Unlocking nitrogen management potential via large-scale farming for air quality and substantial Co-benefits

China's sustained air quality improvement is hindered by unregulated ammonia (NH3) emissions from inefficient nitrogen management in smallholder farming. Although the Chinese government is promoting a policy shift to large-scale farming, its benefits when integrated with nitrogen management remain unclear. Here we fill this gap using an integrated assessment by combining geostatistical analysis, high-resolution emission inventories, farm surveys, and air quality modeling. The smallholder-dominated farming allows only 13%–31% NH3 reduction, leading to limited PM2.5 decreases nationally due to nonlinear PM2.5 chemistry. Conversely, large-scale farming would double nitrogen management adoption rates, increasing NH3 reduction potential to 48%–58% and decreasing PM2.5 by 9.4–14.0 μg·m−3 in polluted regions. The estimated PM2.5 reduction is conservative due to localized NH3-rich conditions under large-scale livestock farming. This strategy could prevent over 300 000 premature deaths and achieve a net benefit of ${\$}$68.4–86.8 billion annually, unlocking immense benefits for air quality and agricultural sustainability.