Non-Grain Conversion of Cropping Structure and Agricultural Carbon Emissions: Evidence from China’s County-Level Panel Data

Abstract

China’s non-grain conversion of cropping structure provides an empirical context for understanding how intra-arable crop composition adjustments affect county-level agricultural carbon emissions. However, local governments must simultaneously safeguard food security, farmer incomes, and low-carbon transitions, while farmers adjust crop choices in response to relative returns, production constraints, and policy boundaries. Using an unbalanced panel dataset of Chinese counties from 2000 to 2020, this paper constructs a non-grain conversion rate indicator and employs a two-way fixed-effects model at the county and year levels to examine the relationship between non-grain conversion and agricultural sector carbon emissions. The findings indicate that, after controlling for county fixed effects and annual common shocks, the non-grain conversion rate is significantly and positively correlated with agricultural carbon emissions. This conclusion remains generally robust after winsorization, alternative measures, and adjusted clustering levels. Mechanism results reveal that non-grain conversion creates emission pressures by increasing the proportion of cash crop cultivation, intensifying high-input production practices, and weakening the efficiency advantages of scale and mechanization. Heterogeneity results show that this relationship is stronger in major grain-producing areas, southern paddy field regions, the Yangtze River Economic Belt, counties with higher development levels, and counties with larger populations, while exhibiting different directions in some non-major producing areas, dryland regions, and counties with lower development levels. This paper integrates land use transition, crop composition choice, and agricultural carbon emissions into a unified analytical framework, demonstrating that non-grain conversion governance should not be understood as merely area-based regulation, but rather as institutional coordination embedded among food security, agricultural returns, and low-carbon transitions.