Growth Stage–Specific VPD Targets
Why VPD targets change with growth stage
Plant sensitivity to VPD varies with:
- Leaf area
- Root system development
- Transpiration demand
- Sink strength
A single “ideal VPD” does not exist.
Establishment and young plants
Characteristics
- Small root systems
- Limited buffering capacity
- High sensitivity to stress
VPD considerations
- Lower VPD preferred
- Excessive VPD causes rapid dehydration
- Very low VPD increases disease risk
Focus: gentle transpiration without stress.
Vegetative growth
Characteristics
- Expanding leaf area
- Increasing transpiration
- High nutrient demand
VPD considerations
- Moderate VPD promotes nutrient flow
- Balance transpiration and water uptake
- Avoid extremes that limit photosynthesis
Focus: steady growth and canopy development.
Flowering and fruit set
Characteristics
- High sink demand
- Calcium and boron transport critical
- Stress-sensitive phase
VPD considerations
- Stable, moderate VPD essential
- Avoid sharp fluctuations
- Extremes reduce fruit set and quality
Focus: consistency and transport efficiency.
Fruit fill and maturation
Characteristics
- Strong sink activity
- Carbohydrate accumulation
- Structural integrity important
VPD considerations
- Slightly higher VPD may be tolerated
- Excessive VPD increases stress and disorder risk
- Low VPD reduces calcium movement
Focus: maintaining balance while supporting yield.
Agronomic note
VPD targets must be adjusted alongside:
- Temperature
- Root-zone condition
- EC and water availability
Key concept
VPD management is dynamic, not static.