Researchers have demonstrated a series of biological tests that could serve as “proxies” for measuring how different regenerative agriculture practices could improve soil carbon – years before it would be possible to measure the carbon directly. The technique offers new insights into how effective various regenerative practices are at improving soil health.
The phenomenon is explored in a new study from North Carolina State University in collaboration with North Carolina A&T State University and Emory University, which stacked multiple regenerative practices on top of each other and then measured biological parameters including enzyme activity, microbial biomass (living microbes) and microbial necromass (dead microbes). All of those parameters serve as proxies for the amount of carbon stored in soil.
Soil carbon is a cornerstone of soil health, supporting nutrient cycling, biological activity, soil structure and long-term functioning of soil ecosystems. Biomass and necromass serve as early markers of soil carbon formation and loss and can be measured years before traditional soil carbon measurements may become detectable.
“When microbes in the soil consume carbon, they release enzymes to break that carbon down; then they consume some of it,” said Debjani Sihi, corresponding author of a paper on the work and an assistant professor of plant and microbial biology and crop and soil sciences at NC State. “After that, the microbes respire some of the carbon, meaning they spit it back out into the atmosphere. While doing this, they are also building their biomass and necromass when they die.”
Microbial necromass stores soil carbon effectively over the long term, Sihi said, because necromass carbon can more easily create strong chemical bonds with minerals in the soil. This leads to the creation of a carbon “reservoir,” which can help indicate soil health and carbon storage capacity.
Researchers layered regenerative practices including differing levels of tillage (the mechanical preparation of soil for agriculture) and a series of different cover crop mixes onto existing loblolly pine and pecan agroforestry systems on the NC A&T research farm.
Differences were observed between the pecan and pine systems – pecan trees showed higher total biomass and influenced soil microbial respiration differently, because their broadleaf foliage is more easily degraded by microbes compared to loblolly pine needles.
Enzyme activities also responded to tree species and cover crop treatments, showing that these biological proxies can provide early insights into changes in soil nutrient cycling. No significant carbon differences were found between minimum and no tillage approaches, which Sihi said was a point in favor of continuing with minimum tillage practices since they confer other benefits like reducing weed pressure without hindering carbon buildup.
These findings show that microbial biomass and necromass can be effective early indicators of soil health, offering scientists a powerful tool for approximating soil carbon storage years ahead of when they could normally measure it.
The paper, “Soil Carbon Cycle Proxies in a Regenerative Land Management System” is published in the Journal of Natural Resources and Agricultural Ecosystems. Co-authors include co-first author Murray Sternberg, K. Taylor Cyle, Milon Barmon, Jack Kagan and Gwen Read of Emory University and co-first author Biswanath Dari, John Kimes, Randall Quillian and Manoj Kumar Reddy Sangireddy of NC Agricultural and Technical State University.
Funding support for this study comes from Valent BioSciences (a subsidiary of Sumitomo Chemical Co., Ltd.), USDA’s National Institute of Food and Agriculture Research Capacity Fund (HATCH, HATCH MULTISTATE, Grant/Award Numbers: 7009808, 7010251), the Emory University Department of Environmental Sciences Lester Research Grant, the USDA Renewable Resources Energy Act (Grant/Award Number: NI24RREAFXXXG024), the National Institute of Food and Agriculture Sustainable Bioeconomy Program (Grant/Award Number: 2023-68016-40133 (accession # 1029684), the Natural Resources Conservation Service (Grant/Award Number: NR243A750003C105), and Organic Transitions Program (ORG Grant/Award Number: 2024-51106-43042). This study was supported in part by the Emory HPLC Bioanalytical Core (EHBC), which is subsidized by the Emory University School of Medicine and is one of the Emory Integrated Core Facilities.
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