1. Agroscope; Dep. of Agroecology and Environment; Reckenholzstrasse 191 CH-8046 Zürich Switzerland
2. Swedish Univ. of Agricultural Sciences; Dep. of Soil and Environment; Box 7014 SE-75007 Uppsala Sweden
3. Swiss Federal Institute of Technology ETH, Institute of Agricultural Sciences, Crop Science; Universitätstrasse 2 CH-8092 Zürich Switzerland
4. Swiss Federal Institute of Technology, Institute of Terrestrial Ecosystems (ITES), Soil and Terrestrial Environmental Physics (STEP); Universitätstrasse 16 CH-8092 Zürich Switzerland
5. Federal Institute of Technology, Institute of Terrestrial Ecosystems (ITES), Soil and Terrestrial Environmental Physics (STEP); Universitätstrasse 16 CH-8092 Zürich Switzerland
6. Univ. of Lausanne, Institute of Earth Sciences; Applied and Environmental Geophysics Group, Bâtiment Géopolis; CH-1015 Lausanne Switzerland