A switch to no- or reduced- tillage agriculture has been proposed as a way to mitigate climate change, by increasing the retention of carbon in the soil (soil organic carbon; SOC). These proposals suggest that reduced tillage intensity would allow carbon to build up over time without turning the soil over. This study, using a more precise means of estimating the amount of carbon held throughout the soil, confirms that this is true in the top layers of soil.

A tilled field in Snyder County, PA. Photo: Nicholas A. Tonelli / Flickr.

However, it also suggests that traditional ways of estimating carbon stocks are overestimating the amount of carbon being stored in total. The assumption that SOC will also increase significantly below the topsoil may be ill-founded. This study confirms the finding of an earlier systematic review that the benefits of switching from high-intensity tillage to no- or reduced-tillage agriculture are limited to the top 30 cm of soil. Below that, the change in carbon retention is negligible.