The Nutrient Film Technique

For devotees of hydroponic gardening, nutrient film technique promises to deliver a significant improvement.

| November/December 1979

Hydroponic gardening is nothing new to most of MOTHER EARTH NEWS' readers because the traditional methods of growing plants without soil were all discussed in "Hydroponics Mini-Manual."

Hand watering, wick growing, and periodic flooding with nutrients (using a pump and timer)—all methods which have their advantages and disadvantages—were described in that story. But now there's a new way to grow plants in liquid culture that offers some significant improvements upon the traditional procedures: It's the Nutrient Film Technique, or NFT (Sometimes also referred to as nutrient flow technique).

Based on research begun by England's Dr. A. J. Cooper in 1972, NFT is a system that uses a "film" of nutrient solution which flows continuously over the bottom of the channel containing the plants. The fertile fluid is constantly recirculated, and can be used (with periodic enrichment) for several weeks.

American researchers at the Long Island Horticultural Research Laboratory of Cornell University have been working with NFT since 1975, and they claim the technique's versatility is enormous! For example, unlike other forms of hydroponics, NFT can be used with or without a growing medium (the latter method eliminates the otherwise necessary beds of heavy—and hard to sterilize—gravel), it can be set up with either horizontal or vertical growing beds, it's practical both indoors and out, and it's economical to use and basic in design.

An NFT system is a snap to assemble, too. All that's needed are [1] a growing bed of some sort; [2] two containers (Plastic wastebaskets or dishpans are perfect for this job. Avoid unlined metal containers. The first supplies the nutrient—by gravity feed—to the growing bed, and the second acts as a receiving basin to collect the fluid after it has trickled past the roots); and [3] a pump, connecting pipes or tubing, and some screw clips to be used as control valves.

The fertilizer solution is contained in the elevated nutrient tank, from which it travels by way of a plastic or rubber hose to the growing bed. The rate of nutrient flow is easily controlled by a screw clip on the tubing. The liquid passes through the growing bed (which is at a minimum 2 or 3% tilt) and then drains into the receiving (or catchment) tank, picking up oxygen as it spills into the receptacle. The fluid completes the cycle when a pump in the lower tank—cued by the tripping of a float switch in the upper container—kicks in and sends the nutrient on its way upward.

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