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 plant growth and greenhouse management, indicating the driving force for plant transpiration.

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 stress, optimizing greenhouse environments, and managing irrigation systems. Proper VPD levels ensure healthy plant growth and prevent issues like mold or dehydration.

4. Using the Calculator

Tips: Enter SVP in kPa and RH as a percentage (0-100%). SVP can be calculated from temperature using various formulas if not directly available.

5. Frequently Asked Questions (FAQ)

Q1: What are optimal 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.

Q2: How does temperature affect VPD?
A: Higher temperatures increase SVP, which can significantly increase VPD at the same relative humidity.

Q3: Why is VPD better than RH alone?
A: VPD accounts for both temperature and humidity, giving a more accurate 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 stress, while low VPD reduces transpiration and can lead to disease.

Q5: How can I adjust VPD in my grow space?
A: VPD can be adjusted by changing temperature (affects SVP) or humidity (affects RH) through heating, cooling, humidification, or dehumidification.