Management practices including residue removal, nitrogen (N) application, and crop rotation may impact biomass sorghum productivity and soil organic C (SOC) dynamics. In this study a processed-based model, DeNitrification-DeComposition (DNDC), was used to simulate SOC and N and was compared to observations from a five-year field trial in the Southcentral USA. The experimental results indicated that residue removal, N application, and cropping systems affected both SOC and N. The model predictions were close to or within the range of uncertainties of estimates derived from the measurements. DNDC can be used to predict SOC and N across a range of biomass sorghum production systems.