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 agriculture and environmental science.

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 transpiration rates, greenhouse climate control, and predicting plant stress. It affects water loss from plants and evaporation from soil.

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 important in greenhouses?
A: VPD helps manage plant transpiration and prevent issues like edema or excessive water stress in controlled environments.

Q4: What's the relationship between VPD and evapotranspiration?
A: Higher VPD generally leads to increased evapotranspiration rates as the atmospheric demand for water increases.

Q5: Can VPD be negative?
A: No, VPD cannot be negative as it represents a deficit between actual and saturated conditions.