Cost-effective mitigation of nitrogen pollution from global croplands

TLDR

Cropland is a major source of global nitrogen pollution, and mitigating it is a grand challenge due to non‑point‑source pollution from millions of farms and constraints such as limited financial resources and farmers’ nitrogen‑management knowledge. The study synthesizes 1,521 field observations to identify 11 key measures that can reduce nitrogen losses by 30–70% while boosting yield and NUE, and proposes that future mitigation could be supported by policies such as a nitrogen credit system to incentivize adoption. The authors synthesized 1,521 field observations worldwide to identify 11 key measures that can reduce nitrogen losses to air and water by 30–70% while increasing crop yield and NUE by 10–30% and 10–80%. Adopting the package of measures globally would increase crop nitrogen production by 20 % (17 ± 3 Tg), reduce fertilizer use by 21 % (22 ± 4 Tg), and cut nitrogen pollution by 32 % (26 ± 5 Tg), yielding a global societal benefit of 476 ± 123 billion USD with net mitigation costs of only 19 ± 5 billion USD, of which 44 % are offset by fertilizer savings.

Abstract

Abstract 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 farmers 3 . 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.