NFT is often referred to as ‘pure hydroponics’ because virtually no growing medium is used and roots benefit from unrestricted access to oxygen.
When using Multi-Ducts nutrient solution is constantly pumped up from the reservoir to the roots in the planting channel, any nutrient solution not taken up by the plant flows back into the reservoir ready to be passed over the roots again.
The only growing medium used is whatever the plants were started in, plus a small amount of spreader mat to help spread the nutrient solution over the channel surface. While Grodan rockwool blocks are an ideal starting starting medium and the prefered choice of many growers, in fact compost can be used so long as the plants are well rooted and the compost holds together when removed from the pot. Plants MUST be removed from the pot or the outer sleeve removed from the Grodan block when using NFT systems for effective root development, failing to do so is the main cause of NFT failure along with not having sufficient root mass before transplanting.
Constantly supplying nutrient solution directly to the roots combined with an unlimited supply of oxygen means plants grow faster, are healthier and typically produce 3x more yield than plants grown in pots and hand watered.