1. College of Agriculture and Veterinary Medicine, Jimma University, POB 1316, Jimma, Ethiopia
2. Department of Earth and Environmental Sciences, KU Leuven, Celestijnenlaan 200E box 2411, 3001 Leuven, Belgium
3. Isotope Bioscience Laboratory – ISOFYS, Faculty of Biosciences Engineering, Ghent University, Coupure links 653, 9000 Gent, Belgium