Measurement of field respiration is critical in studies of soil C and N dynamics and greenhouse gas emissions. CO2 concentrations in soil can vary rapidly and widely by factors such as tillage, fertilization, and rainfall, and are subject to both diurnal and seasonal variations. The objective of this study was to compare CO2 concentrations measured by sensors at 7 soil depths (0, 10, 20, 30, 40, 50, 60 cm) with soil gas samples collected at the same depths and analyzed by gas chromatography (GC) in two treatments, with and without corn (Zea mays L.) roots, during the growing season. Soil CO2 fluxes at the soil-air interface were measured using the chamber-based flux technique. The impacts of corn root activity on the concentrations and fluxes of CO2 were documented in two years of corn growth on a Waukegan silt loam soil at the University of Minnesota Rosemount Agricultural Experimental Station, Rosemount MN. Both sensor and GC data indicated high soil CO2 concentrations coincided with high soil temperatures during the corn maturation period. Once corn senescence began, the soil CO2 concentration differences between corn root treatments diminished to a constant value to the end of the season.