1. Faculty of Agricultural and Environmental Sciences; Univ. of Rostock; Justus-von-Liebig-Weg 6 18059 Rostock Germany
2. Dep. of Agroecology, Faculty of Science and Technology; Aarhus Univ.; Blichers Allé 20 DK-8830 Tjele Denmark
3. SEGES Landbrug & Fødevarer F.m.b.A.; Agro Food Park 15 DK-8200 Aarhus N Denmark