In modern greenhouse farming, yield and product quality depend on precise control of climate parameters. Relative humidity constitutes one of the most fundamental variables in plant physiology; it directly regulates stomatal conductance, transpiration rate, carbon dioxide assimilation, and photosynthesis efficiency. Stomatal pores on plant leaves open and close according to water vapor pressure in the air, controlling gas exchange. Maintaining ambient humidity at 70-85% ensures stomata remain open, maximizing CO2 uptake and consequently photosynthesis rate.
The vapour pressure deficit concept is the fundamental thermodynamic parameter explaining the effect of humidity in greenhouse climate control. VPD expresses the difference between the maximum water vapor pressure air can carry and the current water vapor pressure. At low VPD values, transpiration slows and nutrient transport through plant roots decreases; at high VPD values, plants encounter stress and close their stomata. The optimum VPD range for tomatoes is accepted as 0.4-1.0 kPa, while 0.3-0.8 kPa is preferred for cucumbers. Precise control of VPD values using industrial humidifiers is the key to yield increase.
Low humidity conditions in greenhouse environments lead to serious physiological problems in plants. Rapid transpiration causes calcium transport imbalance, creating conditions for physiological disorders such as blossom end rot in tomato fruits, fruit curvature in cucumbers, and shape deformities in peppers. Additionally, necrosis development at leaf margins accelerates in low humidity, and the plant's overall stress level increases. Conversely, excessively high humidity creates ideal conditions for fungal disease development, particularly Botrytis cinerea and Cladosporium, especially during nighttime hours.
In greenhouse humidification system design, greenhouse type, covering material, geographic location, and seasonal variations must be considered. Distinct differences exist between glass greenhouses and plastic-covered greenhouses in terms of energy balance and humidity profile. Humidification systems based on evaporative cooling principles at high temperatures both reduce temperature and increase humidity through the adiabatic process; this approach provides energy savings particularly in the Mediterranean climate zone. During winter months, steam humidification working in coordination with heating systems is preferred.
Humidity control gains additional importance in seedling production. Relative humidity of 75-90% in seedling trays containing germinating seeds and young roots supports root development and reduces seedling loss rates. In cut flower greenhouse cultivation, humidity management is one of the factors determining stem length, leaf quality, and vase life. Considering that each plant species has different humidity requirements during vegetative and generative development stages, the humidification system must have flexible and precise control capacity.
As NKT Humidity Control Technologies, we provide expert engineering support for greenhouse and controlled agriculture facility humidity management needs with our industrial humidifier solutions. For humidification system design suitable for your greenhouse conditions, please contact us using the form below.
