Cropland is trapped outside a safe and agronomically viable nitrogen use

Ensuring productive and environmentally safe cropland systems remains a central challenge in agriculture. However, despite decades of data generation, we lack a consistent understanding of how cropland systems perform relative to environmental and agronomic limits. Here, we develop a framework to classify nitrogen use in national croplands into four operating spaces. Applying it globally to 1961-2022 shows that most countries have operated outside the environmentally safe and agronomically viable space, with sustainable nitrogen use remaining both rare and brief. Even in 2022, most countries would need implausible combinations of yield gains and nitrogen input reductions to enter this space. By 2100, this constraint persists across 17 million scenario trajectories, with no country projected to reach a safe and agronomically viable space. Our findings indicate that crop composition shifts alone are insufficient, reflecting how current scenario narratives omit the governance, technological and institutional transformations needed to enable sustainable nitrogen use.