1. Department of Agroecology; Faculty of Science and Technology, Aarhus University; Blichers Allé 20, PO Box 50 DK-8830 Tjele Denmark
2. Department of Soil, Water and Environmental Science; The University of Arizona; 1177 E. 4th Street Tucson AZ 85721-0038 USA
3. Department of Civil Engineering; Aalborg University; Sofiendalsvej 11 DK-9200 Aalborg SV Denmark