Scientists have discovered that a ‘measure and remeasure’ technique is an effective method for verifying soil carbon storage in agricultural lands, contributing to climate change mitigation efforts.
According to a study co-authored by researchers from Yale School of the Environment, measuring soil carbon directly is more reliable than relying on predictive models. This allows for accurate assessments of carbon storage, enhancing confidence in carbon markets for crop production, as detailed in a recent publication in Environmental Research Letters.
The study revealed that utilizing proper research designs suited for the agricultural scale can effectively verify the amount of carbon sequestered in soil through climate-smart practices. These practices include growing cover crops and minimizing soil disturbance through reduced tillage. The research team noted that direct measurements, combined with conventional study designs from fields like epidemiology, can also quantify the impact of these practices on soil health and other important factors.
Mark Bradford, co-author of the study and the E.H. Harriman Professor of Soils and Ecosystem Ecology, mentioned, “Our findings indicate that we can perform direct measurements on a larger scale, extending its use beyond carbon markets to other greenhouse gas accounting efforts, such as national emissions reporting by countries.” Bradford contributed to this research through the Yale Applied Science Synthesis Program, part of the Yale Center for Natural Carbon Capture and The Forest School at YSE.
Natural carbon solutions, such as managing agricultural lands to boost carbon storage, are deemed crucial by the Intergovernmental Panel on Climate Change (IPCC) in addressing the challenges posed by climate change. Bradford highlighted that soil organic carbon (SOC) accounting and crediting typically employs measure-and-model methods, which depend on predictive biogeochemical models driven by small-scale trials and limited direct measurements. However, these models’ accuracy in real agricultural settings remains uncertain. The researchers advocate for a “measure and remeasure” strategy that uses soil samples collected from hundreds of fields for reliable evidence of carbon storage.
Bradford pointed out that accurately tracking soil carbon changes is complicated since these changes occur slowly against a significant background stock, necessitating the collection and analysis of numerous samples. This method, traditionally seen as too expensive at smaller scales, can be more feasible when applied broadly.
The team found that by sampling 10% of fields across numerous farms—potentially spanning tens of thousands of acres—over extended periods, they could gather trustworthy data. Employing direct measurement and remeasurement of soil carbon, using rigorous study designs, results in carbon credits that more accurately represent actual carbon storage. This helps buyers ensure that their investments support genuine climate benefits while reducing costs as projects expand. The method could also validate the efficacy of predictive models used in other forms of greenhouse gas accounting on croplands, such as the internal assessments companies conduct to achieve their net-zero targets.
To assist farmers in evaluating the cost-effectiveness of soil management projects, Eric Potash, a research scientist with the Agroecosystem Sustainability Center (ASC) at the University of Illinois and the study’s lead researcher, created an open-source web application. This tool enables users to analyze the expenses and profitability of soil carbon initiatives based on specific factors, including project size, duration, analysis costs, and sampling strategies.
Bradford stated, “This research indicates that it may be possible to reliably assess how much soil carbon changes result from adopting climate-smart and regenerative agricultural practices. Addressing measurement and verification concerns regarding soil carbon stocks will facilitate prioritizing policies and investments aimed at soil restoration and conservation, leading to improved water and nutrient retention, soil aeration, and biodiversity. Healthy soils like these will be more resilient to extreme weather and enhance food security.”
The study was also co-authored by Emily Oldfield ’05, ’11 MESc, ’19 PhD, a soil scientist at the Environmental Defense Fund, and Kaiyu Guan, director of the ASC.
