Shortened Light/Dark Cycles Reduce Costs for Microgreen and Baby Leaf Production Under Artificial Lighting by Maximizing the Use of Off-Peak Hours

The effects of shortened light/dark cycles (8/4 h and 4/2 h) on the growth, productivity, and nutritional value of baby leaf vegetables (borage, fenugreek, pea, and sunflower) and microgreens (arugula, broccoli, mizuna, and radish) were evaluated under controlled environment. Control plants were cultivated under 16/8 h photoperiod. The intermittent lighting influenced the quantitative and qualitative parameters of plant growth and yield (fresh weight, robustness index, dty matter content, nutritional value) , yet plant responses were species specific. It is suggested that plant response to shortened light-dark cycles depends on their tolerance/sensitivity to circadian asynchrony, which occurs when external L/D cycles do not coincide with the endogenous circadian rhythms. In areas with time-of-use electricity rates, scheduling lighting during off-peak hours can significantly reduce production costs. It was shown that shortened light-dark cycles can serve as the basis for cost-effective lighting regimes based on electricity tariffs with peak, standatd and off-peak time bands. Thus, intermittent irradiation regime with customized periods (7/4/9/4 h) has been shown to enhance crop yield and qualty or not affect them under equivalent energy consumption while reducing lighting energy costs by 25-45% compared to conventional 16/8 h photoperiod by maximizing the use of off-peak hours.