Related guides: system setup checklist · root-zone guide
Nutrient film technique (NFT) sends a shallow stream of nutrient solution through sloped channels so roots can access both moving water and air.
How NFT delivers water
A reservoir pump lifts solution to the high end of a channel. The solution flows along the bottom and returns to the reservoir. Net pots hold plants above the film while roots grow into the channel. The film should wet roots without turning the channel into a deep flooded tube.
Flow depends on pump capacity, head height, tubing, fittings, channel slope, and the number of channels. A system that works on a bench can behave differently after tubing is routed or filters begin to clog. Test the return path with plain water before adding a crop.
For the next step, see the ebb-and-flow guide.
Why crop choice matters
Leafy greens and small herbs fit NFT well because their root systems and water demand are modest. Heavy fruiting crops need support and can produce roots that obstruct a narrow channel. Crowded channels also make it harder to inspect individual roots and remove a plant without disturbing its neighbors.
NFT uses relatively little solution in the channels, so a pump interruption can become urgent. Keep the reservoir accessible, inspect return flow, and make the system easy to observe. A visible mark on the reservoir can reveal water loss and pump behavior.
Failure points to inspect
- Uneven flow: compare the high and low ends of the channel before changing nutrient strength.
- Light leaks: cover gaps around net pots and translucent fittings to limit algae.
- Roots and sediment: check the pump intake, channel outlet, and return line between crops.
- Changing slope: support channels so their angle does not shift under plant or water weight.
- Low buffer volume: leave enough reservoir capacity to soften a short interruption.
If one plant looks stressed, compare its channel position, root space, and flow to neighboring plants. Use the system setup checklist before planting and the root-zone guide if roots smell or shed tissue.
Virginia Cooperative Extension; Cornell Controlled Environment Agriculture.
