USING MORPHOMETRIC EXPRESSIONS FOR MACROPORES TO IMPROVE SOIL PHYSICAL ANALYSES OF FIELD SOILS

Soil physical measurements in field soils are still essentially based on methodologies which implicitly assume that soils are isotropic and homogeneous. Use of basic physical data, thus obtained, in simulation models of the water regime may yield poor results which cannot be improved by calibration or matching procedures. For example, bypass flow along macropores has a major effect on soil water regimes and cannot be ignored. In this paper, use of morphological measurements of macropores is discussed and illustrated for two purposes: (1) improvement of measurement procedures for basic transport parameters in different soil structures and (2) definition of boundary conditions for the flow system based on the occurrence and continuity of macropores. Patterns of water extraction by roots need particular attention, requiring quantification of "accessible" water in addition to the well established "available" water. Use of relatively simple macro-morphological methods should be encouraged to allow widespread morphological measurements under field conditions. © 1990.