Hydroponics refers to plant roots in direct contact with nutrient solution without substrate cultivation.
British Cooper in 1973 proposed hydroponic nutrient film technique, referred to as the NFT (nutrient film technique). Its principle is making a very thin layer of nutrient solution (0.5-1 cm) , continue to cycle through the crop roots, not only to ensure a continuous supply of crop water and nutrient, but also to ensure a continuous supply of fresh O2. NFT cultivation makes irrigation technology greatly simplified and do not need to calculate crop water requirement, and it can get equilibrium of nutrient supply. The isolation of root and soil, can avoid all kinds of soil borne diseases nor need to sterilize soil.