Hydroponics is a method of growing plants without soil, relying instead on a water-based solution that delivers dissolved mineral nutrients directly to the roots. This cultivation technique provides growers with precise control over nourishment, leading to faster growth and efficient resource use. This article explores the Nutrient Film Technique (NFT), one of the most popular and commercially adopted hydroponic systems for producing leafy greens and herbs. We will detail its fundamental principles, necessary equipment, and specific operational requirements.
Defining Nutrient Film Technique
The Nutrient Film Technique is defined by delivering a shallow stream of water and nutrients to the plants’ roots. Plants are placed in channels or gullies designed for a continuous, recirculating flow of solution. The system’s name comes from the extremely thin layer, or “film,” of nutrient solution that flows over the roots, ensuring they are not fully submerged.
Maintaining this shallow flow accomplishes a simultaneous supply of water, nutrients, and oxygen to the root zone. The portion of the root resting above the thin film remains exposed to the air, accessing atmospheric oxygen. This constant air exposure prevents the roots from becoming waterlogged, which can lead to root rot. The design balances the uptake of water and minerals with the aeration required for healthy root respiration.
NFT was pioneered in the 1960s and provides plants with unlimited access to water while avoiding the conflict between water and oxygen availability common in older systems. Since the plants are not anchored in any growing medium, the root zone remains simple and clean. This technique is well-suited for fast-growing, shallow-rooted crops like lettuce, spinach, and culinary herbs, resulting in a high-yield system.
Essential System Components
Building an NFT system requires specific hardware components that create the recirculating flow. The foundation is the reservoir, a container that holds the nutrient solution (water and dissolved minerals). A submersible pump placed within the reservoir moves the solution through the system.
The nutrient-rich water is pushed through a delivery line to the highest point of the growing area. The growing channels or gullies, typically food-grade plastic, support the plants, which are often held in net cups with minimal media like rockwool cubes.
The return line or collection channel is positioned at the lower end of the growing channels. This system gathers the solution after it has passed over the plant roots, allowing it to flow back into the reservoir via gravity, completing the cycle.
How the NFT System Operates
The NFT system operates as a closed loop, minimizing waste of water and nutrients. The cycle begins when the pump draws the prepared nutrient solution out of the reservoir and delivers it to the elevated end of the growing channels.
The channels are installed with a precise slope, allowing gravity to pull the solution down their length in a thin, continuous film. As the solution flows past the roots, the plants absorb the necessary water and dissolved minerals for growth. The shallow depth of the film allows a portion of the root mass to remain exposed to oxygen, promoting efficient gas exchange.
Once the solution reaches the lower end of the channel, it exits through a drainage point and is guided back to the reservoir via the return line. This constant movement ensures the roots receive a steady supply of nutrition and helps introduce oxygen into the water, supporting root health.
Practical Considerations for Setup
Precise physical setup and careful management of the nutrient solution are required for a functional NFT system. The slope, or gradient, of the growing channels is a primary design parameter, ensuring proper flow without pooling. A recommended slope is typically between 1:30 and 1:40, meaning the channel drops one unit of height for every 30 to 40 units of length.
This gentle inclination ensures the solution flows smoothly and shallowly, maintaining the thin film. The flow rate is equally important, determining the speed and depth of the film. A guideline is to aim for a flow rate of about 1 to 2 liters per minute (L/min) for each channel to prevent the roots from drying out or becoming saturated.
Continuous monitoring of the nutrient solution is required for plant health. Growers must regularly check the pH level, ideally maintained between 5.5 and 6.2 for most crops to ensure optimal nutrient uptake. The electrical conductivity (EC), which measures the concentration of dissolved mineral salts, also needs frequent adjustment to match the plant’s specific nutritional needs.