1. University of Bonn, Institute of Crop Science and Resource Conservation (INRES), Soil Science, Nussallee 13, 53115 Bonn, Germany
2. Department of Ecology, Faculty of Environmental Sciences, Czech University of Life Sciences, Kamýcká 1176, Prague 6, Suchdol, 165 21, Prague, Czech Republic
3. University of Bonn, Institute of Crop Science and Resource Conservation (INRES), Crop Science, Katzenburgweg 5, 53115 Bonn, Germany