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 metric in agriculture and environmental science for understanding plant stress and transpiration rates.

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 actual water vapor pressure and the saturation water vapor pressure at a particular temperature.

3. Importance of VPD Calculation

Details: VPD is crucial for understanding plant water relations, managing greenhouse environments, and predicting plant stress. It affects transpiration rates and plant growth.

4. Using the Calculator

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

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 does temperature affect VPD?
A: Warmer air can hold more water vapor, so SVP increases with temperature, which affects VPD calculations.

Q3: Why is VPD better than RH alone?
A: VPD accounts for both temperature and humidity, giving a more complete picture of plant water stress than RH alone.

Q4: What's the relationship between VPD and transpiration?
A: Higher VPD generally increases transpiration rates as the gradient for water vapor loss from leaves increases.

Q5: Can VPD be negative?
A: No, VPD ranges from 0 (air is saturated) to SVP (air is completely dry).