Influence of light spectrum and photoperiod on early seedling development and microgreen yield in cabbage (Brassica oleracea var. capitata) and arugula (Eruca sativa)

Abstract

Controlled Environment Agriculture (CEA) and vertical farming (VF) enable urban food production through artificial lighting and soilless cultivation, reducing transport distances and supporting year-round supply. However, sustainability is strongly affected by the energy demand of LED lighting, making it critical to improve yield per unit of supplied light and energy. Microgreens are well suited to VF systems because they are harvested at an early developmental stage, typically 7 to 21 days after sowing, allowing short production cycles. In this study, nine LED spectra (UV, blue, green, orange, red, far-red, blue-red, blue-red-far-red, and cool-white) were tested under 4, 8, and 16 h photoperiods at constant light intensity, resulting in different daily light integral (DLI) levels, to evaluate their effects on seedling emergence, early development, biomass accumulation, and final microgreen yield in cabbage and arugula. Higher emergence values for cabbage were observed under 16 h blue light, while arugula showed the highest emergence under 8 h green light. In both species, 16 h blue-red-far-red treatment was associated with more compact seedlings and higher dry to fresh biomass ratios. In a second phase, emergence enhancing spectra were combined with the biomass enhancing blue-red-far-red treatment to evaluate microgreen production on soil. This two-stage lighting strategy yielded the highest fresh biomass in both species, 2.189 g for cabbage and 12.56 g for arugula. These findings indicate that tailoring the early light environment through species-specific emergence-enhancing spectra can improve microgreen uniformity and yield in vertical farming systems, while simultaneously enhancing energy-use efficiency and light-use efficiency.