1. What is the Dr. Greenhouse VPD Equation?

The Dr. Greenhouse method estimates vapor pressure deficit (VPD) from saturation vapor pressure (SVP) and relative humidity (RH). VPD is an important metric in greenhouse and agricultural applications that affects plant transpiration and growth.

2. How Does the Calculator Work?

The calculator uses the Dr. Greenhouse equation:

Where:

• \( SVP \) — Saturation vapor pressure (kPa)
• \( RH \) — Relative humidity (%)

Explanation: The equation calculates the difference between the amount of moisture in the air and how much moisture the air can hold when it's saturated.

3. Importance of VPD Calculation

Details: VPD is crucial for understanding plant water stress, optimizing irrigation, and managing greenhouse environments for optimal plant growth.

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 is a good VPD range for plants?
A: Most plants thrive at VPD between 0.8-1.2 kPa, though optimal ranges vary by species and growth stage.

Q2: How do I measure SVP?
A: SVP can be calculated from air temperature using the Magnus formula or obtained from psychrometric charts.

Q3: Why is VPD important in greenhouses?
A: VPD directly affects plant transpiration rates, nutrient uptake, and overall plant health and growth.

Q4: What happens when VPD is too high or too low?
A: High VPD causes excessive water loss, while low VPD can lead to reduced transpiration and potential fungal issues.

Q5: Can this be used for outdoor agriculture?
A: Yes, the same principles apply, though outdoor environments are harder to control than greenhouses.