Martin Leue (ZALF Müncheberg, Germany), Ruth Ellerbrock & Horst Gerke
"Local-scale distribution of organic matter composition and wettability at surfaces of preferential flow paths"


Surfaces of preferential flow paths in structured soils consist of clay-organic coatings on soil aggregates or linings on biopores. The outermost layer of such surfaces is mostly covered by organic matter which finally controls wettability and sorption properties that are relevant for transport along the flow path. The objective of this study is to compare the local 2D distribution of soil OM composition at intact aggregate and biopore surfaces with that of the wettability. Intact surfaces of aggregated soil samples were scanned using a DRIFT mapping procedure. Wettability was observed by means of contact angle measurements. In contrast to the uncoated surface areas, organic coatings on worm burrows and root channels show relatively higher CH/CO-ratios that correspond with longer water drop infiltration. Both, the OM composition of coatings along preferential flow path surfaces and the water repellence are spatially variable at this local scale.