water-dynamics → capillary-rise-containers
In containers and slabs, water does not distribute evenly from top to bottom.
Capillary forces dominate, creating predictable moisture gradients that strongly influence root function.
Capillary rise is the upward movement of water through small pores driven by surface tension.
In containers, it determines: - How far water moves upward - Where moisture accumulates - Where roots can function effectively
Containers create a perched water table:
This occurs regardless of container height.
Capillary rise depends on: - Particle size - Pore size distribution - Media uniformity
Fine media: - Higher capillary rise - Higher water retention - Lower air-filled porosity
Coarse media: - Lower capillary rise - Faster drainage - Greater oxygen availability
Roots concentrate where: - Moisture is accessible - Oxygen is sufficient
Excessively wet lower zones: - Limit oxygen - Reduce root activity
Excessively dry upper zones: - Limit water uptake
Effective root volume is often smaller than container volume.
In slabs: - Bottom zones may be saturated - Upper zones may dry rapidly - Nutrient distribution becomes stratified
Uniform irrigation volume does not create uniform root conditions.
Better outcomes come from:
Key mistake: - Assuming roots use the full container profile
Roots only use zones where water and oxygen overlap.