The Mediterranean climate, characterized by hot, dry summers and mild, wet winters, presents unique challenges for greenhouse cultivation, particularly for heat-sensitive crops like tomatoes. Effective cooling methods are essential for maintaining optimal growing conditions, ensuring that plants do not suffer from heat stress, which can significantly impact growth, fruit quality, and overall yield. This study investigates the impact of various greenhouse cooling approaches on the growth and yield of tomatoes cultivated under Mediterranean climate conditions.

The research was conducted in a controlled greenhouse environment, where tomatoes were grown using different cooling techniques, including natural ventilation, evaporative cooling, shading nets, and a combination of these methods. The performance of each cooling approach was evaluated based on several parameters, including air temperature, relative humidity, plant physiological responses (such as leaf temperature, stomatal conductance, and photosynthetic rate), and crop outcomes like plant height, fruit set, fruit weight, and total yield.

Natural ventilation, while the most cost-effective method, showed limited effectiveness in reducing internal greenhouse temperatures to levels conducive for optimal tomato growth, particularly during peak summer months. The results indicated that while natural ventilation provided some relief from excessive heat, it was insufficient to prevent heat stress, leading to reduced photosynthetic activity and compromised fruit quality and yield.

Evaporative cooling emerged as a more effective method, significantly lowering greenhouse temperatures and maintaining higher relative humidity levels. This method proved to be beneficial in reducing leaf temperature and improving stomatal conductance, thereby enhancing the photosynthetic efficiency of tomato plants. The improved growing conditions resulted in higher fruit set and increased overall yield. However, the increased water usage associated with evaporative cooling raised concerns about sustainability, particularly in water-scarce Mediterranean regions.

Shading nets offered a simple yet effective solution for mitigating excessive solar radiation, reducing the greenhouse temperature, and protecting plants from heat stress. However, excessive shading was found to negatively impact photosynthesis, leading to suboptimal fruit development. The study suggests that careful selection of shading intensity and materials is crucial to balance light reduction with sufficient illumination for photosynthesis.

The combination of evaporative cooling and shading provided the most favorable conditions for tomato cultivation, demonstrating a synergistic effect in maintaining optimal temperature and humidity levels while reducing the risk of excessive water usage. This combined approach led to the highest yield, with tomatoes exhibiting improved fruit size, weight, and overall quality compared to other methods.