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 oil 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.