Nutrient Film Technique (NFT) in Hydroponics: How Does It Work?

Nutrient Film Technique (NFT) in Hydroponics: How Does It Work?
External Guest Writer
June 6, 2022

What is the Nutrient Film Technique?

The Nutrient Film Technique is an irrigation system developed in the 1960s by Dr. Allen Cooper, an agricultural researcher at the Glasshouse Crops Research Institute. In this hydroponic setup, plants are grown in a soilless substrate, using a water pump to recirculate and deliver nutrients directly into plant roots in shallow channels to prevent root rot.

The Nutrient Film Technique is an active system, much like the Ebb and Flow system. Unlike the flow and drain system, however, this hydroponic system continuously flows water and nutrient solutions through the setup using a tray that creates a channel of water that flows through the system, irrigating plants.

When done correctly, the nutrient film technique promotes the growth of plants, leading to quicker harvest times that passive hydroponic systems cannot achieve. Plants get a steady stream of water, oxygen, and nutrient solution to grow lush and plentiful crops.

The Nutrient Film Technique Setup

A tray channel typically provides a very shallow nutrient-rich water to the plants to prevent overwatering, while still providing ample nutrient supply to the roots. Water pumps bring the solution from the water reservoir below to the tray channel, and excess nutrient solution then trickles back down into the reservoir for recirculating.

Nutrient Film Channels

The vast majority of commercial hydroponic growers make use of PVC pipes as channels for their growing medium. These pipes can measure anywhere from 3 meters to 20 meters and beyond, and have very shallow stream lines between 60 and 150 mm wide with an optimal film depth of 40mm, at a slope of 1.5%.

These systems are constantly flowing to provide much-needed nutrients and oxygen to plants at a rate of 1 liter per minute per channel. The large tap root systems take in the nutrients they need to grow properly without drowning in stagnant water reservoirs. As a result, plants are able to grow at a faster rate with leafy greens growing to harvesting size in a matter of weeks.

Aeration and Oxygenation

An air pump is used to help aerate the water, and maintain optimal pH and nutrient levels. Like the water pump, the air pump is actively working to sustain the plant roots in the system. The setup differs from the flood and drain mechanics of other hydroponic systems, making use of a nutrient solution recycling setup instead.

Nutrient Solution

The nutrients present in a hydroponics system is highly dependent on the crop grown in the setup. As different plants require different nutrients, it is essential to grow only plants of the same or similar varieties in order to deliver exactly the type and amount of nutrients each crop requires to grow bountiful harvests.

Lettuce, for one, requires nitrogen-rich solutions with balanced levels of potassium and phosphorus. Tomato and other plants in the nightshade family will require calcium and magnesium as well.

Growing Crops in Nutrient Film Technique Setups

The setup is perfectly suited to grow different varieties of lettuce: from iceberg lettuce to romaine lettuce, and even cabbage. However, some commercial farmers have found success in growing perennial plants such as strawberries.

Despite its advancements in growing a variety of crops, this type of hydroponic system is most commonly used for lettuce and similar leafy greens as the crops grow best with an unlimited supply of water packed with a nutrient solution. Lettuce also takes up less space, allowing growers to plant multiple heads at any given time.

Hydroponic growers often make use of rockwool blocks to store nutrients as a fail-safe in case of pump failure. This would allow crops such as lettuce and herbs to continue drawing nutrients stored in the rockwool despite irregularities or halts in the flow rate of the nutrient film channels.

The Sustainability of the Nutrient Film Technique

The Nutrient Film Technique system is recognized for its sustainability as it recycles nutrient solution throughout the setup, ensuring every essential substance is used in the hydroponic system. The used nutrient solution flows back into the system, creating a sustainable way of growing without wastage.

This system is also energy-efficient, low-cost, and requires relatively low maintenance to operate. Its sustainability, coupled with its space-saving and soilless features, makes the nutrient film technique popular among urban farmers and commercial growers.

This system was designed for plants that are most susceptible to root rot, like roses, strawberries, and grapes; thus, allowing farmers to grow these crops in hydroponic systems. These systems allow growers to plant and harvest crops that are notoriously difficult to grow in soil mediums and passive hydroponic systems.

Perceived Cons of the Nutrient Film Technique

Not all plants benefit from hydroponic systems. Because this type of hydroponic systems recycle the water through the setup, it can spread root-borne bacterial and fungal diseases from plant to plant. In fact, this is the very reason Dutch farmers rejected the nutrient film technique in hydroponics, in fear of wiping out their entire harvest through pathogens spreading via the nutrient solution.

Herbs are especially susceptible to root rot, therefore disinfection of plant roots is a must before placing the crops into this system. A properly designed system should have little problems with disease maintenance, optimizing the pH and oxygen levels of the water.

Despite disease maintenance and techniques, select commercial growers opt out of utilizing this system in hydroponics as the risks of disease spread is considerably high. Water temperature fluctuations and pump failures are additional perceived cons in maintaining a nutrient film setup.

Growing From the Roots Up

The nutrient film technique was created to keep supplying the demand for crops and herbs, while doing so in a sustainable method. The method has proven to be beneficial to plants, as the nutrients are absorbed directly through the roots.

For many growers, these systems provide a simpler way to grow sensitive plants, taking the guesswork out of gardening for harvest. As the hydroponic system continues to develop, no doubt more alternative systems will continue to pop up and provide solutions to make growing easier.