Leopold Center for Sustainable Agriculture

Carbon cycling research fills gaps in knowledge

Back to Leopold Letter Fall 2012

By MELISSA LAMBERTON, Leopold Center graduate research assistant

The Midwest’s famous organic-rich soils have enormous potential to store carbon, protect cropland fertility and reduce the amount of carbon dioxide delivered to the atmosphere. Yet scientists still want to know more about how farming practices influence carbon movement.

A multidisciplinary project funded by NASA’s Experimental Program to Stimulate Competitive Research (EPSCoR) seeks to fill that gap in knowledge. The project will develop models to quantify how carbon moves through a typical Midwestern midsize watershed in Iowa, with global implications in mind. The Leopold Center contributed special grant funding for a portion of the project.

“The U.S. Midwest due to its clay-rich soil has the greatest potential to sequester carbon—as long as the appropriate management practices are followed,” said Thanos Papanicolaou of the University of Iowa’s IIHR-Hydroscience & Engineering and Department of Civil and Environmental Engineering, the principal investigator for the project.

“We have a great opportunity here in the state and beyond to contribute not just to food production but also to carbon storage as well as other environmental services,” Papanicolaou said.

Previous studies have estimated that conservation practices on farmland can keep nearly 33 megatons of carbon in the soil every year. But these studies have treated the landscape as a static ecosystem, rather than a dynamic one, and often fail to properly account for interplays between human activities and nature. Questions remain about how crop respiration, soil respiration, and tillage-induced soil erosion and deposition contribute to carbon losses and gains to the atmosphere or local waterways.

Papanicolaou’s team uses experimental plots in the Clear Creek watershed in eastern Iowa to explore the relationship between carbon and land management practices. The plots, 5 by 15 feet, mimic conventional corn-soybean agriculture, Conservation Reserve Program grass, and various management practices such as no-till and tilling at different times of the year. Researchers and students monitor each plot, measuring parameters such as crop height, crop yield, leaf litter, weather-related data and soil characteristics, as well as soil organic matter and carbon dioxide.   

The Clear Creek data are utilized in two commonly used numerical models, WEPP and CENTURY. WEPP, which stands for the Water Erosion Prediction Project, models soil erosion rates under different scenarios, taking into account topography, soil characteristics, land management practices and climate. The researchers can look at single storm events or model the next 50 or 100 years. These results go into the CENTURY model, which predicts the redistribution of carbon in the watershed.

To validate the results, researchers compare the data from the coupled models with on-the-ground measurements collected from different locations in the Clear Creek watershed.  

Together the models show the patterns of carbon loss due to soil movement in a typical corn-soybean system at the landscape scale and over long periods of time. The research will lead to suggested scenarios for mitigating carbon loss. Other researchers have applied similar modeling work to forests and grasslands, but little attention has been paid to agricultural fields. The researchers hope these models will help lead to sound policy decisions about land management.  

“We need to maintain carbon in the soils if we really are striving toward a sustainable environment,” Papanicolaou said.   

The Leopold Center has two new On the Ground videos about this project.

The project team includes collaborators from the University of Iowa, University of Northern Iowa, Iowa State University, U.S. Department of Agriculture and NASA. Investigators include University of Iowa Ph.D. students Ken Wacha and Ben Abban, and Dimitrios Dermisis, a former Iowa student and currently a faculty member at McNeese State University.

Back to Leopold Letter Fall 2012