Key positions held:

- 2003-Nov.2011 Associate Provost/ Associate Vice President for International Affairs, Virginia Tech
- 1993-2003 Associate Dean, College of Agriculture and Life Sciences, Virginia Tech
- 1991-Nov.2011 Director, Office of International Research, Education, and Development, Virginia Tech; Professor (with tenure), Crop and Soil Environmental Sciences, Virginia Tech
- 1990-1991 Program Leader, Rainfed Lowland Rice Ecosystems, International Research Institute (IRRI), Philippines
- 1986-1991 Principal Scientist, Department of Agronomy, International Rice Research Institute (IRRI), Philippines
- 1967-1989 Department Head, Department of Agronomy, International Rice Research Institute (IRRI), Philippines
- 1964-1991 Rice Scientist, Agronomist/Principal Scientist, International Rice Research Institute (IRRI), Philippines, including visiting Scientist at Purdue University(1971-1972) and UC Davis California( 1978-1979)
- 1962-1963 Post Doctoral Scientist at The Ohio State University, Columbus, Ohio and conducted Research on Fission Products- Organic Matter Complex funded by US Atomic Energy Commission and National Institute of Health.