Bioponics for lettuce production in a plant factory with artificial lighting

The plant factory with artificial lighting (PFAL) has gained worldwide attention, and the most popular culturing system is hydroponics, in which pure soluble inorganics fertilizers are used. The manufacturing processes of these fertilizers are not environment friendly. A new trend termed ‘bioponics’, using organic fertilizers, was brought to our attention. This study aimed to use two organic fertilizers (BIO N and BIO NK, Swiss Hydroponics Lab.) in a deep-flow-technique (DFT) system in a PFAL producing ‘Frill-ice’, ‘Boston’ and ‘Frilly’ lettuce, with Yamazaki formula (inorganic fertilizer) as the control group. The environmental settings of the PFAL were as follows: photosynthetic photon flux density (PPFD) 200 μmol m^-2 s^-1, day/night temperature 25/18°C; CO₂ concentration 1200 ppm. Our results showed that the control group had the highest fresh mass for ‘Frill-ice’ lettuce. Bioponics treatments greatly reduced the nitrate concentration of all lettuces and increased the fresh mass of ‘Frilly’ lettuce. BIO N was not suitable for ‘Boston’ lettuce. Further studies will be conducted using BIO NK and ‘Frill-ice’ lettuce. Using organic fertilizer in PFAL looks promising; however, whether or not the products of bioponics can be considered organic is still controversial.