Bulk Density

What bulk density is

Bulk density describes the mass of dry soil or substrate per unit volume, including pore space.

It is typically expressed as: - g/cm³ - kg/m³

Bulk density reflects compaction, structure, and porosity.

Why bulk density matters

Bulk density influences: - Root penetration - Water infiltration - Air-filled porosity - Drainage - Oxygen availability - Microbial activity

High bulk density restricts roots and gas exchange.
Low bulk density generally indicates good structure but may reduce stability.

Typical ranges

• Sandy soils: ~1.4–1.7 g/cm³
• Loamy soils: ~1.2–1.5 g/cm³
• Clay soils: ~1.0–1.3 g/cm³
• Organic substrates: ~0.1–0.4 g/cm³

Agronomic interpretation

• Rising bulk density usually indicates compaction
• High bulk density increases risk of waterlogging
• Low bulk density substrates drain freely but dry quickly

Key concept

Bulk density describes how tightly packed the root environment is, not fertility.