Comparison of Light-emitting Diode Towers Versus High-pressure Sodium Lamps for Year-round Production of High-wire Greenhouse-grown Tomatoes

Intensive year-round local production of greenhouse-grown vegetables requires the use of supplemental lighting to complement solar radiation in light-limited northern climates. Intracanopy light-emitting diode (ICL-LED) towers were compared to overhead high-pressure sodium lamps (HPS-OH) as an alternative supplemental light source for high-wire greenhouse tomato (Solanum lycopersicum L.) production. Two consecutive experiments evaluating growth, yield, and energy consumption from winter-to-summer (increasing natural daily light integral (DLI); Expt. 1) and summer-to-winter (decreasing natural DLI; Expt. 2) were conducted in a northern climate (West Lafayette, IN, USA) to evaluate climatic responses to supplemental photosynthetic lighting. Cultivars Komeett and Success were grown in a glass-glazed greenhouse for five months. Plants were grown under one of three lighting treatments which included: 1000-W (Expt. 1) or 600-W (Expt. 2) HPS-OH lamps vs. LED-ICL towers (95% red and 5% blue) vs. no supplemental lighting (control). No differences were observed between cultivars for any of the parameters evaluated. Our findings indicate that equivalent increases in fruit number and yield can be achieved with the two supplemental light treatments compared to the unsupplemented control. Furthermore, significant energy savings can be achieved using the ICL-LED compared to the standard OH-HPS lamps (75% and 55% for Expt. 1 and Expt. 2, respectively). Our results suggest that ICL-LED is a viable alternative to the widely adopted HPS-OH lighting. This project is supported in part by NIFA SCRI grant 2010-51181-21369.