Improved red and blue ratio in LED lighting for indoor cultivation of basil

Indoor farming systems are claimed to improve plant resource use efficiency (including water) as compared to traditional growing systems. However, electricity costs associated with plant lighting are still limiting the growth of the sector. Light emitting diodes (LEDs) may provide elevate electricity use-efficiency, while also allowing for adjusting light spectral properties to the plant needs. The goal of this study is to identify the role played by red:blue (RB) ratio on the water and energy resource use efficiency of indoor basil cultivation, linking the light physiological response to changes in yield. Basil plants were cultivated in growth chamber under LED lights supplying 5 different RB ratio regimens (respectively, RB0.5, RB1, RB2, RB3, and RB4) and against fluorescent lamps as control (FL1). In all treatments light supplied provided a PPFD of 215 μmol m-2 s-1 and a photoperiod of 16 h of light per day. Greater biomass production was associated with LEDs lighting as compared with fluorescent lamp, with best performances observed using RB≥2. Adoption of RB2 and RB3 improved also the plant's capacity to transform resources, resulting in greatest energy use efficiency. Decreasing RB ratio increased leaf stomatal conductance, therefore leading to low water use efficiency under RB<2. From this study it can be concluded that a RB ratio of 2 or 3 improves water and energy use efficiency in indoor cultivation of basil.