Non-Linear Effects of Driving Forces on Agricultural Green Development: A Panel Threshold Analysis in Hunan Province, China

Agricultural green development (AGD) is crucial for food security, eco-efficiency, and rural sustainability. However, existing studies seldom examine structural shifts in AGD drivers across development stages. Using 2004–2023 county data from Hunan, we measure AGD via combined-weighting–TOPSIS and apply a panel threshold model with lagged agricultural economic level as the threshold. Results show the following: (1) AGD in Hunan generally rose, accelerating in later years, with a distinct “east-strong, west-weak” pattern; (2) a significant double threshold exists at approximately CNY 1959 and CNY 3380 per capita; the green effects of agricultural service provision and mechanization are progressively released, non-farm employment shows an inverted U-shape, while fiscal support shows no significant effect; (3) the release patterns of service provision and mechanization are common in middle and high stages, whereas the effect of non-farm employment varies markedly across Hunan’s four subregions. By endogenizing development stage as a testable threshold, this study reveals stage-dependent driving rules of AGD and provides a reference for differentiated green-transition pathways and regional governance in major grain-producing areas.