A process-based model using readily available field-scale data to assess long-term effects of cropping systems or crop residue removal on soil organic matter (SOM) accretion/loss in agricultural soils is needed. Originally developed for national use and calibrated initially in the Pacific Northwest, CQESTR has been modified to respond to soil texture and drainage classes nationwide. Other changes include calculating the rate of biological decomposition of organic residue as a function of cumulative degree-days and dividing the surface residue into two compartments reflecting its position and condition. Data inputs include weather, above- and below-ground biomass additions, N content of residues and amendments, soil properties, and management factors such as tillage and crop rotation. The model was recalibrated using information from six long-term experiments across North America (Florence, SC, 19 yrs; Lincoln, NE, 26 yrs; Hoytville, OH, 31 yrs; Breton, AB, 60 yrs; Pendleton, OR, 76 yrs; and Columbia, MO, >100 yrs) having a range of soil properties and climate. CQESTR was then revalidated using data from several additional long-term experiments (8-106 yrs) across North America having a range of SOM (7.3-57.9 g SOM/kg). Regression analysis of 306 pairs of predicted and measured SOM data under diverse climate, soil texture and drainage classes, and agronomic practices at 13 agricultural sites resulted in a linear relationship with an r2 of 0.95 (P < 0.0001) with a 95% confidence interval of 4.3 g SOM/kg. Simulation trends show that management practices that contribute to biomass increase provide annual root and shoot biomass return to the soil, and limit inversion tillage promote SOM accretion. The revised CQESTR model successfully predicts SOM dynamics from various management practices and offers the potential for C sequestration planning for C credits or to guide crop residue removal for bioenergy production while maintaining the SOM level and soil production capacity.