Quantification of soil C cycling as influenced by management practices is needed for C sequestration, greenhouse gas mitigation, and soil quality improvement. We evaluated the 10-yr effect of combinations of tillage (no-till, mulch till, and conventional till), cropping systems (cotton-cotton-corn and rye-cotton-corn), and N fertilization source and rate (0 and 100 kg N ha^-1 from NH₄NO₃ and 100 and 200 kg N ha^-1 from poultry litter) on crop residue (stems + leaves) production and soil organic C (SOC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM) at the 0- to 20-cm depth in northern Alabama. Total amount of crop residue returned to the soil from 1997 to 2005 was greater in cotton-cotton-corn than in rye-cotton-corn and greater with poultry litter than with NH₄NO₃. While concentrations of soil C fractions at 10 to 20 cm were not influenced by treatments, SOC content at 0 to 20 cm was greater with poultry litter than with NH₄NO₃ at 100 kg N ha^-1 in no-till and conventional till. This resulted in a C sequestration rate of 510 kg C ha^-1 yr^-1 with poultry litter compared with -120 to 147 kg C ha^-1 yr^-1 with NH₄NO₃. Poultry litter also increased PCM and MBC concentrations at 0 to 10 cm compared with NH₄NO₃. Cropping and fertilization increased SOC, POC, and PCM compared with fallow and no fertilization in no-till. Long-term poultry litter application at 100 kg N ha^-1 increased crop residue production, soil C sequestration, and microbial biomass and activities, indicating improved soil quality compared with inorganic N fertilizer and the responses were similar to the application at 200 kg N ha^-1.