COOLING OF LEAFY VEGETABLES IN GREENHOUSES
Leafy vegetables (especially lettuce) obtained through the summer in Israel suffer leaf burns, caused by both high temperatures and low air humidity. In order to improve products quality, we tested methods to reduce the number of high temp. hours by pulses of water spraying over the canopy in order to obtain simultaneous direct evaporative cooling and increased humidity. The treatments did not reduce much the average temperatures of the air, but canopy temperature and humidity at the close vicinity of the plants was affected. Most of the energy entering the greenhouse is absorbed by the plant and most of it removed as a latent heat. This cooling mechanisms limit plant transpiration so that part of the extra water application for cooling is compensated.
Ben Asher, J., Ephath, J.E., Shomron, M. and Blumberg, D.G. (2008). COOLING OF LEAFY VEGETABLES IN GREENHOUSES. Acta Hortic. 797, 87-94
canopy temperature, CWSI, lettuce, radiation, VPD