The Nutrient Film Technique Explained

Ed Wike
Written by
Last update:

How NFT Systems Work

Using the NFT hydroponic system, plants are completely separated from the growing medium and placed in a special flow cell. Water is continuously moved through the cell by a submersible pump. It flows over the frame containing the plant roots, and the roots are exposed to a thin film of nutrient solution that falls from the casing above.

The continuous drip from the plant tray above the growth media results in a constant moist environment and encourages very even plant growth. The water that drains from the growth media is captured in the bottom sump and recirculated back into the system.

Using NFT hydroponic systems, you can grow one plant per cell or grow several plants in a cell. The size of the cells should match the size of the plants, those of you growing in a space, or have limited grow space will want to work with smaller plants. The system is very good for plants that need fragile or staked support. Usually, NFT hydroponic systems are used with leafy greens like lettuce and kale, although any plant that can be grown in soil can be grown with NFT hydroponic systems.

Benefits of NFT

  • Plenty of oxygen [[fertilized]] water containing nutrients flows through the film.
  • Light is transmitted through the upper level of water, and algae can grow in this light.
  • Algae growth in adequate amounts improves the tilt of the algae to oxygen.
  • The floating lettuce-like plants are oxygenated, while growing in the sun, in a soilless environment.
  • When the plants are used as a protective cover for fish fry.

NFT, as a technique, limits the space where bacteria and other microbes can grow by making sure there is no excessive film formation on the surface of the water. It completely avoids any oxygen deficiency that may occur in other types of hydroponic systems.

Fertilizers in the wastewater can be managed by the NFT technique. The primary advantage of NFT is the easy management of nutrients because the nutrient levels remain reasonably stable.

Downsides of NFT

The NFT system attracts a lot of attention and many commercial greenhouses use it to grow vegetables. There is, however, one big problem withthe Nutrient Film Technique. Since no pump or any other equipment is used, it saves substantial amounts of energy.

The downside of the system is that it can take a lot of time before vegetables reach marketable sizes. They are in competition with other hydroponic products, and it takes a lot of time before they can be sold.

How to Build a NFT System

In recent years, aquaponics has been gaining popularity due to its low cost and the ability to grow many types of plants and fish. Growing plants and fish together offers a number of benefits, and the method is referred to as symbiotic because the fish provide natural fertilizer for the plants.

Even though fish are larger than plants and would therefore appear to take more water than they can produce, they don’t actually use the tank water directly. The fish waste first becomes ammonia which is naturally converted into nitrates by the nitrifying bacteria. The plants then use the nitrates to fuel their growth.

Aquaculture systems take advantage of the relationship between plants and fish by placing plants in a basin designed to support the fish tank. Instead of a typical aquarium, the basin is filled with clay pellets that hold the water for the plant root systems but have holes for excess water to drain into the tank from the roots. This system offers a few advantages over using a traditional aquarium/plant combination. The most obvious advantage is that there’s no risk of fish jumping out of their tank. The water is also filtered by the clay pellets themselves, saving both waste water and energy.

The Reservoir

The nutrient film technique (NFT) is a hydroponic system that mimics the conditions of an aquatic ecosystem. It is suitable for a wide range of crops and produces consistent results.

Here’s how it works: the nutrient film technique makes use of the natural groundwater that percolates through the planting area. The reservoirs are usually made of plastic or wood and are filled with a diluted nutrient solution. The crops are placed in the planting channels, elevated slightly above the reservoir, and leaves and roots dangle into the nutrient solution. The nutrients are absorbed by the plant roots and transferred to the leaves and fruits. The nutrients are then released into the surrounding water, feeding both crops and beneficial microorganisms.

The NFT system is advantageous for several reasons. One of the most important attributes is that plants grown in an NFT system have a higher yield, compared to competing growing technologies. There’s also a smaller risk of contamination. This means you need less pesticides than with other methods, such as outdoor hydroponics. The secret is the shallow solution (0.75–1.5 inches/2–4 cm), which also helps reduce the risk of root damage.

NFT Channels

To explain one of the most nutrient manipulation techniques, we will look at an inter-connected network of continuous channels. This is the basic idea of the technique but there is of course variation to occur. The channels shape themselves around the crop depending on the layout of the gut. This kind of manipulation allows an immense amount of control, which has to be accounted for if the method is not extremely tight. For instance, if the channels are not correctly shaped around the crop, the distance between the roots of the crops will be less than desired. The roots could take up a different spot or some crops may take up less than desired space than others.

There have been numerous experiments and simulations that have proven that above ground plant support systems can be used for intensive cropping systems as well. The idea of the support system is to minimize the exposed surface area. Since the crops are grown in a highly concentrated area, the amount of nutrients that are needed will be as well. But to make sure that enough nutrients make it to the roots, a support system is needed to protect the crops. By growing on a support system, there is a large amount of sugar transfer that occurs. This is because there is less competition for nutrients between the plant’s roots and the plants on top, are also only a few inches away.

Air Pump

The air pump is used to create air bubbles that the plants use for oxygen. The air pump is similar to a filter on an aquarium, but you can also add carbon or bacteria to it to remove bad odors or add to the aquarium water to help remove harmful chemicals. Hang the air pump about 10 inches above the aquarium water.

The air stones attach to the air pump and then bubble the air up through the aquarium. Use a hole punch to make a whole in the foam or a plastic lid at the level where the aquarium water will match the water level in the tank. The air stones can be hooked up with air hoses and the air pumps can be run by electricity or by batteries.

Water Pump

The water pump is used to create the water flow that will move the air bubbles up and down through the aquarium. Use a plastic tub with a section cut out to allow the pump to sit inside with water circulating around the pump, creating the water flow through the aquarium. The aquarium arms with air stones will direct the flow of the water. Some people prefer to add a few plastic plants to the tub to help direct the water flow and add color to the aquarium.

Air Stone(s)

The other area in which the NFT systems is superior to other systems is the amount of surface area of plant roots that it provides. I’ve said it before and will say it again, the most important requirement for plant growth is access to a large surface area of water (so roots can access oxygen), which the plants get with the hydroponics systems. This photosynthetic (plant) uptake of oxygen produced via nanotechnology produces a greater volume of oxygen than required for the plants preventing bad odors. But that also means that the roots have a great abundance of oxygen at the root surface area. Within the Root Zone of the Veg Plot there are several types of materials such as gravel, rockwool, foam, etc. Each of these materials provides a different surface profile, which allows for greater surface area for plant roots to grow into.

Airline Tubing

The long lines of plastic tubing sticking out of your aquarium are no mystery. They are air stones and powerhead tubing and are used to help maintain good water circulation, but why are they so long? Airline tubing is meant to handle large volumes of air despite the resistance of the fluid, and it has to be strong enough to stretch across your tank, which can be ten feet. The proper size tube is important for the health of your fish. Using one that is too small or thin and you end up with a siphoning effect that pulls water out of your tank. Using one that is too bulky or fat and the bubbles won't rise to the surface.

Select the correct size for you aquarium. If your tank measures 10' long, choose 1/2" airline tubing. If your tank is 18" deep choose 3/8" airline tubing.

Standard airline tubing: You will also see basic airline tubing sold in less specialized pet products stores for use with aquarium air pumps. These are a little thicker and sturdier than the airline tubing that might have come with your air pump. They don't work as well, but if you are in a pinch and need some tubing, they'll do fine.

Tygon Plastic: Your aquarium air pump tubing should be made of food-grade Tygon. This plastic is as soft as silicone but isn't porous and doesn't harbor bacteria. It is commonly used for plastic tubes in the brewing industry.

Water Pump

Requirements The nutrient film technique is a system of hydroponic growing in which plants are grown in a layer of continuously flowing shallow water that contains all of the nutrients that the plant needs. A continuous stream of water is pumped past the rooting zone of the plants.

This method of growing is used for the production of high quality herbs, salad greens, vegetables, flowers, and potpourri.

The nutrient film technique works best in greenhouses where the temperature and the humidity can be manipulated and controlled.

It can also be used in grow boxes or hydroponic systems that are constructed in a space outside of a greenhouse.

The plants are grown in various recycled materials including plastic kiddie pools, garbage cans with holes drilled in the bottom, large aquariums, and plastic-lined wooden boxes.

The material that the plants are growing in allows the water to flow freely, but doesn’t let the plant roots come in contact with the water. The flowing water oxygenates the nutrient solution and the plants[2]

The plants can be spaced closely together in the grow box, and the grower can have several such boxes in production at one time.

It is most important that the grower examines the water film daily for blockages and nutrient salt buildup. The water pump should run on a timer, and the pump should be on for about 10 seconds every 30 seconds, or at least every minute.

Growing Tips For Your Nutrient Film Technique System

The NFT gardening system, like any hydroponic method requires good growing medium, nutrients, and a pump to run the system. A reservoir and a flood gate are usually the only other parts required. The NFT system requires much less equipment than the DWC or Dewy Cup systems, and can produce high quality harvests in a small footprint.

The main difference between the NFT system and other hydroponic gardening systems is the way the plants are watered. Most other systems require the plant's roots to be periodically bathed in a nutrient solution. The NFT system uses a continuous, self-contained flow of graduated concentrations of nutrient solution and air to deliver the right balance of nutrients and water for the plants.

Higher up the plants root area than most hydroponic systems, the plant gets water with dissolved oxygen, but it also gets fresh air as the nutrient solution is recycled through the plant. This extra oxygen allows the roots to get a great supply of oxygen. In enclosed systems like the DWC or the Dutch bucket systems, the roots have no exposed surfaces to get oxygen from, so the roots can be damaged without the plant showing any obvious symptoms of distress.