What compaction is
Compaction is the progressive reduction of pore space caused by pressure, settling, and structural collapse.
It affects both soils and substrates.
How compaction develops
- Repeated traffic or handling
- Irrigation-induced settling
- Organic matter decomposition
- Sodium-induced dispersion
- Fine particle migration
Compaction often increases gradually and goes unnoticed.
Effects of compaction
- Increased bulk density
- Reduced air-filled porosity
- Slower drainage
- Restricted root growth
- Reduced oxygen diffusion
Substrates vs soils
- Soils compact mainly from external pressure
- Substrates compact from internal collapse and decomposition
- Lightweight mixes are particularly vulnerable over time
Management strategies
- Avoid working wet soils
- Maintain calcium levels
- Control sodium inputs
- Use structural components in substrates
- Monitor physical properties, not just chemistry
Key concept
Compaction is a time-dependent process, not a single event.