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 a key metric in agriculture, meteorology, 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: VPD represents the "dryness" of the air by showing the difference between actual and potential water vapor in the air.

3. Importance of VPD Calculation

Details: VPD is crucial for understanding plant transpiration rates, predicting evaporation, and managing greenhouse environments. It affects plant growth and water requirements.

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 stress plants.

Q2: How does temperature affect VPD?
A: Warmer air can hold more moisture, so temperature affects SVP which in turn affects VPD. Higher temperatures generally increase VPD at the same RH.

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

Q4: What units are used for VPD?
A: VPD is typically measured in kPa (kilopascals), though some use hPa or mb (1 kPa = 10 hPa = 10 mb).

Q5: How is VPD used in agriculture?
A: Farmers use VPD to optimize irrigation, predict plant stress, and manage greenhouse environments for optimal growth conditions.