Increasing carbon (C) sequestration through no-till (NT) practices can improve air and soil quality. To evaluate the impact of NT continuous corn on biophysical C sequestration processes and/or properties, composite soil (fine, illitic, active, mesic, mollic Epiaqualfs) samples at 0-7.5, 7.5-15, 15-22.5 and 22.5-30 cm depth were randomly collected from 2, 20, and 40 yr NT and their adjoining conventionally tilled (CT) plots in Wood County, northern Ohio. Soil samples were processed and analyzed for concentration and stocks of total organic C (TOC), macroaggregate protected C (MAC), microbial biomass C (MB_C), basal (BR) and specific maintenance respiration (qCO₂) rates with selected basic soil properties. Averaged across, year, the concentration and stocks of MB_C and M_AC in NT soil increased significantly with an associated decrease in qCO₂ compared to CT soil. Temporal effects of NT were more pronounced on MB_C, qCO₂, and M_AC than on BR at different depths of soil. A significant inverse relationship between MB_C and qCO₂ showed an efficient C utilization by soil microbes in NT than in CT. On average, tillage effects on biophysical C sequestration were more pronounced at surface soil than at subsurface soil. Combined over soil depth (0 to 30 cm), the storage of MB_C and M_AC increased significantly in NT soil over CT soil. When plotted the difference of NT-CT mass of MB_C and M_AC pools with time, a significant quadratic increase in sequestration was observed in NT soil. Results suggest that greater C sequestration in NT soil over CT soil is possibly initiated by efficient utilization of C inputs by microbes followed by greater physical protection of C in macroaggregates over time.creasing carbon (C) sequestration through no-till (NT) practices can improve air and soil quality. To evaluate the impact of NT continuous corn on biophysical C sequestration processes and/or properties, composite soil (fine, illitic, active, mesic, mollic Epiaqualfs) samples at 0-7.5, 7.5-15, 15-22.5 and 22.5-30 cm depth were randomly collected from 2, 8, and 40 yr NT and their adjoining conventionally tilled (CT) plots in Wood County, northern Ohio. Soil samples were processed and analyzed for concentration and stocks of total organic C (TOC), macroaggregate protected C (MAC), microbial biomass C (MB_C), basal (BR) and specific maintenance respiration (qCO₂) rates with selected basic soil properties. Averaged across, year, the concentration and stocks of MB_C and M_AC in NT soil increased significantly with an associated decrease in qCO₂ compared to CT soil. Temporal effects of NT were more pronounced on MB_C, qCO₂, and M_AC than on BR at different depths of soil. A significant inverse relationship between MB_C and qCO₂ showed an efficient C utilization by soil microbes in NT than in CT. On average, tillage effects on biophysical C sequestration were more pronounced at surface soil than at subsurface soil. Combined over soil depth (0 to 30 cm), the storage of MB_C and M_AC increased significantly in NT soil over CT soil. When plotted the difference of NT-CT mass of MB_C and M_AC pools with time, a significant quadratic increase in sequestration was observed in NT soil. Results suggest that greater C sequestration in NT soil over CT soil is possibly initiated by efficient utilization of C inputs by microbes followed by greater physical protection of C in macroaggregates over time.