Responses of soil greenhouse gas emissions to no-tillage: A global meta-analysis

No-tillage (NT) is an effective agricultural practice for climate change mitigation and food security, which is extensively adopted worldwide. The sustainability of NT depends on the trade-offs between NT-induced crop productivity and greenhouse gas (GHG, i.e., CO2, CH4, and N2O) emissions. The climate and soil properties strongly influence the trade-offs and contradictory observations have been made by different researchers. To evaluate the responses of crop yields and GHG emissions to NT in various cereal systems, a global meta-analysis of 946 paired data from 116 peer-reviewed studies was conducted in this work. Overall, NT reduced global warming potential (GWP) by 14.4 % but did not change crop yields. Specifically, NT significantly inhibited CO2, CH4, and N2O emissions and enhanced CH4 uptake in temperate zones, with GWP decreased by 12.3 % in subtropical zones only. The clay loam and silt loam were recommended for NT practice implementation globally. Further analysis suggested that NT reduced GWP by 10.8 % in barley, 13.7 % in maize, 22.5 % in rice, and 30.1 % in soybean. NT dramatically increased wheat and soybean yields globally, whereas reduced barley yields significantly, indicating cautious consideration should be taken for NT implementation in barley fields. The suppression effect in GHG emissions and GWP could be reduced under long-term (>10 years) NT practices, which, on the other hand, improved crop yields by 5.57 %. NT inhibited emissions of the three GHGs in acid and alkaline soils, and hindered CH4 uptake strongly in neutral soils. This meta-analysis offers a solid scientific foundation for assessing the effects of NT practices on GHG emissions and agricultural productivity. It also offers fundamental knowledge for mitigating climate change by NT.