Harvest time, photoperiod and white light irradiance on yield of red cabbage microgreens in plant factory

Plant factory is a production system characterized by high control and efficiency of the production factors, in which the cultivation of microgreens has increased. Photoperiod and photosynthetic photon flux density (PPFD) are two of the main factors to be investigated in order to obtain maximum yield. In this context, an experiment was conducted in indoor environment to evaluate the influence of photoperiod (12, 16 and 20 h d-1 ) and PPFD (150, 250, 350 and 450 μmol m-2 s-1 ) with two harvest times (4 and 6 d of light) on the growth and yield of red cabbage (Brassica oleracea L. var. capitata L.) microgreens. Early harvest, photoperiod and PPFD affected hypocotyl length (HL), cotyledon area (CA) and yield individually and in interaction. Two-day earlier harvest resulted in reductions of 10.0%, 32.0% and 16.5% in HL, CA and yield, respectively. In general, higher PPFD and photoperiod caused decrease in HL and increase in CA and yield. With the combination of these factors, 315 μmol m-2 s-1 with 20 h light promoted the highest yield of red cabbage microgreens. In one year of production, early harvest promotes a greater number of production cycles and higher yield of red cabbage microgreens (616 kg m-2 ), which was 27% higher than that obtained with harvest carried out 2 d later, when the first leaf appeared.