A soon-to-be published manuscript in the Journal of Geophysical Research—Biogeosciences could very well set the tone for the modeling of carbon budgets in agricultural areas.
Led by Thanos Papanicolaou, the Goodrich Chair of Excellence in the University of Tennessee, Knoxville, Department of Civil and Environmental Engineering, it found that carbon budgets in agricultural areas still fall short when compared to similar budgets for grasslands or forests due to the complexities introduced by humans.
Co-authored by Papanicolaou, his PhD students, Ken Wacha and Ben Abban, CEE research faculty Christopher Wilson, USDA-ARS National Lab for Agriculture and Environment director Jerry Hatfield, Charlie Stanier of the University of Iowa, and Tim Filley of Purdue University, the study adds a new component that captures the transport of light soils that are enriched in organic matter along a hillslope, which most current models neglect.
“This manuscript presents novel work that merges a watershed erosion model with an organic matter cycling model and builds new functionality allowing simulation of the transport of light organic matter along a topographic gradient,” said Papanicolaou. “The model is applied to twentieth-century changes in soil carbon across a farmed hillslope and compared with recent soil carbon data. The chronosequence in SOC storage for the erosional zone revealed that conservation tillage and enhanced crop yields begun in 1980s reversed the downward trend in SOC losses, causing nearly 26 percent of the lost SOC to be regained.”
Papanicolaou and team used the model supplemented with collected soil sample data to track modern day (since 1930) changes of soil carbon and soil health in a farm field under different management practices.
“We set out not to go over data that had already been collected, but to make new findings,” said Papanicolaou. “We wanted to understand what happened to carbon levels over time, and hopefully develop some new directions for soil use out of that.”
The team began with the theory that the typical method for measuring soil health—taking periodic soil cores—wasn’t as effective as thought because it didn’t account for variations in properties like soil type and slope across the landscape, or for changes in land management.
This study allowed the team to see how soils degraded due to the combination human activity and climate.
What they found was that carbon storage levels varied greatly from accepted norms. The team showed that the soils were continually depleted of the rich organic matter long after the end of the “Dust Bowl” era due to the enhanced erosion that accompanied our agricultural practices.
The levels of organic matter in the soil hit bottom in the late 1980s, right before new Congressional farm bills went into effect, but things are turning around.
“Our study brought together hydrology, biology, geochemistry, engineering and mathematics in a way not previously done,” said Papanicolaou. “We were able to show that yes, soils are improving, but the methods of farming from 1935-1987 have taken their toll.”
The realization that the organic matter in the soil, and in some sense, its overall soil health has improved to almost half its level in the 1930s was an exciting find, one that is an example of the program that made the study possible.
This works stems from a partnership co-led by Thanos Papanicolaou and Professor Praveen Kumar from the University of Illinois, the lead institution, and includes an interdisciplinary mix of scientists and engineers from the University of Iowa, Indiana University, Purdue University, Northwestern University, the University of Minnesota, Penn State University and Utah State University, in addition to UT and Illinois.
This team has formed the Intensively Managed Landscapes Critical Zone Observatory, one of only 10 observatories in the US supported by the National Science Foundation to monitor the key processes at work between the bedrock and the top of the canopy.
The goal of the CZOs is to synthesize this information into a unifying theoretical framework that integrates new understanding of coupled hydrological, geochemical, geomorphological, sedimentological and biological processes.
“Their mission is to push the envelope of science and engineering,” said Papanicolaou. “We’re engineers developing science products to aid in that goal.”
The IML-CZO is unique in that it is the only CZO to focus entirely on human modified areas. Papanicolaou said that the research and breakthroughs being done through the IML will take time, but that these early findings are a sign of what’s to come and what can be done to improve soil quality. The outcomes of IML could soon change farming and conservation techniques around the world.
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C O N T A C T :
David Goddard (865-974-0683, david.goddard@utk.edu)