SUPPLEMENTAL LIGHTING FOR GREENHOUSE-GROWN TOMATOES: INTRACANOPY LED TOWERS VS. OVERHEAD HPS LAMPS

Intensive year-round local production of greenhouse-grown vegetables requires the use of supplemental lighting (SL) to offset seasonally limited solar radiation in northern climates. Intracanopy light-emitting diode (IC-LED) towers were compared to overhead high-pressure sodium lamps (OH-HPS) as alternative SL sources for high-wire greenhouse tomato (Solanum lycopersicum L.) production. Two consecutive experiments evaluating growth, yield, and energy consumption from winter-to-summer (increasing solar daily light integral (DLI); Expt. 1) and from summer-to-winter (decreasing natural DLI; Expt. 2) were conducted in a northern climate (40°N. latitude, West Lafayette, IN, USA) to evaluate crop responses to supplemental photosynthetic lighting. Commercial cultivars ‘Komeett’ and ‘Success’ were grown in a glass-glazed greenhouse for 5 months each time. Plants were grown under one of three lighting treatments that included the following: 1000-W (Expt. 1) or 600-W (Expt. 2) OH-HPS lamps vs. IC-LED towers (95% red + 5% blue) vs. no SL (control). No differences were observed between cultivars for any yield parameter evaluated. Equivalent increases in fruit number and yield were achieved with the two SL treatments compared to the unsupplemented controls. Furthermore, our experiments indicated significant energy savings using IC-LED SL compared to standard OH-HPS treat¬ments (75% and 55% for Expts. 1 and 2, respectively), suggesting that IC-LED SL is a viable alternative to widely adopted OH-HPS SL for energy-efficient greenhouse high-wire tomato production.