subject: What Is Nft Or Nutrient Film Technique? [print this page] The Nutrient Film Technique (NFT) was invented in England way back in the 1970's. The actual motivation was to save the good old British Glasshouse industry from cheaper European imported vegetables that were arriving in the UK. The system had to be inexpensive to produce crops, and inexpensive and easy to setup.
The ideal system had to be one with which the nutrient solutions should be the only actual cost for running (except for the minimal pump power required) and there should be a minimal requirement for cleaning and low labour costs. NFT proved to be one of the best, and still remains the system of choice for most commercial hydroponic cultivation.
N.F.T is very simple with minimal cleaning requirements and low labour costs. The principal it is based upon is a series of channels that provide constant flowing water, oxygen and nutrients to the plants. This flow has a depth in the channels of about 1mm so it's not massive flow or stream. Its rather more like a film of liquid nutrient solution that supplies the plant. This method provides oxygen rich water and nutrients thereby providing the plants continuously with oxygen rich nutrients which enhances growth rates and produces healthy quick growing crops.
In order to ensure that the roots are in constant contact with the nutrient, the solution is pumped from a tank up through the feed-line and delivered into the ends of the gully via micro tubes. Usually there are two of these feeding each gully. If one tube becomes blocked for some reason the second tube will continue to deliver at least some nutrient solution to the plants.
Inside the NFT gully the nutrient solution slowly moves along the channel and the plants have access via capillary action. (The NFT gullies are slightly elevated at the end where the solution enters.) When the nutrient solution reaches the lower end of the gully the solution is collected in a drain box and returned back to the main tank. It continuously recycles through the system.
With an N.F.T system it really is quite important to check nutrient and pH levels on a regular basis. This can be performed with a pH/EC meter which will perform both functions, or if you wish the nutrient solution can be replaced every week. The usual flow rates in N.F.T systems are 750ml to 1 litre per minute with the slope of 1:40 (25mm drop every metre).
To check this, take a one or two litre measuring jug, remove the two micro tubes out of the end of the gully and start filling the jug. It should take one about minute to fill to the one litre mark on the jug. You can easily make adjustments by installing a gate valveopening will increase pressure and closing will decrease pressure.
The size of the gully is dependent on what crop you will be growing, the size the plants will achieve and length of the crop cycle. As an example, most lettuce varieties use the 100mm x 50mm channel because lettuce has a short crop cycle so it doesn't need a huge root zone area. Herbs, strawberries and lower crop types would require the 150mm x 85mm gully because they have a larger root zone and longer crop cycle. The larger size NFT channel (250mm x 85mm) is suited mostly to tomatoes, cucumbers and crops with large root systems.
Another positive with an N.F.T system is that large amounts of growing media are not required. This reduces turnaround time and operating costs for each crop. Some larger crops may require support by way of pots with a small amount of media in them like perlite, rockwool or expanded clay.
Youll discover that there are very few problems with this system. The main thing to watch out for are root zone diseases like Pythium (root-rot). This can happen when the roots of the plants become too large for the gully and begin to dam it up, causing waterlogged roots. Cells death begins to affect the root system and it begins to die from a lack of oxygen. The roots will begin to turn brown and the plant will yellow off. So its very important to choose the right gully size for the plant type you intend to grow. Many people place an air stone into the reservoir and use a small aquarium pump to deliver extra oxygen to the solution.
Conclusion - Nutrient Film Technology (NFT) is quite easy to maintain, has low running costs and is relatively problem free. This is a great system for anyone with a little bit of experience in hydroponics who has a small area of perhaps two square meters or more to dedicate to the their crop. Of course once you have greater experience you can work with larger areas.
