Within the Monitoring project of the program “Greenhouse as Source of Energy”, a climate data exchange project was initiated between four Alstroemeria growers (five greenhouses), to focus on the effects of an energy-efficient greenhouse climate on the occurrence or avoidance of leaf dashes. The hypothesis was that radiation losses on cold nights was a major cause of dashed leaves. Dashes appeared throughout the year; there was no seasonal effect. Greenhouse temperatures as low as 10°C and crop temperature of 2°C below the greenhouse temperature did not always result in dashed leaves. Not enough evidence has been found in low leaf temperature events to support the hypothesis that a double screen prevents dashes. The relation between RH, the VPD, accumulated CO2 and dashes could not be clearly proven, but were found “suspicious”. A day length of 16-17 hours in combination with high lighting intensities is considered suspicious, but the relation with dashes could not be studied. In a small trial conducted in the summer of 2020 at Wageningen UR Greenhouse Horticulture in Bleiswijk in an air-conditioning greenhouse, dashes were generated in two varieties by exposing the plants to a concentration of 1800 ppm CO2 during 2 nights at high intensity LED lighting and at night temperature of 18°C. If the plants were under a foil cage at 95-100% RH, they did not develop dashes. By discussing climate data, growers learn further. They will continue the process of data sharing beyond this project.
|Name||Rapport Wageningen Plant Research|