Beyond single regulation: how does green agriculture comprehensive pilot achieve fertilizer reduction? Evidence from China

Introduction Compared with single regulation, the Green Agriculture Comprehensive Pilot (GACP) is a comprehensive pilot policy promoted by China to advance agricultural green transformation. However, few questions remain unclear whether and how this policy reduce the fertilizer use. Methods Using panel data of 106 cities from 8 Chinese central and eastern provinces over 20002022, this study adopts difference-in-differences (DID) and causal mediation analysis (CMA) to evaluate GACP’s effect on fertilizer application density, identifying its underlying mechanisms and heterogeneities, and discuss its implications for food security. Results The results show that the GACP effectively reduces fertilizer use, decreasing the average annual fertilizer per unit of sown area in pilot cities by 9.9% (44.046 kg/ hm2). The reduction effect initially strengthens but then gradually weakens over time, but remains effective throughout the observation period, these results remaining robust after a series of tests. Mechanism analysis indicates that the GACP reduces fertilizer use by establishing a green agricultural support system and promoting four internal institutional incentive mechanisms: technological progress, scale operation, professional division, and industrial convergence, with respective contributions of 11.15%, 5.46%, 12.66%, and 8.12%. Heterogeneity analysis shows that the reduction effect strengthens with higher chemical fertilizer use; the GACP promotes reductions in nitrogen and phosphorus fertilizers, but leads to structural substitution and optimization, increasing the use of compound fertilizers at the expense of single-nutrient fertilizers. Furthermore, the GACP is more pronounced in non-grain producing regions (NGPR), economically underdeveloped regions, areas with relatively flat terrain, and highly digitized regions. Furthermore, the fertilizer reduction effect of GACP poses potential risks to food security. Although no evidence verifies that GACP decline the total grain production, it significantly reduces grain production capacity in NGPR and shift the regional planting structures. Discussion Based on the above research, it is recommended to summarize and scale up effective GACP practices while mitigating diminishing marginal policy effects, implement gradient precision reduction management tailored to regional inherent fertilization features, adopt classified targeted governance matching local external conditions, and advance the coordinated progress of fertilizer green reduction and food security under agricultural functional zoning, to jointly facilitate high-quality green agricultural development.