An enhanced method for using the IPCC approach to estimate soil organic carbon storage potential on U.S. agricultural soils

• Soil organic carbon (SOC) storage estimates for U.S. agricultural land presented.
• 1997 IPCC data and an enhanced IPCC approach developed.
• Land use and management tracked through 3 inventory periods.
• Effect of previous tillage and land use on SOC stocks estimated.
• 3500 unique SOC storage rates estimated with the approach.

The Intergovernmental Panel on Climate Change (IPCC) provides a method to estimate soil organic carbon (SOC) stock changes relative to the SOC stock under native vegetation. This manuscript modifies the IPCC approach to use the ending SOC stock from the previous inventory as the SOC stock that is changed by land use and management activities during the next inventory and to track the crop rotation and tillage intensity through three inventories. The approach allows annual rates of change of carbon sequestration from different historic land uses and management to be estimated explicitly for each assessment point based on the effect of previous land use and management. The model generates 3524 unique annual SOC sequestration rates that vary by land use and management history on U.S. agricultural land based on the 30 SOC stock reference values provided by IPCC documentation. An average of 0.33 Mg C ha−1 yr−1 is stored when cropland that was conventionally tilled in two previous inventories is set-aside in the third inventory, but only 0.14 Mg C ha−1 yr−1 when it is conventionally tilled in the first inventory and no-till in the second inventory before it is set aside. Incorporating a winter cover on cropland that was conventionally tilled in the first inventory and no-till in the second and third inventories is estimated to store 0.49 Mg C ha−1 yr−1, but could store 0.81 Mg C ha−1 yr−1 if it was conventionally tilled in the first two inventories and under no-till in the final inventory. Cropland under conventional tillage in the first two inventories and no-till the final inventory could store an average of 0.34 Mg C ha−1 yr−1, but cropland under conventional tillage in the first, reduced tillage in the second, and no-till in the third inventory is estimated to store 0.19 Mg C ha−1 yr−1. The detailed annual rates of SOC stock change estimated using the approach is useful for economic or other analyses and for policymakers.