Tillage Effects on Carbon Sequestration and Microbial Biomass in Reclaimed Farmland Soils of Southwestern Indiana

Carbon sequestration in reclaimed mine soils (RMSs) could partly mitigate C emissions associated with coal mining, but our knowledge of C storage in RMSs is derived almost exclusively from studies conducted in restored grasslands and forests. Limited information exists regarding intensively managed RMSs under agricultural land use. A study was conducted to assess the impact of tillage on recent soil organic C (SOC, total organic C minus geogenic C), total microbial biomass C (t‐MBC) and active microbial biomass C (a‐MBC) in RMSs under no‐till (NT, 13 yr) and moldboard plowing (MP, 9 and 13 yr). An undisturbed second‐growth forest and a newly reclaimed (NR, 1 yr) grassland were also included. Significant effects ( P < 0.01) of tillage on SOC, t‐MBC, a‐MBC, and metabolic quotient ( q CO2 ) were detected in the 0‐ to 5‐cm soil layer. These soil properties were strongly ( r 2 > 0.66) correlated with recent SOC, but moderately ( r 2 = 0.21–0.60) with geogenic C. Rates of C sequestration were estimated from the temporal trend in the recent SOC pool (0–40 cm in NR (23.2 Mg C ha −1 ), 9‐yr MP (32.9 Mg C ha −1 ) and 13‐yr MP (33 Mg C ha −1 ), and ranged between 0.8 and 0.25 Mg C ha −1 yr −1 during the first and second decades of restoration. Despite a similar amount of crop residue returned (2.8 Mg C ha −1 yr −1 ), recent SOC under 13‐yr NT (36.8 Mg C ha −1 ) exceeded that under 13‐yr MP by 3.8 Mg C ha −1 This finding, in conjunction with the lower q CO2 in the surface soil layer of NT, suggests a more efficient C utilization by soil microbes under NT than under MP. These results illustrate the benefits of NT to the restoration of SOC stocks and biological properties of severely disturbed soil systems.