Long-term tillage effects on soil carbon storage and carbon dioxide emissions in continuous corn cropping system from an alfisol in Ohio

The experiment designed to quantify the effects of long-term tillage practices on soil organic carbon (SOC) storage and CO2 emissions, was conducted on long-term tillage and continuous corn (Zea mays L.). The experimental plots were established in 1962 on a Crosby silt loam (fine, mixed, mesic Aeric Ochraqualf) in Ohio. It consisted of moldboard plow till (MT) chisel till (CT), and no-till (NT) laid out in a randomized block design with four replications. After 43 yrs of continuous corn, the pool of SOC in the top 30 cm depth was significantly greater under NT (80.0 ± 3.7 Mg C ha−1) than under CT (45.3 ± 1.7 Mg C ha−1) and MT (44.8 ± 3.7 Mg C ha−1). A large proportion (68–74%) of SOC, in the 0–30 cm depth originated from corn residues (C4-C). On average, MT, CT and NT treatments sequestered C4-C in the top 30 cm at a rate of 0.73, 0.71 and 1.37 Mg ha−1 yr−1. The average daily CO2 fluxes (g CO2-C m−2 d−1) were greater under MT (2.14) and CT (2.07) than under NT (1.61). In addition, the daily CO2 fluxes were highest in summer (2.62–3.77 g CO2-C m−2 d−1), the lowest in winter (0.75–0.87 g CO2-C m−2 d−1), and were positively correlated with air (R2 = 0.78, P < 0.01) and soil temperatures in the top 20 cm (R2 = 0.76, P < 0.01) and negatively with soil water content (R2 = 0.57, P < 0.05). Tillage management had a significant influence on average daily CO2 fluxes during summer and autumn but not during winter and spring. Annual CO2 emissions calculated by extrapolating daily CO2 fluxes were significantly higher under MT (6.6 ± 0.3 Mg CO2-C ha−1 yr−1) and CT (6.2 ± 0.4 Mg CO2-C ha−1 yr−1) than under NT (5.5 ± 0.5 Mg CO2-C ha−1 yr−1; LSD = 0.25 Mg CO2-C ha−1 yr−1). These results indicated that, during the growing season, NT reduced CO2 emissions by an average of 0.7 and 0.6 Mg C ha−1 yr−1 compared to MT and CT, respectively.