Ridge-furrow cropping of maize reduces soil carbon emissions and enhances carbon use efficiency

•Ridge tillage reduces carbon emission (CE) with a higher CE efficiency (CEE).•Half mulching reduces CE, and CE per unit of water (WUECE) and enhances CEE.•CE increases with increase of irrigation and middle irrigation enhances CEE.•A positive synergistic effect is determined between CE and maize yield in dry year.•Ridge cropping with half mulching and middle irrigation is an optimum management.