Impact of wettability distribution on soil rewetting

Benard P.^1*, Bachmann J.², Bundschuh U.³, Cramer A.¹, Kaestner A.⁴, Carminati A.¹

¹Physics of Soils and Terrestrial Ecosystems, Department of Environmental Systems Science, ETH Zürich, Universitätstrasse 16, 8092 Zürich, Switzerland

²Institute of Soil Science, Leibniz Universität Hannover, Herrenhäuser Strasse 2, 30419 Hannover, Germany

³Soil Physics, Faculty for Biology, Chemistry, and Earth Sciences, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Bavaria, Germany

⁴Paul Scherrer Institute, Lab. for Neutron Scattering and Imaging, Forschungsstrasse 111, 5232 Villigen, Switzerland

*corresponding author; pascal.benard@usys.ethz.ch

Plant roots and microorganisms engineer soil physical properties on the pore scale. The accumulation of organic residues in forest soils and the release of exudates alter local soil wettability and by that impact soil rewetting. We captured the capillary driven infiltration of water and ethanol in forest soils and model rhizosphere using time-series neutron radiography. Information on the evolution of local soil water and ethanol content were used to estimate the distribution of wettability employing a 3D pore-network model. Estimates derived by inverse modelling were compared to classic measures of soil wettability and a set of contrasting scenarios regarding their impact on soil rewetting.