Discrepancies exist on the impact of tillage on soil CO₂ emissions and on the main soil and environmental controls. Results from a meta-analysis using 174 paired observations comparing CO₂ emissions over entire seasons or years from tilled (untilled) soils across different climates, crop types and soil conditions show that on average: (1) tilled soils emit 21 % more CO₂ than untilled soils; (2) the difference increase to 29 % in sandy soils from arid climates with low soil organic carbon content.