Pathways towards low-carbon sustainable agriculture: how farmland size affects net carbon emissions

Understanding the impact of farmland size adjustment on net crop carbon emissions (NCEs) is crucial for both effective farmland management and sustainable development, which are essential topics in agri-environmental science. However, studies exploring the relationship between farmland size and NCEs remain limited, particularly in developing countries with scarce farmland, such as China. To fill this gap, this paper discusses farmland size's impact on NCEs using a threshold model combining endogenous switching regression (ESR) and two-stage least squares (2SLS) with survey data from 2600 Chinese farmers. The results show that increasing farmland size curbs the scale and intensity of NCEs. However, their relationship follows a triple threshold effect, where substantial NCEs mitigation occurs only when the per-household farmland size exceeds specific thresholds of 5.1, 15.2, and 46.7 ha. Expanding farmland size can also indirectly reduce NCEs by promoting green agricultural technologies (GAT) adoption. Moreover, lowering farmers' time preferences and enhancing technical training can increase the positive effect of farmland size expansion on GAT adoption and reduce NCEs further. However, the emission reduction effects vary by GAT type. Soil testing and fertilization technology, pest control technology, and water-saving irrigation technology reduce NCEs, while the other GAT have insignificant effects. Overall, our study sheds light on the intricate relationships between farmland size, GAT adoption, and NCEs, and provides valuable insights for low-carbon, sustainable agriculture policies. We suggest that policymakers can reduce NCEs and facilitate agriculture's low-carbon transition by promoting moderate farmland size expansion and locally adapted GAT. Expanding farmland size beyond specific thresholds of 5.1, 15.2, and 46.7 ha significantly reduces NCEs, but this relationship is nonlinear. China should promote appropriate scale management to transition toward low-carbon agriculture.Promoting the widespread dissemination of agricultural carbon mitigation technologies according to local conditions is crucial, especially for large farms to cut carbon emissions.Policymakers should demonstrate the long-term benefits of GAT to raise farmers' valuation of low-carbon agriculture constrained by their time preferences.Governments should provide technology training and learning opportunities to reduce the costs and risks of adopting GAT.