1. Department of Plant and Soil Science, Texas Tech University, Lubbock, TX, USA
2. Albrecht Daniel Thaer-Institut für Agrar- und Gartenbauwissenschaften, Humboldt-Universität zu Berlin, Berlin, Germany
3. Department of Earth and Environmental Science, Botswana International University of Science and Technology, Palapye, Botswana
4. Carrrington Research Extension Center, North Dakota State University, Carrington, ND, USA
5. Department of Soil Science, Stellenbosch University, Matieland, South Africa