URBANA Increased levels of greenhouse gases, particularly carbon dioxide (CO2), have been associated with the burning of fossil fuels, deforestation, cultivation of grasslands, drainage of the land, and land use changes. Concerns about long-term shifts in climate patterns have led scientists to measure soil organic carbon (SOC) in agricultural landscapes and to develop methods to evaluate how changes in tillage practices affect atmospheric carbon sequestration. University of Illinois professor of soil science Kenneth Olson has used data collected over a 20-year period at Dixon Springs, Ill., to develop a new protocol for more accurately measuring the carbon removed from the atmosphere and subsequently sequestered in the soil as SOC.
"Many experiments comparing no-till to conventional tillage on similar soils have shown no-till to have higher levels of soil organic carbon," Olson said. "So we know in general that no-till is often better than conventional tillage at building or retaining more of the organic matter in the soil, which is important to crop productivity. However, this does not mean that no-till is necessarily sequestering atmospheric carbon. It is often just losing carbon at a lower rate than conventional tillage." This unexpected discovery was the result of Olson's use of a pre-treatment SOC measurement method that compares change in soil organic carbon over time on the same plots using the same tillage methods. "This protocol does not assume that soil carbon pools are at steady state (remain the same over time), but measures SOC at the beginning of an experiment, at intervals during, and at the end of the experiment," Olson said.
"Comparison studies with one treatment as the baseline (usually conventional tillage) or control and other tillage such as no-till as the experimental treatment should not be used to determine SOC sequestration if soil samples are only collected and tested once during or at the end of the study," Ol
|Contact: Debra Levey Larson|
University of Illinois College of Agricultural, Consumer and Environmental Sciences