Vapor Pressure Deficit (VPD) is the difference between the amount of moisture in the air and how much moisture the air can hold when it is saturated. It is typically measured in kilopascals (kPa). As an example, if the air’s actual vapor pressure is significantly lower than its saturation vapor pressure, the VPD will be high, indicating dry air.
Maintaining an optimal VPD is crucial for plant health and growth in controlled environments such as greenhouses. Correct VPD levels facilitate efficient transpiration, allowing plants to absorb nutrients effectively and minimizing stress, which can lead to increased yields and reduced susceptibility to diseases. Historically, growers relied on intuition and basic environmental controls; however, modern precision agriculture emphasizes the importance of actively managing VPD for consistent and predictable results.