Much of the research data over the past 20 years has suggested that switching from conventional tillage to no-till can sequester more soil-organic carbon. Yet there’s a growing concern among scientists that no-tilling corn and soybeans without cover crops, small grains and forages in the rotation may not be increasing soil organic-carbon stocks to earlier predicted levels.

“Some studies have shown both moldboard and no-till systems are actually losing soil organic-carbon over time,” says University of Illinois soil scientist Ken Olson, who led a carbon sequestration review conducted by university researchers in four Corn Belt states. They looked at 120 published soil science and tillage research papers related to soil organic-carbon sequestration, storage, retention and loss.

No-Till Benefits

Olson says no-till systems on sloping and eroding sites retain more soil-organic carbon in the top 6 inches when compared to moldboard plowing. This is due to less soil disturbance, reduced soil erosion and decreased movement of soil organic-carbon-rich sediment off the plots.

However, Olson says the no-till subsurface layers also need to be sampled and tested to the depth of rooting, or roughly 3 to 6 feet, because the no-till subsurface layer is often losing more soil organic-carbon over time than is gained from the surface layer.

During the extensive analysis, Olson says it became apparent that there were a number of reasons for the conflicting findings. The team cited dozens of factors that need to be considered and projected it would require a highly impractical a 20- to 50-year-long study…