Soil organic carbon sequestration calculated from depth distribution

Authors: Franzluebbers, Alan

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/9/2020
Publication Date: 3/2/2021
Citation: Franzluebbers, A.J. 2021. Soil organic carbon sequestration calculated from depth distribution. Soil Science Society of America Journal. 85:158-171.

Interpretive Summary: Loss of organic matter from soils in the southeastern US has been extensive due to historical practices of conventional tillage and long fallow periods, resulting in oxidation and erosion. However, conservation agricultural systems (like no tillage, cover cropping, residue management) have been developed and adopted by many farmers in the region and there is likely significant sequestration of soil organic carbon occurring on these farms. Sequestration is the removal of carbon dioxide from the atmosphere and its storage in the soil. A scientist from USDA-Agricultural Research Service in Raleigh NC developed a new method of calculating soil organic carbon sequestration that does not require detailed side-by-side comparisons or lengthy investigations over time. This new method requires multiple depth sampling of the soil profile to determine a mathematical distribution of soil organic carbon. Data from several published research projects showed that this method gives comparable estimates as more traditional approaches, but with much less resource expenditure. This approach can be used on private farms to determine the extent of soil organic carbon sequestration. Farmers can potentially benefit from ecosystem markets that make payments based on the amount of carbon stored in soil. This research will help researchers, agronomic advisors, and farmers to better assess agricultural management.

Technical Abstract: Sequestration of organic C in agricultural soils is necessary to improve soil health to meet the challenges of climate change, diminishing biodiversity, water quality deterioration, and rising demands for food and fiber production. New assessment approaches are needed to quantify how a greater variety of agricultural conservation approaches might be contributing to soil health improvement and soil organic C (SOC) sequestration. In the southeastern US, conservation agricultural management has been repeatedly shown to produce soil-profile SOC with strong depth stratification. Concentration of SOC at the bottom of the plow layer is rarely affected by management due to high decomposition potential, while concentration increases toward the surface in a non-linear manner. Using these observations as an ecological foundation, SOC sequestration was calculated as the summation of SOC stock from this baseline condition at the bottom of the plow layer. Data from several literature sources were mathematically fitted with this new approach for validation. Two on-farm surveys with different agricultural management yielded initial estimates of SOC sequestration using this approach on private farms in the region. The interquartile range of SOC sequestration was 3.7 to 8.2 Mg C/ha for conventional-tillage cropland (n = 44 fields), 13.3 to 27.3 Mg C/ha for no-tillage cropland (n = 96 fields), and 16.0 to 26.2 Mg C/ha for perennial pasture (n = 31 fields). This new approach could be valuable to gain greater reach into the diversity of conservation agricultural systems on different soil types and how they might contribute to SOC sequestration.