Influence of light emitting diodes as alternative lighting for cabbage (Brassica oleracea var. capitata) microgreens grown under ambient conditions

Artificial lighting is essential in indoor farming, wherein light quality is considered in crop production. In this study, light-emitting diodes (LEDs) using different colours (red (R), blue (B), RB and white (as control) were used to determine the impact on the growth of cabbage microgreens under ambient conditions. A completely randomised design with 4 replications was used. Microgreens were exposed to LEDs for 10 hr and 14 hr in darkness. The microgreens were harvested 10 days after emergence by cutting them from the surface of vermicast (as the substrate) using a sterilised pair of scissors. Results showed that white LED had shorter microgreens and hypocotyls than the other LEDs. Whereas the leaves were longer by exposing the microgreens to blue and RB LEDs than the white LED, the former LEDs showed a similarity with the red LED. A high root count was observed in microgreens with blue and RB LEDs, which was higher than red LEDs. But the white LED showed a similar root count to the other LEDs. Moreover, white LED produced a higher chlorophyll content based on its high SPAD index. Red and RB LEDs produced a higher fresh weight of microgreens than white LEDs. Fresh weight per microgreen had a positive relationship with the fresh weight yield of microgreens. Likewise, microgreen height, hypocotyl length and leaf length displayed a positive and significant association with a high yield of cabbage microgreens. Either red or RB LED is recommended to obtain a higher yield of microgreens for ambient indoor growing conditions.