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 for cannabis growers as it affects plant transpiration and nutrient uptake.

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 in Cannabis Cultivation

Details: Proper VPD levels help optimize cannabis growth by maintaining ideal transpiration rates. It affects stomatal opening, CO2 uptake, and nutrient transport.

4. Using the Calculator

Tips: Enter SVP in kPa (calculated from temperature) and RH in percentage (0-100%). For best results, measure RH at canopy level.

5. Frequently Asked Questions (FAQ)

Q1: What are ideal VPD ranges for cannabis?
A: Generally 0.8-1.2 kPa for seedlings, 1.0-1.5 kPa for vegetative growth, and 1.2-1.6 kPa for flowering.

Q2: How does temperature affect VPD?
A: Warmer air can hold more moisture, so temperature directly affects SVP and thus VPD calculations.

Q3: When should I measure VPD?
A: Continuously monitor VPD as it changes with temperature and humidity fluctuations throughout the day.

Q4: What happens if VPD is too high or too low?
A: Too high causes excessive transpiration and stress; too low reduces transpiration and nutrient uptake.

Q5: Can I use this for other plants?
A: Yes, but optimal VPD ranges vary by plant species and growth stage.