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 crucial measurement in cannabis cultivation as it affects plant transpiration and growth.

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 water vapor pressure at saturation and the actual water vapor pressure at current humidity.

3. Importance of VPD in Cannabis Production

Details: Maintaining optimal VPD is essential for proper stomatal function, nutrient uptake, and preventing mold or mildew in cannabis plants. Different growth stages require different VPD ranges.

4. Using the Calculator

Tips: Enter SVP in kPa (typically calculated from temperature) and RH in percentage (0-100%). Both values must be valid (SVP > 0, RH between 0-100).

5. Frequently Asked Questions (FAQ)

Q1: What are optimal 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, but varies by strain and conditions.

Q2: How does temperature affect VPD?
A: Temperature directly affects SVP - warmer air can hold more moisture, increasing potential VPD at the same RH.

Q3: 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, increasing disease risk.

Q4: Should I measure VPD at canopy level?
A: Yes, microclimate at plant level is most important. Measure temperature and RH where plants are growing.

Q5: How often should I check VPD?
A: Continuously monitor with sensors, as VPD fluctuates with daily temperature and humidity changes.