High‐Resolution Spatiotemporal Analysis of Nitrogen Balance and Use Efficiency in Chinese Annually Planted Cropland (1980–2020)

Nitrogen (N) plays a critical role in sustaining global food production and maintaining ecosystem stability. However, the rapid increase in fertilizer use over recent decades has led to excessive N input that surpasses the N uptake capacity of annually planted cropland, thereby imposing substantial environmental pressures. Optimizing annually planted cropland N utilization has thus become an urgent global challenge. In this study, we quantified the spatiotemporal dynamics of N fluxes in Chinese annually planted cropland at a 5‐arc‐minute resolution from 1980 to 2020 and investigated the factors influencing nitrogen use efficiency (NUE). The results showed that total N input to Chinese annually planted cropland increased markedly during this period, with chemical fertilizer being the dominant source. Concurrently, N output also rose substantially, mainly driven by crop harvests, although its growth rate lagged behind that of N input, resulting in a persistent N accumulation. Spatially, both N input and output were concentrated in intensively cultivated agricultural regions such as North China and the Huang‐Huai‐Hai Plain, whereas lower values were observed in Northwest and Southwest China. The XGBoost model identified soil thickness, soil organic carbon, and temperature as key determinants of NUE, although their relative importance varied across regions. By employing high‐resolution data, this study provides a refined depiction of regional variations in cropland N fluxes and efficiency, overcoming the limitations of previous analyses conducted at administrative scales. The findings offer a robust scientific foundation for improving cropland N management practices and NUE in China, with implications for sustainable agricultural management.