Latest development in lighting greenhouse vegetables

Year-round production is important for providing high quality produce to consumers, for maintaining/increasing market share, and for competing successfully in national and international markets. Because of the low natural light condition during the winter in Canada, artificial light is needed to supplement natural light for year-round greenhouse fruit vegetable production. Supplemental lighting not only increases light intensity in the greenhouse but also adds significant amount of energy into the greenhouse, affecting greenhouse energy balance and microclimate. It is more economical to use long photoperiod (up to 24-h) of low intensity lighting because it can reduce the capital cost for light fixtures, and allow more efficient use of the heat released from the light fixtures, more uniform microclimate which prevents fungal diseases, and the application of blackout curtain to prevent light pollution. However, lighting longer than 17-h causes significant injury on greenhouse fruit vegetables. In this presentation, the research leading to the discovery of alternating red and blue LED light strategy is discussed, The strategy allows for injury-free production of greenhouse tomatoes with 24-h (continuous) lighting. The heat (convective and radiative) output and spectral composition from various supplemental light sources (such as high pressure sodium lamps (HPS), LEDs, hybrid of HPS and LEDs) are different, which results in different microclimate. As of the results, the greenhouse heating, climate control and crop management need to be adjusted to optimize crop production under various lighting sources. Therefore, in his presentation, The results from pepper trials under various light sources (HPS, LED, and hybrid of LED and HPS) and proper climate control and crop management strategies under the light sources were discussed. The sustainable yield-round pepper production system with lighting achieved a very high yield (40kg/m2).