Anthropogenic and inherent effects on soil organic carbon across the U.S.

Authors: NUNES, MARCIO - Orise Fellow; VAN ES, HAROLD - Cornell University; Veum, Kristen; AMSILI, JOSEPH - Cornell University; Karlen, Douglas

Submitted to: Sustainability
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2020
Publication Date: 7/15/2020
Citation: Nunes, M., Van Es, H., Veum, K.S., Amsili, J., Karlen, D.L. 2020. Anthropogenic and inherent effects on soil organic carbon across the U.S. Sustainability. 12(14). Article 5695. https://doi.org/10.3390/su12145695.
DOI: https://doi.org/10.3390/su12145695

Interpretive Summary: Soil organic carbon (SOC) is a keystone soil health indicator, but interpretation of land management-induced changes in SOC requires an understanding of site-specific characteristics such as soil type and climate, otherwise known as inherent factors. This large-scale study with 7610 observations from across the U.S. evaluated the effects of several agronomic management practices as well as important inherent factors, including precipitation, temperature, and soil texture, on SOC content in topsoil. Results of this study demonstrated that SOC content increased with reduced tillage and residue removal, and increased with cover crops, manure, and cropping system diversification. In addition, SOC content increased with precipitation and decreased with temperature, and was greater in fine-textured versus coarse-textured soils. This study benefits landowners, producers, and advisors by demonstrating the influence of site-specific characteristics on SOC content, and provides information for improved land management decisions in support of more sustainable and resilient agricultural systems.

Technical Abstract: Soil organic carbon (SOC) has a major role in several soil functions and is recognized as the most significant single soil health indicator. Understanding anthropogenic and inherent effects on SOC is crucial to improve SOC management and interpretation. The response of topsoil (< 15 cm) SOC to tillage depth and intensity, cover crop, stover removal, manure addition, and several agroecosystems was assessed based on 7610 observations across eight regions of the United States (U.S.). Overall, reducing depth and intensity of tillage and including cover crops into the cropping system increased SOC. The positive effect of cover crop was more noticeable in South Central, Northwest, and Midwest U.S. regions. Removing crop residues decreased SOC in the Midwestern and Southeastern soils, but only when it was removed at high rates (>65%). Addition of manure increased SOC by 21 to 41%, relative to unmanured soils, depending on the U.S. region. Moreover, more diversified agroecosystems (i.e., small mixed vegetables, perennial, and dairy crop systems) had the highest topsoil SOC content, while more intensive systems, such as annual row crops and large-scale single vegetable production systems, had the lowest. Analysis of inherent factors indicated that SOC increased with precipitation and decreased with temperature across the U.S., with arid and more humid regions having the lowest and highest SOC content, respectively. Further, fine-textured soils demonstrated higher SOC content than coarse-textured soils. This nationwide assessment confirmed the benefits of conservation practices for improving topsoil SOC in the continental U.S. and highlighted the sensitivity of this soil health indicator to inherent factors.