Abstract
Comparison of the effects of supplemental lighting with fluorescent lamps inside the plant canopy on the yield of tomato plants (Solanum lycopersicum L.) was attempted under the following lighting schedules; A) 2 hours around sunrise, B) 2 hours before noon, C) 9 or 10 hours during the daytime, D) 2 hours before noon but only when sunlight was below 200 μmol m-2 s-1, and E) 9 or 10 hours during the daytime but only when sunlight was below 200 μmol m-2 s-1. Supplemental lighting increased yield in all schedules. Schedule C showed the largest increase, followed by B, and A. The limited lighting treatments (schedules D and E) were less effective than the corresponding unlimited treatments (schedules B and C). Schedule C was best in terms of increased yield in this experiment but was not efficient in terms of lighting cost. Schedule B was the most cost-effective option in this experiment but needed more decreasing of lighting costs for practical use.
