# Urbanization and Grain Production Pattern of China: Dynamic Effect and Mediating Mechanism
## 2 Theoretical Analysis and Hypothesis
The reduction of cropland directly changes the intensity and structure of farmers' production factor inputs and resource inputs. Farm households of different sizes have significantly different value orientations and intensification preferences on cropland utilization [30]. Due to climatic conditions, the planting and cropping system is difficult to change in the short term. The reduction of cropland and farmers' choices could change the extent and potential of cropland utilization. Facing decreases in cropland, the farming practices and cropland utilization adopted by farmers of different regions  
Figure 1: Pathways of urbanization affecting GPP. vary due to the regional heterogeneity of endowment conditions, mainly manifested as regional differences in the MCI [31], which is also the result of farmers' choices in the face of various economic, social, and institutional constraints. Farmers in regions rich in cropland resources could redistribute production funds and factor inputs by adjusting the intensity and structure of production material factor inputs such as chemical fertilizers, pesticides, and agricultural films per unit area of cropland. They may also increase the planting area through hedging and intercropping, thus raising the MCI and improving agricultural production conditions. Farmers in regions with poorer cropland resources often face difficulties in achieving the scale effect, and their willingness to engage in grain production is often reduced. As a result, the likelihood of their abandoning farming and resorting to land circulation increases, leading to a decrease in the MCI. Changes in the cropland utilization, as characterized by MCI, lead to regional variability in grain production, which in turn affects the GPP. Therefore, the following hypothesis can be formulated. **Hypothesis 2 (H2). **_Urbanization affects GPP through changes in the MCI--i.e., cropland utilization plays a mediating role._  
The planting structure (PS) represents the proportion of grain crops in all crops planted. Urbanization promotes the flow of labor. Facing changes in the comparative returns of planting grain crops due to rising production costs, grain farmers must choose between planting grain crops or non-grain crops, which in turn leads to changes in the PS. On the one hand, the increase in non-farm employment opportunities brought about by urbanization contributes to the increase in the income level of rural residents. As a result, food consumption shifts and is upgraded from a focus on sustenance to a focus on food safety and nutrition, which is manifested as a decrease in the direct market consumption of food products and a strong demand for high value-added agricultural products. Thus, changes in the demand structure of agricultural products lead to adjustments in the production structure [2]. On the other hand, the micro-level changes in the GPP are the results of farmers' active choices. Since the rising cost of planting grain crops reduces the comparative returns of grain production and cash crops have higher comparative returns, rational farmers would adjust their farming behavior and planting structure in response to market demand and price changes, thus increasing the possibility of planting non-grain crops. Adjustments in the PS may negatively affect the proportion of grain production in a region, gradually contributing to changes in the GPP. Therefore, the following hypothesis can be formulated. **Hypothesis 3 (H3). **_Urbanization affects GPP through PS--i.e., planting structure adjustment plays a mediating role._  
Due to cropland and labor constraints on grain production brought by the rapid urbanization and the advancement of agricultural market reforms, farmers are enticed to improve land productivity and labor productivity through agricultural technology progress. Agricultural technology progress (ATECH) is mainly achieved through independent technology innovation and technology transfer from non-agricultural industries.