Comparison of Different Temperature Control Systems in Tropical-Adapted Greenhouses for Green Romaine Lettuce Production

Abstract

The cultivation of lettuce in greenhouses is negatively impacted by high temperatures, especially in hot climates. Therefore, developing an efficient method to regulate the internal temperature of greenhouses is essential to sustain crop productivity throughout the year. This study intends to investigate differential temperature control systems for green romaine lettuce production in the greenhouse. The experiment was conducted in a completely randomized design (CRD) with five replications. The four treatments consisted of (1) control, (2) Fogging + ventilation fan, (3) Fogging + shading, and (4) Fogging + ventilation fan + shading. The different temperature control systems influenced the growth and yield parameters, in which shading operation appears to cause reductions in photosynthetic rate, leading to declines of marketable fresh weight. However, the operation of the fogging and ventilation fan was considered the appropriate method for improving indoor air temperature since this resulted in higher growth and yield and a greater sensory evaluation. Maintaining VPD values between 1.62 and 1.76 kPa and controlling light intensity within the 530–700 mol m−2 s−1 range were recommended to ensure a consistent lettuce yield of 65–82 g plant−1 throughout the year.