2017 ASHS Annual Conference

High light interception area (large canopy) is very important to increase whole plant photosynthesis and light use efficiency in early stage of plant growth when plant canopy is small, especially for greenhouse fruiting vegetables (tomatoes, cucumbers and sweet peppers) grown with supplemental lighting. The plants grown under intensive HPS (high pressure sodium lamps) light tend to have shorter internodes, small and more compact canopy, which may limit the light interception at early stage of plant growth. Far-red light has been known for increasing plant height (internode length) and leaf size, and thus could be used for improving canopy growth, light interception, and crop productivity in greenhouse fruiting vegetables grown under HPS lighting. Therefore, we initiated a 3-year project in 2014 to investigate the effects of far red LED light on plant growth, fruit yield and quality of greenhouse tomatoes, cucumbers and sweet peppers. The experiments were conducted in a large greenhouse over 3 winters (one winter for each type of vegetables). Four top far-red LED light treatments, which provided 0 (control), 8, 16, and 24 µmol m^-2 s^-1 of far red photon flux, were applied to 16 plots in a Latin-square design with 4 replications. Overhead HPS (high pressure sodium) lamps provided 160 µmol m^-2 s^-1 of photosynthetic active radiation (PAR) to all the plots in the greenhouse. It was found that the response to far-red light was different among the 3 types of fruiting vegetables. Tomatoes and sweet peppers usually having slow canopy growth had much larger response to far-red light than cucumbers usually having fast canopy growth. Far-red light increased internode length and plant height in both tomatoes and sweet peppers but not much in cucumbers. Far-red LED light increased fruit yield, fruit size and carotenoid content in early tomato production. Therefore, this study clearly demonstrated some beneficial effects of far-red LED light on fruiting vegetables grown under HPS lighting in early production period, especially for tomatoes.