In the drylands of Eastern Oregon, wheat farming is a way of life — and growers are looking for ways to replenish stored soil carbon and improve soil health in their fields.
Oregon State University researchers at the Columbia Basin Agricultural Research Center (CBARC) outside of Pendleton conducted a study in which they analyzed how different farming practices affect soil carbon levels over a nearly 60-year period. Specifically, they looked at what happens when spring peas are added to the wheat rotation and when tillage is reduced or eliminated.
Building carbon-rich soils through legume-based crop rotations and no-till farming enhances soil health and water retention, leading to potentially higher yields for Oregon wheat farmers.
These methods — known as legume-based crop rotations and no-till farming — are conservation practices that protect soil structure, encourage biological activity, and leave more plant residue on the field to naturally rebuild carbon.
Using archived soil samples and advanced testing techniques, researchers measured how much carbon was stored in the top 30 centimeters of soil from 1963–2021. They compared fields using the traditional winter wheat summer fallow (WW-SF) system to those where wheat was rotated with spring peas, under both conventional tillage and no-till systems.
The results were clear: conservation practices worked. Farms that included spring peas in rotation added 0.15 to 0.16 tons of carbon per hectare each year — a modest but steady gain. In contrast, WW–SF systems lost carbon at a rate of 0.11 tons per hectare annually. In deeper soil layers, losses were even greater in traditional systems.
Notably, the no-till wheat–pea rotation stored 60% more carbon in the soil’s most stable form compared to the WW–SF system. This form, called mineral-associated organic matter (MAOM), breaks down slowly and serves as a long-term carbon reservoir — helping to stabilize soils and slow the release of carbon dioxide into the atmosphere.
While the study area covers less than 1% of Oregon’s croplands, if the same practices were adopted more broadly, they could offset around 0.20% of the state’s annual agricultural greenhouse gas emissions. More importantly, they offer real benefits to farmers, including improved soil health, better water retention and potentially higher yields.
This long-term study, published in the journal Scientific Reports and funded by the U.S. Department of Agriculture Agricultural Research Service, shows that even in dry, challenging environments, it's possible to rebuild soil carbon and make agriculture part of the climate solution. But to fully realize this potential, financial incentives and supportive policies are needed to reward farmers for the environmental services they provide.
The study was led by Paulina B. Ramírez, an OSU research associate at CBARC. Co-authors on the study include Francisco Calderón, soil scientist and CBARC director; Surendra Singh, assistant professor and director of Washington State University’s Lind Dryland Research Station; and Stephen Machado, OSU professor of crop physiology and agronomy at CBARC.
Building carbon-rich soils through legume-based crop rotations and no-till farming enhances soil health and water retention, leading to potentially higher yields for Oregon wheat farmers. These practices also reduce greenhouse gas emissions, benefiting the public by contributing to climate-friendly agriculture and promoting sustainable farming methods.