Agricultural Industrial Agglomeration and Agricultural Eco-Efficiency: Theoretical Mechanisms and Empirical Analysis

Addressing the structural contradiction between “large country with small-scale farming” and “ecological constraints” in the process of Chinese-style agricultural modernization necessitates a reexamination of the interactive relationship between industrial spatial organization and eco-efficiency. Based on provincial panel data from 2004 to 2023, this paper constructs an analytical framework encompassing four dimensions—scale, technology, structure, and society—and employs double/debiased machine learning models to systematically examine the effects of agricultural industrial agglomeration on agricultural eco-efficiency. The findings are as follows: (1) The impact exhibits a U-shaped dynamic pattern of “initial suppression followed by later promotion.” (2) The mechanism analysis identifies four transmission pathways—economies of scale, technological innovation, industrial structure, and agricultural socialized services. Among these, technological innovation, agricultural socialized services, and industrial structure rationalization exhibit significant positive transmission effects, whereas economies of scale generate a negative net effect due to over-intensive factor inputs, and the mediating effect of industrial structure sophistication has not yet materialized. (3) Agricultural technological innovation exhibits a significant double-threshold effect and serves as the key variable for unlocking the eco-efficiency benefits of agglomeration. (4) Agricultural industrial agglomeration exerts significant negative spatial spillover effects on neighboring regions, with this effect being more pronounced in western China, low-agglomeration areas, and non-major grain-producing regions. This study elucidates the nonlinear dynamics and spatial externalities of agglomeration’s ecological effects, providing a basis for differentiated agricultural environmental policies and cross-regional ecological collaborative governance.