Supplemental lighting in tomato crop on substrate in Swiss conditions

In recent years, light-emitting diodes (LED) have strongly developed, especially for use in greenhouses. They have various advantages including their efficiency, lifetime, and wavelengths ranging from ultraviolet to infrared. The use of LEDs inside the crop seems to be an interesting approach to increase the productivity of greenhouse tomato crops. At the moment, supplemental lighting is not used on tomato in Switzerland for various reasons including the protection of the market for part of the year and the price of electricity. In order to provide some information for Swiss conditions, an experiment was carried out by Agroscope in 2015 and 2016 to evaluate the interest of LED interlighting in combination or not with high-pressure sodium (HPS) lighting in tomato crop on substrate. The interlighting LEDs significantly increased the yields compared to the control without lighting in 2015 (+9%), with continuous operation from 5 am to 9 pm This increase was not repeated in 2016 with a reduced duration of lighting with LED alone. HPS and HPS + LED still gave higher yield than the control. The combination of HPS lighting over and LED interlighting did not result in the increase of the yield compared to the modality with HPS lighting alone. Lighting has an effect on the yield, but also on the diameter of the plants, which must be taken into account when growing the crop.