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 parameter in plant physiology and greenhouse management.

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 transpiration rates, managing greenhouse environments, and optimizing plant growth conditions.

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: Optimal VPD ranges vary by plant species but generally fall between 0.8-1.2 kPa for most crops during the day.

Q2: How does VPD affect plant growth?
A: VPD influences transpiration rates - too high causes water stress, too low can reduce nutrient uptake and increase disease risk.

Q3: How is SVP determined?
A: SVP is temperature-dependent and can be calculated using the Arden Buck equation or looked up in tables.

Q4: Why use VPD instead of RH alone?
A: VPD accounts for both temperature and humidity effects on plant water relations, making it more biologically relevant than RH alone.

Q5: What's the relationship between VPD and temperature?
A: As temperature increases, the air's capacity to hold water vapor increases exponentially, affecting VPD even at constant RH.