Scientists have shown that living and dead soil microbes can act as early indicators of soil carbon storage, providing farmers and researchers with a faster way to evaluate the impact of regenerative agriculture practices.
The study, led by researchers from North Carolina State University in collaboration with North Carolina A&T State University and Emory University, found that microbial biomass, microbial necromass and enzyme activity can serve as biological “proxies” for soil carbon, a key measure of soil health.
The findings are significant because changes in soil carbon often take years to become detectable through traditional testing methods. By contrast, microbial indicators can provide an earlier signal of whether management practices are improving the soil.
Testing stacked regenerative practices
Researchers evaluated the impact of combining multiple regenerative practices, including different tillage regimes and cover crop mixtures, within existing loblolly pine and pecan agroforestry systems at the NC A&T research farm.
The team measured enzyme activity, microbial biomass, representing living microbes, and microbial necromass, the carbon-rich remains of dead microbes. All three metrics are closely linked to the soil carbon cycle and can help estimate the soil’s capacity to store carbon.
“Soil carbon is a cornerstone of soil health,” said corresponding author Debjani Sihi, assistant professor of plant and microbial biology and crop and soil sciences at NC State. Healthy soil carbon levels support nutrient cycling, biological activity, soil structure and the long-term functioning of agricultural ecosystems.
Dead microbes play a key role
According to the researchers, microbial necromass may be particularly important as an indicator because it contributes to stable, long-term carbon storage.
“When microbes in the soil consume carbon, they release enzymes to break that carbon down and use part of it for growth,” Sihi explained. As microbes die, their remains can form strong chemical bonds with soil minerals, creating a relatively stable carbon reservoir.
This process makes necromass a useful marker for understanding both soil health and future carbon storage potential.
Different systems respond differently
The study also highlighted differences between agroforestry systems. Pecan-based systems supported greater total microbial biomass and influenced soil respiration differently from loblolly pine systems, largely because broadleaf pecan litter decomposes more readily than pine needles.
Enzyme activity also varied according to tree species and cover crop treatments, suggesting that biological proxies can offer insights into changes in nutrient cycling as regenerative practices are adopted.
Notably, researchers found no significant differences in carbon-related indicators between minimum-tillage and no-tillage treatments. Sihi said this supports the continued use of minimum tillage, which can provide additional benefits such as weed suppression without compromising soil carbon accumulation.
Implications for regenerative agriculture
The researchers believe the approach could help overcome one of the biggest challenges facing regenerative agriculture projects: demonstrating measurable improvements in soil health within practical timeframes.
By using microbial biomass and necromass as early indicators, scientists may be able to estimate changes in soil carbon storage years before those changes become detectable through conventional soil carbon measurements. This could allow farmers, researchers and sustainability programmes to assess the effectiveness of regenerative practices more quickly and refine management strategies accordingly.
The study, Soil Carbon Cycle Proxies in a Regenerative Land Management System, is published in the Journal of Natural Resources and Agricultural Ecosystems.
