1. Department of Biological Sciences; North Carolina State University; Raleigh North Carolina USA
2. Department of Soil Science; Federal University of Viçosa; Viçosa Minas Gerais Brazil
3. Stanford University Synchrotron Radiation Lightsource (SSRL); SLAC National Accelerator Laboratory; Menlo Park California USA
4. Department of Crop and Soil Sciences; North Carolina State University; Raleigh North Carolina USA