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 plant health 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 plant growth and prevent disease.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What is the ideal VPD range for plants?
A: Optimal VPD ranges vary by plant species and growth stage, but generally falls 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 temperature directly affects SVP and consequently VPD. Higher temperatures typically increase VPD at the same RH.

Q3: Why use Aroya's VPD calculation?
A: Aroya's method provides a straightforward and reliable way to estimate VPD for agricultural applications, especially in controlled environments.

Q4: When should I measure VPD?
A: VPD should be monitored continuously in controlled environments, or at least during key daylight hours for field applications.

Q5: Are there limitations to this equation?
A: This simplified equation assumes standard atmospheric pressure. For high-altitude locations, additional adjustments may be needed.