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, optimizing greenhouse environments, and predicting evapotranspiration rates in ecosystems.

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: Most plants thrive at VPD between 0.8-1.2 kPa. Values below 0.4 kPa may indicate too much humidity, while above 1.6 kPa may cause plant stress.

Q2: How is SVP determined?
A: SVP is temperature-dependent and can be calculated using the Arden Buck equation or looked up in standard tables.

Q3: Why is VPD better than RH alone?
A: VPD accounts for both temperature and humidity, giving a more accurate measure of the driving force for evaporation.

Q4: What's the relationship between VPD and transpiration?
A: Higher VPD increases transpiration rates as plants lose more water to the drier air.

Q5: How does VPD affect plant growth?
A: Optimal VPD promotes healthy stomatal opening for photosynthesis while preventing excessive water loss.