Revealing the Process and Mechanism of Non‐Main Grain Cropland Expansion in China

ABSTRACT The conversion of Chinese farmland to non‐main grain cropland (NMGL) threatens national food security, yet its local‐scale dynamics remain poorly understood. Here, we provide a county‐level analysis of the spatiotemporal patterns and drivers of this land‐use change. We identify striking regional disparities: the prevalence of NMGL is highest in major grain consumption areas (22.3%), intermediate in balanced zones (18.4%), and lowest in production areas (11.6%). Between 1985 and 2020, this trend evolved from localized occurrences into a widespread phenomenon. Crop systems influence conversion risks, with single‐cropping systems exhibiting a 2.1–3.8 times higher vulnerability to conversion than intercropped systems. Driver analysis indicates that soil factors (particularly organic carbon) are the primary determinant nationwide (40% contribution), although socioeconomic factors prevail in balanced regions. To effectively preserve China's agricultural land, management frameworks need transition from rigid regulation of non‑grain cropping areas toward a dynamic protection strategy anchored in food‑balance demands. A smarter, system‐wide approach is needed that optimizes planting structures and agricultural layouts. Our study provides critical insights for formulating a food balance demand‐oriented farmland protection strategy.