Cost-effective mitigation of nitrogen pollution from global croplands

Cropland is a main source of global nitrogen pollution(1,2). Mitigating nitrogen pollution from global croplands is a grand challenge because of the nature of non point-source pollution from millions of farms and the constraints to implementing pollution-reduction measures, such as lack of financial resources and limited nitrogen management knowledge of farmers3. Here we synthesize 1,521 field observations worldwide and identify 11 key measures that can reduce nitrogen losses from croplands to air and water by 30-70%, while increasing crop yield and nitrogen use efficiency (NUE) by 10-30% and 10-80%, respectively. Overall, adoption of this package of measures on global croplands would allow the production of 17 +/- 3 Tg (10(12) g) more crop nitrogen (20% increase) with 22 +/- 4 Tg less nitrogen fertilizer used (21% reduction) and 26 +/- 5 Tg less nitrogen pollution (32% reduction) to the environment for the considered base year of 2015. These changes could gain a global societal benefit of 476 +/- 123 billion US dollars (USD) for food supply, human health, ecosystems and climate, with net mitigation costs of only 19 +/- 5 billion USD, of which 15 +/- 4 billion USD fertilizer saving offsets 44% of the gross mitigation cost. To mitigate nitrogen pollution from croplands in the future, innovative policies such as a nitrogen credit system (NCS) could be implemented to select, incentivize and, where necessary, subsidize the adoption of these measures.

Automated summary

Cropland is a major contributor to nitrogen pollution, and reducing this pollution is a challenge due to the decentralized nature of the pollution and the limitations in implementing pollution-reduction measures. By analyzing field observations, we have identified key measures that can significantly reduce nitrogen losses from croplands while improving crop yield and nitrogen use efficiency. Implementing these measures on a global scale could lead to significant benefits in food supply, human health, ecosystems, and climate, with relatively low mitigation costs.