and tubers like potatoes, don't work with nutrient film systems because there's no room in the shallow channels for the plants to grow.
How Does Nutrient Film Technique Work?
This type of hydroponic setup is a closed, active system. Plants with some growth media sit in net cups placed in grow trays or growing tubes, with the channels for the nutrient solution built-in, so the tips of the plant roots can dip into the water without drowning or developing root rot from lack of oxygen.
The grow trays are angled so gravity helps the nutrient solution return to the reservoir via the nutrient return drain. A reservoir tank below the grow trays contains water and the nutrient solution. Outside the tank is an air pump connected via air tubing to an airstone inside the reservoir to oxygenate the water. The reservoir tank also contains the water pump that pushes the nutrient solution up into the grow trays.
So, the nutrient solution starts in the reservoir, where it's pushed into the channels in the grow tray. From there, it flows through the channels, past the plant roots, and through the nutrient return drain back into the reservoir where it picks up oxygen from the air stone and begins the cycle again.
What Plants Are Safe To Grow With The Nutrient Film Technique?
Anything that doesn't have a tap root or tubers can work with a nutrient film setup. But lightweight plants and those with shallow root systems do best. Leafy greens, lettuce, and oriental vegetables like bok choi are the easiest to use with a continuous flow and shallow stream of nutrients because they don't need any support. Growing spinach, basil, and other leafy vegetables and herbs is the easiest way to start with this hydroponic technique.
You can grow fruiting plants, climbers, and heavy plants. They thrive with a moving film of nutrient solution. But they pose more of a challenge. Lower-growing options work well. You can grow strawberries, for example, as hydroponic plants, with nutrient film technique systems, and they don't need much support, as the fruit tends to dangle over the sides of the grow trays and hold the plant and its roots steady in the nutrient solution.
Larger fruit-bearing plants are more labor-intensive at times. Growing peppers, for example, requires you to provide a sturdy support structure so the pepper plants can grow to their full potential and provide plenty of fruit without falling over and the roots lifting out of the nutrient solution. It's easy to set up adequate support, but it can take some time if you're growing many plants. And it's an important part of the process.
Does The Nutrient Film Technique Need a Lot of Maintenance?
This hydroponic technique requires a small amount of maintenance. However, it is an active continuous flow system with two pumps, so it requires regular cleaning and care to ensure everything is in good condition.
As with all submersible water pumps, you must check yours regularly to look for mineral deposits. Ensure the housing and all the parts you can easily access are in good working order, and replace any showing signs of excessive wear to prevent a complete breakdown. Crops can experience significant damage in just a few hours if the system fails.
Check and clean out the drain, too, as roots and tiny bits of debris can get stuck in there and block the return.
It's also good practice to refresh the nutrient reservoir every 7 to 10 days to maintain quality and optimal nutrient levels.
And pay attention to deep cleaning between crops. When you harvest one crop, it's time to give the system a deep clean to prevent infection and algae growth. If you've seen no sign of infection, thoroughly scrub the tanks and grow trays with hot, soapy water. I like Dr. Bronner's castile soap because it won't kill the new plants, even if I accidentally leave a little residue. Also, take the opportunity to clean and tune up your pumps and flush the tubing.
How To Set up a Nutrient Film Technique System
Any hydroponic growers can tackle an NFT system, even beginner growers. Yes, you can get fancy kits that give you an instant setup, but you can also build your own.
You need a large, sturdy reservoir made of a garden-safe material. Remember, you'll eventually eat the plants you're growing, so you don't want nasties leaching in. I like a big glass fish tank. But it's a good idea to cover or paint the outside and cover the top to discourage algae growth and limit the chance of debris or contamination.
You can purchase grow trays or make your own from PVC pipes by cutting holes equally spaced along the length. You'll also need racks to hold the pipes. You can use a single length of pipe, run them side-by-side, or use them for vertical farming.
Remember to angle the pipes slightly so gravity helps the film of the nutrient solution go back to the drain and into the reservoir to recirculate.
You'll need to cut a small hole in the bottom of the last pipe in the chain to install the drain pipe.
Air Pump and Stone
You'll need an air pump on the outside of your reservoir connected to an airstone inside the tank to boost the oxygen level of the nutrient solution.
A single air stone disc will suffice in a small setup, but you'll need an interconnected array for larger-scale operations to provide sufficient nutrient oxygenation.
Anywhere water flows through a tube, that tube should be opaque. Pale and transparent tubing encourages algal growth, which you don't want, as algae compete with the plants for oxygen uptake. Plus, some types of algae are dangerous to humans and animals.
Your submersible water pump needs enough power to move the nutrient liquid around the system. Remember, if you're moving water vertically or have a large, many-layered setup, you'll need a reasonably heavy-duty pump. For a little 25-gallon reservoir, you can get away with a 250 gallons-per-hour pump.
Net pots are either webbed mesh pots or little plastic pots with slits or webbing all around the sides. They hold the growth medium, secure the plants, and let the roots grow to reach the nutrient solution.
Make sure you choose ones that fit into the holes in your pipes without falling through.
As we've already established, with an NFT system, plants can access a constant flow of nutrients. The best-growing media for NFTs is one with low water holding capacity or WHC. Instead, the primary use of growing media in these hydroponic systems is for plant support rather than water or nutrient retention. So go for something with a low WHC, like clay pebbles.
Choosing the right hydroponic nutrients is critical. I only practice organic gardening, so I use a reputable organic nutrient product so I know there are no unwanted chemicals in my system. Whichever one you choose, it must be high-quality, well-balanced, affordable, and easy to use.
As nutrient requirements vary throughout the lifecycle of the plant, you may also need to choose different nutrient concentrates for different growing stages.