Counterfactual scenarios reveal historical impact of cropland management on soil organic carbon stocks in the United States

Authors: OGLE, STEPHEN - Colorado State University; BREIDT, JAY - Colorado State University; Del Grosso, Stephen - Steve; GURUNG, RAM - Colorado State University; SPENCER, SHANNON - Colorado State University; WILLIAMS, STEPHEN - Colorado State University; MANNING, DALE - Colorado State University

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2023
Publication Date: 9/4/2023
Citation: Ogle, S., Breidt, J., Del Grosso, S.J., Gurung, R., Spencer, S., Williams, S., Manning, D. 2023. Counterfactual scenarios reveal historical impact of cropland management on soil organic carbon stocks in the United States. Scientific Reports. 13. Article e14564. https://doi.org/10.1038/s41598-023-41307-x.
DOI: https://doi.org/10.1038/s41598-023-41307-x

Interpretive Summary: The United States is among a growing number of countries promoting storage of carbon in agricultural soils as part of the climate solution. Scientists from USDA-ARS and Colorado State University sought to understand how climate smart farming practices, including conservation easements under the Conservation Reserve Program, contribute to soil carbon seq formation and an agro-ecosystem they estimated that no-till, cover crops, and CRP removed between 11 and 17 Mt CO2 annually from the atmosphere. Their research highlights the potential to continue to improve carbon sequestration in agricultural soils, but that some of this potential has been realized due to past adoption of climate smart practices.

Technical Abstract: Natural climate solutions provide an opportunity to reduce greenhouse gas emissions and limit future climate change. The United States is among a growing number of countries promoting storage of carbon in agricultural soils as part of the climate solution. Historical patterns of soil organic carbon (SOC) stock changes provide context for evaluating future potentials, and therefore our objective was to quantify the influence of climate smart practices on SOC stock changes in the top 30 cm of mineral soils for croplands in the United States from 1995 to 2015. These practices include winter cover crop management, conservation tillage, hay and pasture in a rotation with annual crops, manure amendments, and setting-aside land from crop production. We conducted this analysis using a process-based model platform and historical management data, and developed a counterfactual analysis by removing climate smart practices from the historical time series to determine their influence on SOC stocks. We estimated that there were net increases in SOC stocks across all years, with the largest increase of 16.8±5.6 Mt C in 1995 and the lowest increase of 10.6±6.1 Mt C in 2015. Most climate smart practices contributed to increases in SOC stocks with the exception of winter cover crop management, which had a negligible impact due to a relatively small area with cover crop adoption. Our study suggests that there is potential for enhancing C sinks associated with cropland soils of the United States although some of the potential has been realized due to past adoption of climate smart practices. To the extent that history is an indicator of the future, agricultural management in the United States may be part of the climate solution, removing CO2 from the atmosphere by storing C in soils, but the historical level of C sequestration would only represent a small part of the total greenhouse gas emission reductions needed to achieve the goal of the Paris Agreement and limit warming below 2°C.