College of Agriculture & Natural Resources Department of Plant, Soil and Microbial Sciences

A new study by researchers at Michigan State University’s College of Agriculture and Natural Resources (CANR) explores the long-term impact of conservation management practices on soil organic carbon (SOC) content.  

The 25-year study, “Soil carbon change in intensive agriculture after 25 years of conservation management,” was conducted at the MSU Kellogg Biological Station (KBS) and explores best practices for building soil carbon through differing management strategies.  

Key researchers in the study include G. Philip Robertson, Ph. D., a University Distinguished Professor, and Alexandra Kravchenko, Ph. D., a professor, both in the Department of Plant, Soil and Microbial Sciences. Carolina Córdova, Ph. D., is the study's lead author and is now an assistant professor at the University of Nebraska-Lincoln, and co-author Jessica Miesel, Ph. D., is now an associate professor at the University of Idaho. 

Soil organic carbon: A foundation of soil health 

Soil gains carbon through a process known as carbon sequestration, whereby plants absorb carbon dioxide from the atmosphere during photosynthesis. Plants release carbon into soil through their roots and as they decompose, where microorganisms transform it either to CO2 that is then emitted to the atmosphere or into stable forms of carbon that persist in soil.  

Building and retaining soil organic matter is vital for agricultural productivity. SOC is the primary constituent of soil organic matter, which is a major source of nutrients for plants and contributes to the soil’s structure and stability. Increased SOC levels are linked to numerous agricultural benefits, including improved soil fertility and better resilience to environmental stressors. SOC also supports nutrient cycling, boosts weed control and protects against pathogens.  

Additionally, when plants pull carbon dioxide out of the air, they reduce its concentration in the atmosphere, helping to remove greenhouse gases and limit rises in global temperature.  

“The single best predictor of soil health is soil organic carbon content,” said Robertson. "It affects everything from a soil’s water-holding capacity to its nutrient supply capacity and crop productivity. Soil carbon is a foundational feature of agricultural systems, and often their success depends on SOC levels.” 

But despite its importance, SOC has been severely depleted in many regions. It’s estimated that cropping systems in the U.S. Midwest have lost 40 to 60 percent of their initial SOC since European settlement, primarily due to land conversion and conventional agricultural practices. This decline has had significant consequences, including diminished soil fertility and increased erosion rates.  

The win-win benefits of improving soil health 

To address these issues and better understand the impact of land management practices on SOC levels, the authors observed SOC change across 10 replicated ecosystems. These included annual row crop rotations, managed perennial crops and conservation lands. Researchers collected samples to assess the long-term effects of each system, offering valuable insights into how land management can help mitigate SOC loss and improve soil health over time. 

“If we can utilize agricultural management and land use practices to stop losses of soil organic matter or increase soil organic matter, it’s a win-win situation,” said Kravchenko. “We can increase soil fertility and yield. We can help improve the characteristics of soil structure and help it hold more water. We can take more carbon out of the atmosphere. It’s a win-win whichever way you look at it.” 

The study’s 25-year duration was instrumental in understanding gradual changes in SOC, as year-to-year changes are often too small to quantify accurately. This long-term perspective provides valuable insights into the lasting benefits of sustainable land management practices. 

“It can take several years to see some of the benefits of these practices, both physically and economically,” said Robertson. “For example, it took about 13 years for the no-till system at KBS to show a consistent yield increase over the conventional tiallage approach. And now it's quite striking. There is a clear economic benefit from no-till available to persistent farmers.” 

The study found notable differences in SOC stocks across various cropping systems. While conventionally managed row crop and late successional forest systems showed stable SOC levels, no-till, cover crops and managed herbaceous perennials showed SOC increases. The highest gains were seen in managed perennial and cover-cropped systems suggesting that systems with minimal disturbance and cover crops may lead to more stable, long-term gains in SOC.  

Interestingly, the buildup of SOC slowed after the first 12 years, with most changes occurring in the surface layers. Deeper layers showed less significant changes. 

The need for long-term investment in soil health 

The study's findings have significant implications for sustainable agriculture. They offer valuable insights for farmers and policymakers looking to adopt agricultural practices that can improve soil health and support environmental resilience. 

“This knowledge provides powerful tools for combating environmental change,” said Robertson. “This work will help us enhance crop resilience to variability in weather and other growing conditions, a critical component of soil health. It directly affects farmers’ success adapting to an increasingly unpredictable climate.” 

Looking ahead, Robertson and Kravchenko hope to see a commitment to and widespread recognition of the importance of SOC sequestration.  

“The lessons here regarding the importance of these conservational practices like no-till and cover crops are important,” said Kravchenko. “These practices make a real difference. We must stick to them to see the numerous benefits come to light.” 

“Society must make a long-term investment in soil health. It's not a benefit just for the farmer. It's a benefit for society in general. Healthy soils lead to better environmental outcomes and enhanced food security,” said Robertson. “And we need to remove carbon dioxide from the atmosphere if we want to return to a more stable climate. Various technologies have been proposed to do this, but they're costly and not yet proven. On the other hand, photosynthesis is available today at relatively low cost. We should take advantage.”