Field Capacity vs Container Capacity

Field capacity

Field capacity describes the water content of a soil after excess water has drained freely under gravity in an open field.

It reflects: - Soil texture - Structure - Depth and profile continuity

Container capacity

Container capacity describes the water content after drainage from a container.

Key differences: - Gravity drainage is limited by container height - Perched water tables form at the base - Containers retain more water than soils of the same material

Why the distinction matters

A substrate that performs well in the ground may: - Hold too much water in containers - Have insufficient air-filled porosity - Create chronic oxygen stress

Practical implications

• Container-grown crops experience wetter root zones
• Irrigation timing must account for container behaviour
• Drainage layer depth strongly affects container capacity

Key concept

Container capacity is not field capacity in a pot — physics is different.