## 2 Materials and Methods  
### Research Hypotheses  
#### 2.1.1 The Spatial Spillover Effect of Environmental Regulation on Agricultural Green Development  
Agricultural green development mostly depends on the formulation and enforcement of environmental regulations. Research on the spatial spillover effects of environmental regulation on agricultural green development mainly focused on three perspectives. First, according to the \"strong porter hypothesis\", the stronger the intensity of environmental regulation, the more conducive to curbing agricultural carbon emissions [15]. Moreover, the variation of local government's environmental governance level from bottom competition to definite competition is conductive to produce a significance spatial spillover effect on the environmental governance of adjacent regions [16]. For example, to deal with ecological degradation, the G7 countries have adopted environmental regulations and various measures to reduce carbon emissions [11]. Moreover, the public voluntary environmental regulation also has a positive effect in promoting agriculture green development in adjacent regions through the element flow of labor, technology and other production factors in the local area [7]. Second, as the agricultural carbon emission trading market is still in the exploratory stage, market-motivated environmental regulation shows no significant impact on both local and adjacent regions [7]. Furthermore, local governments also excessively emphasize the importance of environmental regulation means while ignoring technology and other means, thus weakening the positive externalities of environmental governance, which hinder the communication and exchange of adjacent regions, resulting in the negative externalities of environmental governance. Previous research found that environmental regulation was characterized by an emphasis on treatment and light focus on prevention, which could not promote the development of agricultural technology and inhibit agricultural pollution emission [17]. That is, a negative spillover effect of environmental governance on the spatial environment would be generated [17; 18]. Third, environmental regulation shows no significant impact on agricultural green production efficiency when measuring the investment amount of environmental governance [19] while showing a nonlinear \"U-shaped\" relationship by measuring agricultural pollution intensity [20]. Some countries have adopted high-intensity environmental regulation means [21]. Therefore, agricultural operators have to comply with relevant environmental regulation requirements and pay high environmental protection costs, which could be in conducive to promote agricultural green development in both local and adjacent regions. Thus, this paper puts forward the following hypothesis:  
**Hypothesis 1 (H1)**. _Environmental regulation has a negative spatial spillover effect on agricultural green development; that is, local environmental regulation has a restraining effect on agricultural green development in adjacent regions._  
1.2 The Spatial Spillover Effect of Financial Support for Agriculture on Agricultural Green Development  
Relevant studies at home and abroad on the spatial spillover relationship between financial support for agriculture and agricultural green development have explored the two aspects. On the one hand, local financial support for agriculture could promote the agglomeration of information, technology and talents in the local region, which is conducive to the information exchange and knowledge spillover of the agricultural environment in the local region, as well as the diffusion of technology and knowledge in adjacent regions, promoting agricultural green development in both local and adjacent regions [6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21].