Vapor Pressure Deficit (VPD) Explained

By Sidhanth Pereira
May 24, 2024·2 mins
Vapor Pressure Deficit (VPD) Explained

Understanding Vapor Pressure Deficit: A Key to Thriving Produce

Vapor Pressure Deficit (VPD) is a critical concept in horticulture that refers to the difference between the amount of moisture in the air and the maximum amount the air can hold when saturated. It's a measure of how 'thirsty' the air is for water, which directly affects plant transpiration and growth.

The Science Behind VPD

VPD is calculated using temperature and relative humidity. Temperature plays a significant role in this process because warm air can hold more moisture than cool air. As the temperature rises, the air's capacity to hold water increases, leading to a higher potential VPD if the relative humidity doesn't also rise. When VPD is low, the air is humid, and plants transpire less. Conversely, high VPD means the air is dry, causing plants to transpire more. Proper VPD management ensures plants maintain optimal water uptake and nutrient transport, crucial for healthy growth.

Importance in Growing Produce

Managing VPD is essential for controlling plant stress and optimizing growth conditions. If VPD is too high, plants can lose water faster than they can absorb it, leading to wilting and reduced growth. Too low VPD can result in inadequate transpiration, causing poor nutrient uptake and increased risk of fungal diseases.

Produce That Benefits the Most

Certain crops, like tomatoes, peppers, cucumbers, and cannabis, thrive with careful VPD management. These plants are particularly sensitive to moisture levels and can achieve better yields and quality when VPD is optimized. For instance, cannabis, which is legal to grow in Canada, benefits significantly from precise VPD control to maximize its potency, yield, and overall health. By maintaining the ideal VPD, growers can ensure robust growth, fewer diseases, and higher produce quality.

Monitoring VPD with EarthOne Plant Monitors

To maintain optimal levels of humidity and temperature, consider using EarthOne Plant Monitors to  visualize your VPD over time. EarthOne also provides smart home integrations so you can control your temperature or humidity automatically.

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Accurately measures the core metrics of your plant – soil moisture, light, temperature and humidity - as well as compound metrics such as Vapor Pressure Deficit (VPD) and Growing Degree Days (GDD).

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