Effects of low Pre-Night Temperature on Microclimate, Fruit Yield, and Energy Consumption of Greenhouse Tomatoes Grown with a Raised-Trough Production System

Abstract

The effects of two low pre-night temperatures with temperature integration (TI) on the plant growth, fruit yield, microclimate, and energy of greenhouse tomatoes (Big-Dina, Macarena, and Clarance) were investigated. For new TI regime, a pre-night low air temperature of 13C was purposefully applied for three hours (18:00-21:00) while an overall target for daily average temperature of 18.25C was maintained by adjusting temperature in other three time periods of the day. For the control TI, a pre-night temperature of 17C was maintained with an exact same target daily average temperature of 18.25C. With the New TI regime, average vertical air and leaf temperatures were 0.40-0.50C and 0.26-0.46C, respectively, lower than control TI, while relative humidity was 2-3% higher than control TI. The energy consumption with new TI was 3-5% lower than control TI regime. There was no significant difference in growth parameters between two TI regimes in all three cultivars. New TI regime increased fruit temperature in comparison to leaf temperature which stimulated higher fruit growth. As of the results, early yields with new TI were about 75%, 32%, and 39% higher than control TI for Big-Dina, Macarena, and Clarance, respectively. Total marketable yield over the whole experimental period was 13% higher for Big-Dina with new TI, while the yield was similar between two TI regimes for Clarance and Macarena. The new TI regime did show a potential for higher total yield for Big-Dina, higher early yield for all three cultivars, and increased energy use efficiency.