No tillage decreases GHG emissions with no crop yield tradeoff at the global scale

Abstract

Conservation tillage has been widely adopted as an important and promising sustainable crop management option for mitigation of global climate warming. Although its effects on fluxes in greenhouse gases (GHGs) have been widely studied, contrasting results have been reported, where impacts of reduced and no tillage are unclear. Here, using a dataset with 1286 paired observations extracted from 147 publications, we systematically assessed the effects of reduced vs. no tillage on the fluxes of soil CO2, N2O, and CH4 across the globe. We also assessed how reduced and no tillage may affect the total global warming potential (GWP) of these three GHGs and the associated crop yield. We found that (1) reduced tillage increases N2O and CH4 emissions by 31.0% and 24.7%, respectively, and decreases crop yields by 17.4%, with no effect on CO2 emissions or CH4 uptake; (2) no tillage decreases CO2, N2O, and CH4 emissions, and GWP by an average of 15.1%, 7.5%, 19.8%, and 22.6%, respectively, with no effect on CH4 uptake or crop yield; (3) crop residue retention, cropland type, rotation regime, crop species, and soil physicochemical properties regulate effects of reduced and no tillage, where their impact varies with GHG and tillage type; and (4) there was a lack of relationship between responses of crop yields and GHG fluxes under reduced and no tillage, with the exception of N2O emissions, where they were positively related. Overall, our results showed that reduced tillage stimulates GHG emissions and decreases crop yields, whereas no tillage decreases GHG emissions, with no crop yield tradeoff. These results indicate that no tillage is an effective sustainable crop management practice for the mitigation of climate warming and provision of food security.