An experiment was conducted to compare the measurement of C mineralization using two different methods.  Headspace gas sampling with analysis using GC was compared to an alkali trap method.  The experiment was conducted with a soil amended with a papermill biosolid (PMB) material at rates equivalent to 0, 27, 54, and 81 t/ha.   The soil was incubated at 25C and C mineralization was measured with both methods over eight sampling periods for a total of 167 days.  Initial results show correlation between the C mineralization measured with the two methods, however significant differences were observed.   We will present modeling parameters for C mineralization with increasing rates of PMB relative to measurement techniques.