Tillage and corn residue harvesting impact surface and subsurface carbon sequestration

Corn stover harvesting is a common practice in the western U.S. Corn Belt. This 5-yr study used isotopic source tracking to quantify the influence of two tillage systems, two corn ( L.) surface residue removal rates, and two yield zones on soil organic C (SOC) gains and losses at three soil depths. Soil samples collected in 2008 and 2012 were used to determine C enrichment during SOC mineralization, the amount of initial SOC mineralized (SOC), and plant C retained in the soil (PCR) and sequestered C (PCR - SOC). The 30% residue soil cover after planting was achieved by the no-till and residue returned treatments and was not achieved by the chisel plow, residue removed treatment. In the 0- to 15-cm soil depth, the high yield zone had lower SOC (1.49 Mg ha) than the moderate yield zone (2.18 Mg ha), whereas in the 15- to 30-cm soil depth, SOC was higher in the 60% (1.38 Mg ha) than the 0% (0.82 Mg ha) residue removal treatment. When the 0- to 15- and 15- to 30-cm soil depths were combined, (i) 0.91 and 3.62 Mg SOC ha were sequestered in the 60 and 0% residue removal treatments; (ii) 2.51 and 0.36 Mg SOC ha were sequestered in the no-till and chisel plow treatments, and (iii) 1.16 and 1.65 Mg SOC ha were sequestered in the moderate and high yield zone treatments, respectively. The surface treatments influenced C cycling in the 0- to 15- and 15- to 30-cm depths but did not influence SOC turnover in the 30- to 60-cm depth.