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 crucial measurement in agriculture and greenhouse management for optimizing plant growth and transpiration.

2. How Does the Calculator Work?

The calculator uses the Aroya 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 critical for understanding plant water stress, optimizing irrigation, and managing greenhouse environments. Proper VPD levels help maximize photosynthesis while minimizing disease risk.

4. Using the Calculator

Tips: Enter SVP in kPa (typically calculated from temperature) and RH in percentage (0-100%). Both values must be valid for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What are ideal VPD ranges for plants?
A: Optimal VPD ranges vary by plant species and growth stage, but generally 0.8-1.2 kPa for vegetative growth and 1.0-1.5 kPa for flowering/fruiting.

Q2: How is SVP determined?
A: SVP is typically calculated from temperature using the Magnus formula or similar equations, though it can also be measured directly.

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

Q4: What happens when VPD is too high or too low?
A: High VPD causes excessive transpiration and potential dehydration. Low VPD reduces transpiration and can lead to disease from excess humidity.

Q5: Can this calculator be used for all plant types?
A: The calculation is universal, but interpretation of results should consider specific plant requirements and environmental conditions.