Homepage Markus Weiler


Dye pattern in soils: detecting relevant structures.


Presented at the XXV General Assembly of the European Geophysical Society
Nice, France, 2000.






Morphological structures on the pedon scale, like earthworm channels, cracks and soil aggregates, significantly influence flow processes during infiltration. Cracks or earthworm channels in a low permeable matrix, for example, lead to macropore flow with low interaction (water exchange between macropores and matrix). The same structures in a highly permeable matrix lead to macropore flow with high interaction, whereas a spatially heterogeneous soil matrix (aggregation or texture) induce heterogeneous matrix flow. If the infiltrating water is coloured with a dye tracer, characteristic dye patterns result from these different flow processes.
At different sites, sprinkling experiments on plots of 3 m2 with dyed water were performed and the resultant dye-covered vertical and horizontal soil sections at different locations and depths were prepared and photographed. The photographed sections were then objectively classified into stained areas, non-stained areas and visible macropores (>1 mm2) by means of image analysis techniques. The characteristic dye pattern of different flow processes could be recognised in the classified soil sections using a new identification method. The combination of vertical and horizontal sections enables the detection of relevant morphological structures and allows for a consistent identification of flow processes in soil profiles.