A fascinating technical article from No-Till Farmer on measuring soil organic carbon in soil managed under different tillage regimes.
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 [new] 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," Olson said.
The comparison method assumes the conventional tillage baseline to be at a steady state and having the same amount of SOC at the beginning and at the end of the long-term study, and this may not be true. No-till as the experiment treatment needs to be compared to itself on the same soils over time to determine if SOC sequestration has really occurred.
