Total and Active Soil Organic Carbon from Long‐term Agricultural Management Practices in West Tennessee

Core Ideas Soil management effects on depth distribution of SOC in southeastern US was studied. Significant response of SOC to long‐term tillage was observed mostly in the surface 5 cm. SOC accumulation was favored by corn and cotton systems than soybean systems down to 22.5 cm. Long‐term cover cropping did not increase total and active SOC. There was a strong and significant positive relationship between total SOC and POXC. Soil organic carbon (SOC) content is strongly influenced by agricultural management practices. Leveraging three long‐term field experiments in Tennessee, this study analyzed the effect of crop rotation, tillage, and cover crops on SOC and permanganate‐oxidizable C (POXC) at various soil depth increments (0–2.5, 2.5–5, 5–7.5, 7.5–10, 10–15, 15–22.5, 22.5–30, 30–45, and 45–60 cm), as well as at the 0‐ to 15‐cm profile. Corn ( Zea mays L.) and cotton ( Gossypium hirsutum L.)–based systems showed increased SOC from 0 to 22.5 cm compared with soybean [ Glycine max (L.), Merr.]–based systems. Additionally, no‐till systems accumulated more SOC than tilled systems from 0 to 5 cm, but cover cropping showed no effects. Results also showed a significant positive relationship between SOC and POXC ( P < 0.0001, r 2 = 0.93). This study revealed that SOC and POXC are strongly influenced by management practices in the surface shallower depth increments of southeastern US croplands.