Doug Peterson, State Soil Health Conservationist with USDA, displays soil sample from a field that uses cover crops.
Credit: Kyle Spradley, MU College of Agriculture, Food & Natural Resources
There’s widespread consensus that climate smart agricultural practices like cover cropping, reduced and no-tillage and crop diversification can help farmers adapt to climate change and help reduce greenhouse gas emissions. Yet confidence in the impacts of these practices as a climate solution has been undermined by reliance on models to determine how much carbon has been accrued or retained in soils.
Soil organic carbon accounting and crediting relies on models because of the belief that direct measurement is too costly and cannot provide a practical solution to any large-scale measurement, monitoring, reporting and verification (MMRV) program for tracking soil carbon outcomes.
But that assumption may be wrong. Working with a team of researchers from the University of Illinois and Yale School of the Environment, Environmental Defense Fund found that a rigorous approach to soil carbon quantification that relies on taking soil samples before and after practice adoption across a large number of farm fields is economically feasible.
An affordable option for large-scale projects
In a new study, “Measure-and-remeasure as an economically feasible approach to crediting soil organic carbon at scale” published in Environmental Research Letters, the team explored how prices for soil sampling and analysis, costs related to adoption of new practices and prices for carbon credits influence the economics of measure-and-remeasure projects.
Larger projects — on the order of 1000 farm fields — with only about 10% of the fields measured for changes in soil carbon, can yield a competitive return on investment in five years if soil carbon accrues at rates similar to those from experimental research plots.
This measure-remeasure approach can provide validation that efforts aiming to increase soil carbon are having their intended impact — a necessary and important step to build confidence in these practices as a climate solution.
The team also developed a web app, where users can plug in variables related to the number and size of fields and the cost of soil sampling and lab analysis to determine how many soil samples are needed to optimize accuracy of soil carbon outcomes with economic feasibility of measure-remeasure campaigns.
This kind of validation will be especially helpful in clarifying expectations of the growing number of federal and private investments that encourage farmers to adopt these climate-friendly practices.