Effects of different tillage practices on cropland carbon efficiency in wheat-maize rotation cropping

Enhancing cropland carbon efficiency (CCE) is vital for carbon-neutral and sustainable agricultural development. In this paper, we use the minimum distance to strong efficient frontier with undesirable outputs model and survey data from wheat–maize farmers in the Yellow River Basin of China in 2020 to investigate the effect and mechanism of different tillage practices on CCE. The results show that the average CCE in the study area is 0.592 6, which has large potential for improvement. Among the tillage practices, reduced tillage with straw returning (RTS) achieves the highest mean CCE, followed by no-tillage with straw returning (NTS), and conventional tillage with straw returning performs the worst. Both NTS and RTS are positively associated with higher CCE, with a stronger effect for NTS. Mechanism test results indicate that these practices enhance CCE primarily by increasing yield and net carbon sequestration. NTS improves CCE by reducing energy use and emissions, and RTS tends to increase fertiliser and energy inputs, partially offsetting its efficiency gains. Heterogeneity analysis results further indicate that the positive effects are stronger among small-to-medium-scale, less-educated and elderly farmers. These findings provide micro-level evidence that conservation tillage can promote low-carbon and efficient agricultural production in China.