How nutrient film technique grows lettuce

In nutrient film technique, lettuce sits in holes along gently sloped channels. A pump lifts nutrient solution from a reservoir to the high end, and it trickles down as a film only a few millimeters deep, so roots touch water below and air above, then drains back to the reservoir to be used again.

Controls

Labels

Animation speed

Flow per channel

Channel slope

Channel length

The model draws a short section; the math uses this length.

Step through it

ReservoirA tank holds water with dissolved fertilizer. Everything the plants need, other than light and air, starts here.
Pump and manifoldA small pump lifts the solution to a manifold at the high end, which feeds each channel through its own small outlet.
The filmThe channels tilt just enough for water to slide down as a thin sheet. Roots spread across the bottom and breathe the air above the film.
Too flatDrop the slope below about 2 percent and the film gets deeper and slower, so water can pool around the roots.
Back to the tankA gutter collects what the roots did not use and returns it to the reservoir, so the same water circulates all day.

How thick is the film?

For a thin sheet of water sliding down a wide, smooth slope, classic laminar film theory gives the depth: h = (3 x viscosity x q / (density x g x sin of the slope angle)) raised to the one third power, where q is the flow per meter of channel width.

This model assumes a 10 cm wide channel, water at room temperature, and no roots in the way, so treat the depth as a teaching estimate. Real root mats thicken the film and slow it down.

Try it: set the slope to 0.5 percent and the flow to 2.5 L/min. The film nearly triples in depth and the water takes much longer to reach the far end. Then raise the slope to 3 percent and watch it thin out again.

Why growers keep channels short

As solution travels down a channel, the plants pull out oxygen and nutrients. Very long runs leave the last plants with tired water, which is why many systems keep channels to about 12 meters or feed long runs from the middle as well.

Where Avid uses this

Water efficiency is a core goal of Avid's VerdantaIQ precision agriculture AI, which showed a documented 58 percent water reduction in a session co-presented at IBM TechXchange 2026.

Sources

Hydro hints: Nutrient film technique (EM 9457)Oregon State University Extension
Advancements and future perspectives in nutrient film technique hydroponic system: a comprehensive review and bibliometric analysisFrontiers in Plant Science, via PubMed Central

How to cite this model

Avid Solutions International. (2026, November 11). How nutrient film technique grows lettuce [Interactive 3D model]. Avid Field Lab. https://avidsolutionsintl.com/explore/nft-hydroponics

Last updated November 11, 2026

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