Wetted Weight (Wet Bulk Density)

What wetted weight is

Wetted weight (or wet bulk density) describes the mass of soil or substrate after water has filled its pore space.

It reflects: - Water holding capacity - Pore structure - Drainage characteristics

Why it matters

Wetted weight influences: - Container load and handling - Root oxygen availability after irrigation - Drainage speed - Risk of saturation stress

A substrate with low dry bulk density can still become very heavy when wet.

Practical implications

• Heavier wetted weight means slower drainage
• High wetted weight reduces air-filled porosity after irrigation
• Light substrates may still hold large volumes of water

Common misunderstandings

• “Light” does not always mean “free draining”
• Wet behaviour is often more important than dry feel

Agronomic note

Plants experience the root zone when wet, not when dry.