Greenhouse cooling by a fog system: Effects on microclimate and on production and quality of a soilless pepper crop

Abstract

The influence of greenhouse humidity control on greenhouse microclimate, crop transpiration rate, and yield and fruit quality of a soilless grown pepper crop was studied in a greenhouse located in the coastal area of western Greece. Measurements were carried out during summer and autumn in two distinct compartments involving: (i) no air humidity control and (ii) a fog system operating when the relative humidity of the greenhouse air was lower than 80%. Under fog conditions, the greenhouse air and the crop leaf temperature were about 3°C lower than those measured under no fog conditions. In addition, under fog conditions, the air vapour pressure deficit was lower than 2 kPa, even during the warmest part of the day. Furthermore, the use of a fog system reduced crop transpiration by about 20%. The fog system enhanced the mean fruit weight and the percentage of marketable fruits but reduced appreciably the total number of fruits per plant. The acid content and pH of the pulp juice of pepper fruits were not affected by the fog cooling system, while the soluble solids of the fruits were slightly reduced and the volume of the fruits was increased.