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 a key 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 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, optimizing greenhouse environments, and preventing plant stress. It affects stomatal opening and water movement through plants.

4. Using the Calculator

Tips: Enter SVP values in kPa (calculated from temperature) and relative humidity as a percentage (0-100%). All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What are typical VPD values for plants?
A: Optimal VPD ranges vary by plant species but generally fall between 0.8-1.2 kPa for most crops during the day.

Q2: How do I calculate SVP from temperature?
A: SVP can be calculated using the Magnus formula or Arden Buck equation based on temperature measurements.

Q3: Why is leaf temperature important?
A: Leaf temperature often differs from air temperature due to transpiration and radiation effects, directly impacting VPD calculations.

Q4: How does wind affect VPD?
A: Wind increases VPD by removing water vapor from the leaf boundary layer, enhancing transpiration rates.

Q5: What VPD is too high for plants?
A: VPD above 1.5-2.0 kPa can cause excessive water loss and stress in many plants, leading to stomatal closure.