Micropore

Small soil pores typically found within soil aggregates. Water does not drain naturally from micropores (as natural drainage to field capacity occurs with macro-pores) and can be considered as being those which retain water and which are gradually depleted of water as this is used by plants via evapo-transpiration. The classification size of a micropore can vary, being less than 0.075mm, or 0.05mm, in diameter; to no smaller than 0.0002mm for what are termed Storage Micropores or Mesopores; whilst any micropore less than 0.0002mm is classed as a Residual Pore and the water retained in these is unavailable to plants, being help at Permanent Wilting Point.