Introduction to the NFT System
The NFT (Nutrient Film Technique) is a high technology crop production system, and requires both skill and experience from its users if the best results are to be obtained.
NFT achieves high production and product quality through its effects on crop nutrition and water relations and by providing its users with additional opportunities to influence plant growth and development in more productive ways than can be achieved in older types of conventional culture. A thorough knowledge of crop cultural practices and especially of environmental control is needed, and NFT of itself will not overcome deficiencies in the users knowledge in these areas. The prospect of changing from conventional culture methods such as growing in soil to the high technology NFT system is very daunting to many experienced growers. These misgivings are usually overcome by installing a small trial system as described in Section 3. Best results from NFT will be obtained in greenhouses with good environmental control systems. Soil quality and fertility is of no consequence and NFT is suitable for use in older greenhouses where soil has been damaged by disease or mismanagement. Adequate supplies of water are essential In New Zealand very few water supplies are of such low quality that they cannot be used for NFT production. The cost of operating NFT systems is increased when water of low quality is used.
General Features of All NFT systems
Every NFT installation contains channels or gullies in which the plants grow in a shallow film of flowing nutrient solution. NFT gullies are usually, but not always, folded lengths of black and white polythene (often called Panda Film) laid on a carefully prepared sloping firm surface and folded to make an inverted V shaped channel. The nutrient solution flows out of the ends of the gullies into collecting pipes and from the pipes into a sump. Pumps are used to circulate the solution from the sump through flow mains and headers into the gullies.
This 25,000 litre sump serves a 3,760 m2 tomato greenhouse.Behind the sump are the two circulating pumps and tanks for the stock solutions
Fresh water is added to the sump to replace water evaporated by the crops. Additional nutrients are added as nutrient stock solutions to the sump to replace nutrients absorbed from the nutrient film by the crop. The nutrient solution in the sump is kept within a certain range of acidity (solution pH) and within a certain range of nutrient salts concentrations, (the solution conductivity). All of the above features are common to both the NFT trial system and full scale commercial NFT systems.
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