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 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 at the leaf surface 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 positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the ideal 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 the day.

Q2: How does VPD affect plant growth?
A: VPD influences transpiration rates - too high causes water stress, too low can limit nutrient uptake and lead to disease.

Q3: How do I measure SVP for leaves and air?
A: SVP can be calculated from temperature using the Magnus formula or obtained from psychrometric tables.

Q4: What units should I use for VPD?
A: kPa is the standard scientific unit, though some applications use hPa or mmHg.

Q5: 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.