1. University of Bonn Center for Development Research Genscherallee 3 53113 Bonn Germany
2. University of Bonn Institute of Crop Science and Resource Conservation Karlrobert-Kreiten-Strasse 13 53115 Bonn Germany
3. Nepal Agricultural Research Council Soil Science Division Kathmandu Nepal
4. University of Hohenheim Institute of Crop Science, Department Quality of Plant Products Emil-Wolff-Str. 25 70599 Stuttgart Germany