7/2007 - present:  Santelmann/Warth Distinguished Professor

Nutrient Management Extension Specialist and the Director of Soil, Water and Forage Analytical Laboratory, Department of Plant and Soil Sciences, Oklahoma State University.
 

7/2004 - 6/2007: Professor and Lab Director, OSU
 

7/2001 - 6/2004: Associate Professor and Lab Director, OSU
 

8/1996 - 6/2001: Assistant Professor and Lab Director, OSU

8/1990 - 7/1996:  Soil Chemist and Lab. Director, Agricultural Testing and Research Laboratory, Navajo Agricultural Products Industry, Farmington, New Mexico.