Nutrient Film Technique (NFT)

Marijuana Horticulture

by Jorge Cervantes

Nutrient Film Technique (NFT) hydroponic systems are high performance gardens that perform well when fine tuned. This relatively new form of hydroponics supplies aerated nutrient solution to roots located in gullies. Seedlings or cuttings with a strong root system are placed on capillary matting located on the bottom in a covered channel. The capillary matting stabilizes nutrient solution flow and holds roots in place. Constantly aerated nutrient solution flows down the channel, or gully, over and around the rots, and back to the reservoir. Irrigation is most often constant, 24 hours a day. Rots receive plenty of oxygen and are able to absorb a maximum of nutrient solution. Proper gully incline, volume, and flow of nutrient solution are key elements in NFT gardens.

Gullies or channels are covered to keep humidity high in the root zone and light from shining on roots. Root hairs responsible for most water and nutrient uptake cover the growing tips of advancing roots. These roots are submerge in turbulently flowing nutrient solution and the tops are intermittently in humid air. The nutrient solution is constantly aerated as it flows down the inclined gulley. the slope of the gulley is adequate to prevent water from stagnating. Often a filter is necessary to prevent debris from blocking gullies and pump.

Although high performance, NFT systems offer practically no buffering ability. In the absence of a growing medium, roots must be kept perfectly moist by the nutrient solution at all times. If a pump fails, roots dry and die. If the system dries out for a day or longer, small feeder roots will die and grave consequences will result. The system is very easy t clean and lay out after each crop. Only growers with several years of experience should try an NFT system if working alone. With help, they are easier to master.

Double reinforced bottom makes gullies durable and rigid when supporting large plants, root systems, and large volumes of nutrient solution. Some NFT gullies have ribs below to provide support and prevent warping and movements. The ribs also function as drainage channels and direct nutrient solution evenly along the bottom of the gully.

Many NFT systems are hybrids. For example, the nutrient solution in some hybrid NFT systems is delivered via spaghetti tubing to each plant. More irrigation sites help each plant receive proper irrigation. The nutrient solution flows through a small basket of growing medium before it runs down the gulley, over the roots, and back to the reservoir. Yet another NFT system employs spray nozzles inside the gulley. The nozzles spray nutrient solution on and around roots to keep the root zone environment at 100 percent humidity. The nutrient solution flows down a PVC pipe, over roots, and back to the reservoir.

Too often, these hybrid systems are poorly planned and designed. Many times they are constructed from white four inch PVC pipe. The thin white walls of the PVC pipe allow enough light to illuminate roots that they turn green or rot more easily. I have also seen systems with nozzles inside the PVC pipe. If a nozzle plugged inside a pipe, there was no easy way to access the nozzle for maintenance.

Nutrient solution is pumped from the reservoir into gullies via a manifold and tubing at the upper end. The table is setup on an incline so the nutrient solution flows quickly over roots t create an environment packed with air and available nutrients. A catchment drain directs the nutrients back into the nutrient reservoir.