Mega-analysis of no-tillage and reduced tillage impacts on crop yields and greenhouse gas emissions

Agriculture contributes 11 % of total anthropogenic greenhouse gas (GHG) emissions, including carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). Conservation tillage practices such as no-tillage (NT) and reduced tillage (RT) are promoted as climate-smart strategies to mitigate GHG emissions without compromising crop yields. However, existing meta-analyses have produced contradictory results regarding the effects of these practices on crop yields and soil GHG emissions. To address these discrepancies, we conducted a mega-analysis, synthesizing data from 30 meta-analyses to comprehensively assess the impacts of the NT, RT, and mixed NT+RT on crop yields and GHG emissions. Our results showed that the tillage treatments (NT, RT, and mixed NT+RT) exhibited no significant overall effect on crop yields. NT did not influence soil CO₂ emissions, and none of the tillage treatments influenced soil CH₄ emissions. However, NT increased soil N₂O emissions by 10.5 % (0.010, 95 % Confidence interval: 0.067, 0.132), whereas RT and NT+RT had no significant effect on soil N₂O emissions. The varied impacts of tillage treatments were attributed to the interactions among experimental settings, soil properties, and agriculture practices such as crop residue management, irrigation type, and nitrogen fertilizer application rate. This mega-analysis provides a more comprehensive quantification than individual meta-analyses, offering valuable insights into the impacts of conservation tillage practices on crop yields and GHG emissions.