Soil is the largest terrestrial carbon sink on the planet. The top meter of global soils contains approximately 2,500 gigatons of carbon, more than three times the amount in the atmosphere and roughly four times the amount stored in all living vegetation. Yet soil carbon is declining in many agricultural and urban landscapes due to practices that disrupt soil structure, reduce organic matter inputs, and accelerate decomposition.
For the past three years, TerraFuture's research team has been conducting a systematic study of soil carbon dynamics across 46 sites in the Willamette Valley, comparing conventional land management practices with regenerative approaches. The results, now published in the journal Soil Biology and Biochemistry, demonstrate that soil represents an underutilized and highly scalable carbon sequestration opportunity.
Study Design
Our study sites span four land use categories: conventional agriculture with tillage, no-till agriculture, managed urban green spaces including parks and community gardens, and restored native prairie. At each site, we collected soil cores at depths of 0 to 15 centimeters, 15 to 30 centimeters, and 30 to 100 centimeters at the beginning of the study and annually thereafter. Samples were analyzed for total organic carbon, microbial biomass carbon, aggregate stability, and bulk density.
We also installed continuous soil moisture and temperature sensors at 28 sites to model the relationship between environmental conditions and carbon flux.
Key Findings
The results demonstrate clear and consistent differences in soil carbon trajectories across management types.
Sites under regenerative management, characterized by no-till practices, cover cropping, diverse rotations, and compost application, gained an average of 1.8 metric tons of carbon per hectare per year in the top 30 centimeters. The range across sites was 1.1 to 2.8 metric tons, with variation driven primarily by soil texture, initial carbon content, and the specific suite of practices employed.
Conventionally tilled agricultural sites lost an average of 0.6 metric tons of carbon per hectare per year, consistent with established literature on tillage-driven carbon loss. No-till sites without additional regenerative practices showed modest gains of 0.3 metric tons per hectare per year.
Restored native prairies, managed with periodic prescribed fire, showed the highest per-hectare carbon gains at 2.4 metric tons per year, driven by the deep root systems of native perennial grasses and the positive effects of fire on microbial community composition.
Soil is not just a medium for growing food. It is an active carbon management system, and the data shows that management decisions directly determine whether soil functions as a carbon source or a carbon sink.
The Microbial Connection
Perhaps the most scientifically interesting finding relates to soil microbial communities. Using 16S rRNA gene sequencing, we characterized bacterial and fungal communities across all 46 sites. Regenerative sites showed 43 percent greater microbial diversity than conventional sites, with a particularly notable increase in mycorrhizal fungi, the symbiotic organisms that facilitate carbon transfer from plant roots to stable soil organic matter.
Sites with the highest mycorrhizal fungi abundance showed carbon sequestration rates 1.6 times greater than sites with low fungal diversity, even after controlling for management practices and soil type. This suggests that the microbial community is not just an indicator of soil health but an active driver of carbon sequestration potential.
Scaling Implications
The Willamette Valley contains approximately 450,000 acres of agricultural land. If regenerative practices were adopted on just 30 percent of that acreage, our data suggests an additional 243,000 metric tons of CO2 equivalent could be sequestered annually. That represents approximately 4.2 percent of Oregon's total annual greenhouse gas emissions.
Combined with urban soil management improvements in Portland's 12,600 acres of parks and green spaces, the total potential rises to approximately 270,000 metric tons per year.
What Comes Next
TerraFuture is using these findings to advocate for state-level incentive programs that compensate land managers for verified soil carbon gains. We are also expanding our soil monitoring network to 80 sites and partnering with Oregon State University Extension to develop practical guidance for farmers transitioning to regenerative practices.
The ground beneath us has been overlooked for too long. The data shows it deserves to be at the center of our climate strategy.
