The effects of day and night humidity on yield and quality of glasshouse cucumbers

SummaryThe effects of different day and night humidity levels on autumn- and spring-grown cucumbers were examined in four glasshouse experiments. A high or low humidity during the day was combined with either a high or low humidity during the night to give four treatment combinations. The vapour pressure deficits achieved, over the total period, varied from 0.57 to 0.91 kPa by day, from 0.26 to 0.66 kPa by night, and the 24-h average varied from 0.43 to 0.75 kPa. Temperature differences between the treatments were less than 0.6°C in each experiment. Vegetative growth was enhanced by either high day or night humidity but early yield was not related to either day, night, or 24-h average humidity. A significant negative correlation was found between vapour pressure deficit by day and final total yield in all but one experiment. Fruit quality, expressed as fruit colour, was reduced by a high 24-h average humidity. Calcium deficiency in leaves was correlated with 24-h average humidity. From the viewpoint of production, the best control procedure is to maintain a high humidity during the day but to avoid high 24-h average humidity levels if good fruit quality is to be obtained.