1. What is Vapor Pressure Deficit (VPD)?

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's saturated. It's a key parameter in greenhouse and plant growth environments.

2. How Does the Calculator Work?

The calculator uses the VPD equation:

Where:

• \( SVP \) — Saturation Vapor Pressure (kPa)
• \( RH \) — Relative Humidity (%)

Explanation: The equation calculates the difference between the water vapor pressure at saturation and the actual water vapor pressure in the air.

3. Importance of VPD Calculation

Details: VPD is crucial for understanding plant transpiration rates, managing greenhouse environments, and optimizing plant growth conditions.

4. Using the Calculator

Tips: Enter SVP in kPa and RH as a percentage (0-100%). All values must be valid (SVP > 0, RH between 0-100).

5. Frequently Asked Questions (FAQ)

Q1: What is a good VPD range for plants?
A: Optimal VPD ranges vary by plant species and growth stage, but generally 0.8-1.2 kPa is good for most plants during vegetative growth.

Q2: How does temperature affect VPD?
A: Temperature affects SVP (higher temperature = higher SVP), which directly impacts VPD calculations.

Q3: Why is VPD important in greenhouses?
A: VPD helps determine when plants will transpire and how much, affecting water uptake, nutrient transport, and overall plant health.

Q4: What's the relationship between VPD and RH?
A: While RH measures how saturated the air is, VPD measures the "drying power" of the air, which is more directly related to plant physiology.

Q5: Can VPD be too high or too low?
A: Yes, too high VPD causes excessive transpiration and stress, while too low VPD can limit transpiration and nutrient uptake.