Effects of Light Intensity and Spectrum Mix on Biomass, Growth and Resource Use Efficiency in Microgreen Species

Light spectrum and intensity is one of the key factors in the production of microgreens in controlled-environment agriculture and is directly related to plant growth and biomass accumulation. Hence, the objective of this research study was to investigate the biomass, growth, and resource use efficiencies (RUEs) in 14 different species of microgreen grown in two light recipes with 209.5 (OSRAM LED) and 45 µmol m−2 s−1 (INSTAGREEN LED) with a 16/8 h light/dark photoperiod in a growth chamber. Under both LEDs, fresh biomass accumulation and the SPAD content were highest in sunflower. Nasturtium recorded the maximum hypocotyl length under both LEDs. The leaf area index (LAI) was significantly higher in mungbean under the INSTAGREEN LED compared to other microgreens, while the maximum LAI was measured in lentils under the OSRAM LED. This shows that the two different LEDs had species-specific effects. The RUE of the cheaper INSTAGREEN LED was more efficient in terms of light and energy use efficiency, while OSRAM LED was more efficient in terms of water and surface use efficiencies. Overall, the results showed that different species of microgreens exhibit different responses to fresh biomass accumulation and SPAD contents in the leaves, demonstrating the diversity of their growth responses. Across both LEDs (OSRAM LED and INSTAGREEN LED), the top performing microgreen in terms of biomass accumulation as well as SPAD contents in the leaves was sunflower. Consequently, a high chlorophyll content in sunflower led to a higher biomass production by enhancing photosynthesis.