Tillage (using mechanical methods to turn soil prior to planting) is a common practice that has a number of benefits for agriculture. However, it has been blamed for loss of carbon (C) from agricultural soils.

Rusting tractors at sunset, Perkins, OK. Photo: George Thomas / Flickr

Less-intensive tillage and no-tillage agriculture have been promoted as ways to mitigate negative impacts from tillage on soil quality and to preserve soil organic carbon (SOC). However, reviews and meta-analyses to date have given varying pictures of the effects of less-intensive tillage.

This systematic review synthesized a large body of evidence to answer the question: What is the impact of reduced tillage intensity on SOC?

It confirmed earlier findings that no-tillage and intermediate-intensity tillage increase SOC in upper soil levels compared to high-intensity tillage. However, although the results show an increase in soil carbon in the upper layers, this is not reflected in deeper soil layers, which is a problem for long-term carbon storage and for climate mitigation strategies that incorporate reduced tillage intensity.

The effect of tillage practices on total SOC stocks will be further evaluated in a forthcoming project, accounting for soil bulk densities and crop yields.