Nutrient Film Technique or NFT is a type of hydroponic system where a shallow stream of water containing all the essential dissolved nutrients required for plant’s growth is re-circulated past the bare roots of plants in a watertight gully, also known as channel. As the depth of the recirculating water is extremely shallow, a little more than a film of water, hence the name ‘nutrient film’. NFT uses a reservoir with a submersible pump that pumps up the water from nutrient reservoir which then moves to a clarifier, then to channels and finally drains back into the reservoir due to gravitational force.
A well designed NFT system should have the right channel slope, the correct flow rate and precise channel length. While the recommended slope is 1:100, in practice it is difficult to build a base for channels that is sufficiently true to enable nutrient films to flow without accumulating in locally depressed areas. Therefore, it has been recommended that slopes of 1:30 to 1:40 be used. The general guideline is that the flow rates for each gully should be 1 litre per minute. Flow rates beyond these extremes are often associated with nutritional problems. Depressed growth rates of many crops have been observed when channels exceed 12 metres in length. Also ensure that there is adequate air circulation at the root zones. Moulds and pathogens are prone to grow in moist environment, so a regular check on the condition of your plants in NFT system will help you to spot the early signs of pests and diseases. To prevent your plants from Pythium infection, it is better to add H2O2 to your solution.
The advantages of using NFT system over other hydroponic systems are:
- The plant roots are exposed to adequate supplies of water, oxygen and nutrients. In all other hydroponic systems, there is generally a conflict between the supplies of these requirements, since excessive or deficient amounts of one of the factors results in growth imbalance.
- High yields of high-quality produce are obtained over an extended period of cropping.
However, on the downside, NFT has very little buffering against interruptions in the flow, e.g. power outages, but, overall, it is one of the more efficient techniques.