Quantifying the impact of climate smart agricultural practices on soil carbon storage relative to conventional management

Authors: Schreiner-Mcgraw, Adam; Ransom, Curtis; Veum, Kristen; WOOD, JEFFRY - University Of Missouri; Sudduth, Kenneth - Ken; Abendroth, Lori

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2023
Publication Date: 11/18/2023
Citation: Schreiner-McGraw, A.P., Ransom, C.J., Veum, K.S., Wood, J.D., Sudduth, K.A., Abendroth, L.J. 2023. Quantifying the impact of climate smart agricultural practices on soil carbon storage relative to conventional management. Agricultural and Forest Meteorology. 344. Article 109812. https://doi.org/10.1016/j.agrformet.2023.109812.
DOI: https://doi.org/10.1016/j.agrformet.2023.109812

Interpretive Summary: Climate smart agricultural practices have received considerable attention in recent years for their potential ability to remove carbon dioxide from the atmosphere and store it in the ground. Despite this enthusiasm, there is limited evidence that climate smart practices actually achieve their goal of removing carbon dioxide from the atmosphere. Part of the challenge in evaluating climate smart agricultural practices is that the traditional methods to measure the amount of carbon uptake rely on soil samples, which do not actually measure if additional carbon was removed from the atmosphere. In this study, we hypothesized that a field with aspirational (ASP) practices (i.e., no-till corn-soybean-wheat-hay rotation with cover crops) would accumulate more soil organic carbon (SOC) versus a business-as-usual (BAU) field (i.e., conventional-tillage, corn-soybean-soybean rotation). We used soil samples as well as the state-of-the-art eddy covariance (EC) technique to measure the carbon dioxide removed from the atmosphere. We found that the soil samples and EC techniques agreed that the ASP field had more carbon uptake than the BAU field, but that the magnitude of carbon uptake from the two measurement approaches differed. Both measurement techniques, however, determined that the ASP field had carbon uptake consistent with the amount required to meet goals in the “4 per mil” initiative, which aims to increase carbon storage in agricultural fields by 0.4% (4 per mil) per year to offset carbon emissions from burning fossil fuels. The EC measurements were continuous in time, which allowed us to determine that the cover crops, which were not harvested, were the primary cause of differences between the ASP and BAU fields. Results from this study illustrate the value of conservation practices in a changing climate and the value of eddy covariance measurements for assessing climate smart practices.

Technical Abstract: Climate smart agricultural practices have received considerable attention recently for their potential for climate change mitigation through sequestering atmospheric carbon. Despite the enthusiasm for climate smart practices, there is limited evidence they are more effective at removing carbon from the atmosphere and storing it in the soil than current practices. We hypothesized that a field with aspirational (ASP) practices (i.e., no-till corn-soybean-wheat-hay rotation with cover crops) would accumulate more soil organic carbon (SOC) versus a business-as-usual (BAU) field (i.e., conventional-tillage, corn-soybean-soybean rotation). We used deep soil cores (1 m) to assess changes in soil organic carbon (deltaSOC) between 2016 and 2022 for the two fields and compare with estimates based on eddy covariance calculation of deltaSOC. We found that the ASP field had carbon uptake that was positive, and larger than the BAU field. Both the soil sample method (deltaSOCSS) and the eddy covariance method (deltaSOCEC) agreed on this point, but the magnitude of carbon uptake was much larger when estimated with soil samples (deltaSOCSS was 1.9 ± 1.7 % yr-1 and -0.7 ± 1.3 % yr-1 at ASP and BAU, respectively) than with eddy covariance (deltaSOCEC was 0.33 ± 0.09 % yr-1 and 0.12 ± 0.06 % yr-1 at ASP and BAU, respectively). Finally, we used the continuous measurements of carbon fluxes from the eddy covariance towers to evaluate which conservation practice (cover crops, no-till, or expanded crop rotation) led to the most carbon uptake. We found that cover crops, that were not harvested, were the primary cause for the difference in deltaSOC between the ASP and BAU fields. The cover crops prevent carbon losses that otherwise occur when the field is fallow. Results from this study illustrate the value of conservation practices in a changing climate and the value of eddy covariance measurements for assessing climate smart practices.