Low-carbon city pilot policy, carbon emission reduction effect of agricultural inputs, and transmission pathways: evidence from a quasi-natural experiment at the prefecture level in China based on multi-period DID

Introduction Low-carbon city pilot policies constitute an important institutional practice for advancing the green and low-carbon transition of agriculture and achieving the “Dual-Carbon” goals. Scientific assessment of the agricultural emission-reduction effects of this policy is critical for land and food security. Methods Based on prefecture-level panel data of China spanning 2005–2024, this paper adopts a multi-period staggered Difference-in-Differences (DID) model to systematically examine the impacts of low-carbon city pilot policies on carbon emissions associated with agricultural inputs, and provides associational evidence on the transmission mechanisms. Given that the conventional two-way fixed-effect multi-period DID may yield potential bias under strong heterogeneity, this study further employs the Callaway-Sant’Anna staggered DID (CS-DID) to estimate the dynamic treatment effects for different cohorts. Multiple robustness strategies including PSM and placebo tests are also applied to validate regression results and improve the credibility of causal inference. Results The study finds that low-carbon city pilot policies significantly reduce regional Agricultural input-related carbon emissions mainly through three pathways: optimizing agricultural factor allocation, forcing the low-carbon transformation of agricultural industrial structure, and improving agricultural energy-use efficiency. Heterogeneity exists in policy effects: western cities achieve the strongest emission-reduction outcomes, provincial-capital cities show substantially stronger carbon-mitigation effects than ordinary prefecture-level cities (significant only at the 10% level in the heterogeneity test), and cities included in the pilot program at an earlier stage deliver greater carbon-reduction efforts for agriculture. Discussion This paper effectively identifies the net agricultural emission reduction effect of the progressive low-carbon policy, supplements empirical evidence on the governance of agricultural non-point source carbon emissions by low-carbon policies, and provides empirical support and decision-making references by region and city administrative level for the national low-carbon transformation of agriculture and the optimization and implementation of differentiated low-carbon policies.