Nutrient Film Technique (NFT) growing is primarily used for growing leafy green plants. Using this method a thin stream of water flows through a rectangular channel about 3" to 10" wide (wider channels are used for fodder crops). Because the nutrient stream forms a thin film in the bottom of the channel it gives the method its name. Plant roots are bathed in this stream of nutrients and grow very quickly.
CropKing offers channel with a slightly raised middle to help the film spread widely rather than concentrate plant roots into the middle of the channel. The CropKing channels have removable top caps to keep dirt from contaminating the nutrient film and to make it easier to clean the channels. These caps are punched with specially sized holes to enable a grower to precisely space crops for best growth. In addition, the covers prevent evaporation loses.
When installed the channels are sloped about one inch over every thirty-six to forty inches to allow the nutrient film to flow easily. The nutrient liquid is pumped in through a small diameter feed line, flows down the channel to be collected at the lower end. At the lower end the film flows back into the reservoir ready to be reused.
What Plants can be Grown in NFT Channels
NFT channels are primarily used to grow leafy green plants with a short growth period. Bibb and leaf type lettuce is an ideal plant for such a system but you can grow other leafy green plants such as spinach, broccoli Raab, and certain herbs. Larger plants such as cabbage, that take longer to grow, are heavier, and have larger root systems are not suitable for an NFT system.
Starting Seedlings for NFT Channels
Most hydroponic plants are started in cubes and transplanted into the channels. The cubes can be made of rockwool, coir, peat moss or a type of spun polymer that allow the nutrient film to soak the cube but also allow the film to flow past it.
To start seedlings the first step is to wet the cubes. Run several quarts of water through the cubes. This not only wets them but also cleans out any excess salts in the cubes. set the cubes in standard seedling flats before placing a seed in the dimple in the center of the cube.
You will find it difficult to set a single seed in the middle of each cube because the seeds are so small. For that reason many growers use pelletized seed even though it costs a little more. Seed about 10% more seeds than you will need to allow for wastage or poor germination. Water the cubes with warm water (70-75o or 21o to 23o C). Keep the seedlings damp and keep the temperature in the germinating area around 65 to 75o (18o to 23o C) Keep the temperature around the seedlings at least 55o (13o C) at night and up to 65o (18oC) during the day. Moisten the seedlings with either water (no nutrients) or half strength nutrient solution until the plant roots reach the bottom of the cube in about ten days to two weeks.
How to Plant Your NFT System
When you see roots at the bottom of the cube or when the seedling leaves are around 2" long, transplant into NFT channels and fertilize until the plants reach harvestable size. When placing cubes in the channels the slots in the bottom of the cube should run along the channel to help the nutrient film flow easily. Nutrient flow at this time should be about 8 to 10 ounces of solution per minute at a pH of 5 to 5.8 depending on temperature and time of year.
Harvesting Your Crop
To harvest the crop, the lettuce and its cube are gently lifted out of the channel. The cube can be disposed of by trimming the roots away, or it can be left in place depending on what your buyer prefers. You might also have to trim away any leaves with brown tips or discoloration. Immediately after harvesting the crop should be cooled, packed and shipped. Delays are critical to the quality of your product at this stage.
Cleaning Your NFT Channels
After each crop your NFT channels should be cleaned to prevent any pathogens moving on to your next crop. The CropKing NFT channels are relatively easy to clean in that the top caps can be lifted off exposing the channels for cleaning. To clean the channels you can make up a mixture of water with a half cup of bleach added to kill of organisms and then rinse with fresh water or you can clean with a bacterial fungicide such as Oxidate or Zerotol. By cleaning your channels regularly you will not transport bacteria or pathogens from one crop to the next.
If you are planning a small system, using concentrated solution is an option, but at CropKing we recommend using an easily dissolvable granular fertilizer called Hydro-Gro. Hydro-Gro recipes are based on the plant requirements only. However, if your water supply analysis tells us that your water already contains specific elements we can change the formulation to suit your water supply. Because some fertilizer materials react together in storage, CropKing supplies them in separate containers for the grower to mix in separate tanks. Only after the granular fertilizer is dissolved is it mixed together.
After mixing the nutrient solution is pumped to the upper ends of the channels allowing gravity to move it down toward the lower end. At the lower end the solution is funneled back intot he reservoir. In some systems the nutrient system flows continuously, while in others it is pumped through the system every three or four hours.