The 2012 ASHS Annual Conference

The industry is interested in cost-effective and energy-efficient sources of light to provide adequate growing conditions for greenhouse vegetable production. An experiment is being conducted to evaluated light-emitting diodes (LEDs) as an alternative lighting source for the propagation of greenhouse-grown tomatoes. Six tomato cultivars are grown monthly throughout a year for three weeks in a glass-glazed greenhouse. Five lighting treatments are being tested: natural light (control), natural + supplemental light from a 100-W high-pressure sodium (HPS) lamp, or natural + supplemental LEDs using either 80% red and 20% blue, 95% red and 5% blue, or 100% red. A variant solar daily light integral (DLI) occurs naturally for all treatments, and a constant DLI of 5 mol·m^-2 per day is provided to the seedlings receiving supplemental lighting. Results for different growth parameters will be compared across seasons to determine when supplemental lighting is needed for acceptable plant growth and at what point of the year it is necessary to supplement with blue light. Shoot biomass production per kW-h of energy consumed will be compared for the different treatments. Preliminary findings from this experiment will be presented. This project is supported in part by NIFA SCRI grant 2010-51181-21369.