1. What is Vapor Pressure Deficit (VPD)?

Definition: VPD measures the difference between the amount of moisture in the air and how much moisture the air can hold when saturated.

Purpose: It's crucial for understanding plant transpiration rates, greenhouse climate control, and various agricultural applications.

2. How Does the VPD Calculator Work?

The calculator uses the formula:

Where:

• \( VPD \) — Vapor Pressure Deficit (kPa)
• \( T \) — Temperature (°C)
• \( RH \) — Relative Humidity (%)
• \( \exp \) — Exponential function

Explanation: First calculates saturation vapor pressure (SVP) from temperature, then determines the actual vapor pressure from RH, with VPD being the difference.

3. Importance of VPD Calculation

Details: Proper VPD levels are essential for optimal plant growth, affecting transpiration, nutrient uptake, and disease resistance.

4. Using the Calculator

Tips: Enter temperature in Celsius and relative humidity as a percentage (0-100%). The calculator handles the complex exponential calculation.

5. Frequently Asked Questions (FAQ)

Q1: What's the ideal VPD range for plants?
A: Typically 0.8-1.2 kPa for most plants, but varies by species and growth stage.

Q2: Why use VPD instead of just humidity?
A: VPD accounts for both temperature and humidity, giving a more accurate measure of plant stress.

Q3: How does temperature affect VPD?
A: Higher temperatures increase the air's moisture-holding capacity, generally increasing VPD at the same RH.

Q4: What does a high VPD indicate?
A: High VPD means the air is very dry relative to its temperature, causing plants to transpire more.

Q5: How can I adjust VPD in my greenhouse?
A: Increase humidity (humidifiers) or decrease temperature to lower VPD; decrease humidity (dehumidifiers) or increase temperature to raise VPD.