Lighting for greenhouse vegetable production--an overview

At temperate latitudes, growth of greenhouse vegetable crops is well correlated with seasonal shifts in irradiance, which constrains annual production schedules and productivity. Although supplemental lighting would appear to be a potentially useful means of extending seasonal limits, current use of supplemental lighting is largely restricted to propagation and transplant production. Information is scarce concerning the use of supplemental lighting during the main crop growth period. Yield data from trials with lettuce, cucumber, tomato and pepper grown under supplemental lighting are promising, but more information on product quality is needed. Adequate guidelines for the suitable timing, irradiance, spectral energy distribution and seasonal use of supplemental lighting are not yet in place for producing crops, and need to be developed in conjunction with other cultural factors. Supplemental lighting increases the effectiveness of greenhouse carbon dioxide enrichment, but may necessitate adjustments in nutrient and climate management in the greenhouse.Key words: Greenhouse, lighting, vegetables, season extension