1. What is Vapor Pressure Deficit?

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 an important metric in plant physiology and greenhouse management.

2. How Does the Calculator Work?

The calculator uses the VPD equation:

Where:

• \( SVP_{leaf} \) — Saturation vapor pressure at leaf temperature (kPa)
• \( SVP_{air} \) — Saturation vapor pressure at air temperature (kPa)
• \( RH \) — Relative humidity (%)

Explanation: The equation calculates the difference between the water vapor pressure inside the leaf and the water vapor pressure in the surrounding 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 values in kPa and relative humidity as a percentage (0-100%). All values must be valid (SVP > 0, RH between 0-100).

5. Frequently Asked Questions (FAQ)

Q1: What is the ideal VPD range for plants?
A: Most plants thrive at VPD between 0.8-1.2 kPa, though optimal ranges vary by species and growth stage.

Q2: How do I measure SVP?
A: SVP can be calculated from temperature using the Magnus formula or obtained from psychrometric tables.

Q3: Why use leaf temperature instead of air temperature?
A: Leaf temperature often differs from air temperature due to transpiration and radiation effects, making it more accurate for VPD calculations.

Q4: What does high VPD indicate?
A: High VPD indicates dry air conditions that can lead to excessive plant transpiration and potential water stress.

Q5: What does low VPD indicate?
A: Low VPD indicates humid conditions that can reduce transpiration and potentially lead to fungal diseases.