Media Ageing Curves

What media ageing is

Media ageing describes how substrates change physically and chemically over time.

Ageing is driven by: - Decomposition - Settling - Irrigation cycles - Root growth - Salt accumulation

Common ageing trends

• Bulk density increases
• Air-filled porosity decreases
• Drainage slows
• Water holding capacity shifts
• Oxygen diffusion declines

Organic vs mineral behaviour

• Organic substrates age rapidly
• Wood-based materials collapse fastest
• Mineral soils change more slowly but compact irreversibly

Agronomic implications

• Media performance at planting is not performance at harvest
• Long-cycle crops are most affected
• Irrigation and nutrition strategies must evolve over time

Key concept

Root zones age — plants do not stay in static environments.