An academic review article that looked at 144 previous studies of the benefits of no-till agriculture has raised doubts about whether no-till really sequesters carbon to the extent that has been suggested.
The study, published by Geoderma, is titled “Declines in soil carbon storage under no tillage can be alleviated in the long run.” It re-examined 1,061 pairs of published experimental data sets in previous studies comparing no-till and conventionally tilled soils. In particular, the study looked at carbon storage in the upper 10 centimeters of topsoil, where most studies measure carbon, vs. carbon in lower depths. It found that these [no-till]-driven [soil organic carbon] losses diminished over time and the net change was approaching zero at 14 years.”
It concluded, “Our findings demonstrate that NT is not a simple guaranteed solution for drawing down atmospheric CO2 and regenerating the lost SOC in cropping soils globally and highlight the importance of long-term NT for the recovery of initial SOC losses.”
The study’s authors speculated about their findings, wondering whether soil compaction over time prevents carbon movement to lower depths.
The study did not address other known benefits of no-till, such as water and soil retention. It suggested that soil carbon estimates found in reports by the Intergovernmental Panel on Climate Change may have to be recalibrated.
David Murray can be reached at [email protected].
