Where the soil grains are quite free from each other the smaller grains tend to fill up the spaces between the larger ones; hence it might be concluded that in clays the amount of pore-space would be less than in coarser sands.
This is the case in " puddled " clays, but in ordinary clay soils the excessively minute particles of which they largely consist tend to form groups of comparatively large composite grains and it is in such natural soils that the pore-space is largest.
When the pore-space of the soil is filled with water it becomes water-logged and few plants can effect absorption by their roots under such conditions.
Under such conditions each particle of soil is surrounded by a thin film of water and in the pore-space air can freely circulate.
