The Nutrient Film Technique (NFT) is a popular, soil-less method of growing plants in hydroponics. Developed in the 1960s by Dr. Allen Cooper, it is now widely adopted in commercial agriculture due to its efficiency. NFT involves a continuous, recirculating stream of water that delivers necessary nutrients directly to the plant roots. This active system provides a highly controlled environment, making it a sustainable alternative to traditional farming methods.
Core Mechanics of Nutrient Film
The defining characteristic of an NFT system is the shallow, thin stream of nutrient solution, or “film,” that flows across the bottom of the growing channels. This film is consistently circulated, ensuring the roots receive a steady supply of water and dissolved minerals. The flow is maintained by gravity, requiring the growing channels to be positioned on a slight incline.
A proper slope is necessary to ensure the solution moves without pooling or rushing past the roots too quickly. The ideal range is often cited between 1:30 and 1:40, or a 2% to 3% drop. This flow rate is typically maintained around 1 liter per minute per channel to prevent nutritional deficiencies or excess water accumulation.
The thinness of the nutrient film is crucial because it allows the root mass to be only partially submerged in the solution. The upper portion of the roots remains exposed to the air within the channel, which facilitates optimal gas exchange and provides oxygen directly to the root zone. This dual exposure to nutrient-rich solution and air promotes rapid and healthy plant growth.
Essential System Components
An NFT setup is a closed-loop, recirculating system composed of several hardware elements. The foundation is the nutrient reservoir, a container that stores water mixed with the necessary plant nutrients. A submersible pump, often connected to a timer, pushes the nutrient solution up to the highest point of the system.
The solution then travels through delivery lines to the growing channels, also called gullies or troughs, where the plants are situated. These channels must be made from food-grade, opaque materials to prevent light penetration and the growth of algae. After flowing over the plant roots, the solution collects in return drains and uses gravity to flow back into the reservoir for recirculation. Monitoring equipment, such as pH and electrical conductivity (EC) meters, is used to regularly test and adjust the solution’s composition to maintain optimal nutrient levels.
NFT Compared to Other Hydroponic Methods
The Nutrient Film Technique is distinct from systems like Deep Water Culture (DWC) and media-based drip systems because it uses no solid growing medium, or substrate, to support the plants. Plants in NFT are typically held in net cups, with their roots dangling into the channels, unlike media-based systems that rely on materials like rockwool or coco coir. This lack of media simplifies sanitation and reduces the risk of soil-borne diseases.
NFT handles root zone oxygenation differently than DWC. In DWC, plant roots are fully submerged in a large volume of nutrient solution, requiring an air pump and air stone to actively bubble oxygen into the water to prevent root rot. NFT achieves aeration passively, as the roots are only partially coated in the nutrient film, leaving the root mass exposed to the oxygen-rich air inside the channel.
While drip systems are often used for larger, fruiting plants, NFT channels are typically shallower and shorter, limited to a maximum length of 10 to 15 meters to prevent nutrient depletion at the far end. NFT systems are highly vulnerable to power outages; if the pump stops, the thin film of water quickly disappears, and the exposed roots can dry out rapidly. The larger water volume in a DWC system provides a greater buffer against temporary system failure or temperature fluctuations compared to NFT’s low-volume film.
Suitable Crops and Applications
The NFT system is best suited for growing plants that are lightweight, have quick growth cycles, and possess shallow root systems. Leafy green vegetables, such as lettuce, spinach, and kale, are the most common and successful crops due to their ideal characteristics. Many culinary herbs, including basil, mint, cilantro, and parsley, also thrive because their smaller root masses do not easily clog the narrow channels.
The system is successfully used for cultivating strawberries, which are lightweight and do not require the structural support of a solid medium. NFT is not recommended for large, heavy, or deep-rooted plants, such as tomatoes, squash, or root vegetables like potatoes, as the system lacks the necessary physical support. The extensive root systems of these larger crops can quickly block the flow within the channels, leading to water stagnation and system failure.