No-till increases soil denitrification via its positive effects on the activity and abundance of the denitrifying community

Shifting from conventional tillage to a no-till system can contribute to improving soil carbon sequestration and sustaining crop productivity. However, our understanding of the soil nitrogen (N) process through insights into the no-till effect on soil denitrification remains elusive. Here, we compiled data from 323 observations in 57 studies and quantified the responses of soil denitrification and the size and activity of the denitrifying community to no-till vs. conventional tillage. Across all studies, no-till significantly increased soil denitrification (85%) compared to conventional tillage. The no-till effect on soil denitrification was significantly dependent upon N fertilizer management, with a greater increase with N fertilization than without (101 vs. 46%). The increased soil denitrification under no-till was attributed to increases in the size and activity of the denitrifying community. On average, the potential denitrification activity, the total number of denitrifiers, and the abundance of denitrifying genes were increased by 66, 116, and 14–70%, respectively, in response to no-till. Our results demonstrate that soil denitrification under no-till leads to increased soil nitrous oxide (N2O) emission. This is supported by a larger response of soil N2O emission compared to the total denitrification, together with a significant increase (33%) in the (nirK + nirS)/nosZ ratio under no-till conditions. Therefore, the increased soil denitrification under no-till conditions may have negative impacts on soil N cycling and mitigation of N2O emission. •The effect of no-till on soil denitrification was meta-analyzed.•No-till significantly increased soil denitrification and N2O emissions.•No-till enhanced the activity and abundance of the soil denitrifying community.•An overall positive response of (nirK + nirS)/nosZ to no-till was found.