2019 ASHS Annual Conference

Food safety, environmental impact, and efficient energy usage are growing concerns in horticultural production systems. Using artificial lighting in producing chili pepper and green onions could be a solution to address these concerns. The objective of this study was to compare the effects of LED lighting and fluorescent lighting on the growth of young Hawaiian chili pepper plants and 'Koba' green onion plants in a noncirculating hydroponic system. Chili pepper (Capsicum frutescens L. 'Hawaiian') seeds were started in Oasis® cubes under T5 high output fluorescent lighting in the lab. Seedlings were then transferred to 5.1-cm net pots, which were placed in 1.9-liter containers containing a hydroponic nutrient solution of Hydro-Gardens' Chem-Gro lettuce formula 8-15-36 hydroponic fertilizer with added calcium nitrate (19% Ca and 15.5% N) and magnesium sulfate (9.8% Mg and 12.9% SO₄). Half of the seedlings were grown under red+blue+white LED lighting and half under T5 high output fluorescent lighting (99 µmol/m²/s, 12-h photoperiod). 'Koba' green onions (Allium fistulosum L.) seeds were started as previously described. Seedlings were grown under T5 high output fluorescent lighting, 1.7:1 ratio blue:red LED lighting, or red LED lighting (119 µmol/m²/s, 12-h photoperiod). At the end of the study, for chili pepper plants, stem diameter 1 cm above the Oasis cube surface was significantly greater with the LED lighting than the fluorescent lighting. There were no significant differences in plant height, SPAD reading, leaf dry weight, stem dry weight, root dry weight, and total plant dry weight. In addition, there were no significant differences in partitioning of dry weight into leaves, stems, and roots. For green onion plants, plant height and leaf dry weight were greatest with the red LED lighting, with no significant differences between the blue:red LED lighting and fluorescent lighting. Plants under fluorescent lighting grew tipped over or leaning over, while plants under the red LED lighting grew upright. Plants under the blue:red LEDs showed a mixed response with some plants leaning over and some plants upright. In conclusion, red+blue+white LED lighting could be an alternative lighting source to fluorescent lighting for young Hawaiian chili pepper plants. Red LED lighting enhances growth of young 'Koba' green onion plants.