Nitrogen is a crucial input to food production and yet its oversupply in many parts of the world contributes to a number of environmental problems. Most policies dedicated to reducing agricultural nitrogen pollution focus on changing farmer behaviour. However, farm-level policies are challenging to implement and farmers are just one of several actors in the agri-food chain. The activities of other actors — from fertilizer manufacturers to wastewater treatment companies — can also impact nitrogen losses at the farm level and beyond. Consequently, policymakers have a broader range of policy options than traditionally thought to address nitrogen pollution from field to fork. Inspired by the concept of full-chain nitrogen use efficiency, this Perspective introduces the major actors common in agri-food chains from a nitrogen standpoint, identifies nitrogen policies that could be targeted towards them and proposes several new criteria to guide ex-ante analysis of the feasibility and design of different policy interventions. Sustainably feeding ten billion people by 2050 will require fundamental changes in the global food system — a broad portfolio of policy options and a framework for how to select them is essential.

氮是粮食生产的重要投入，但在世界许多地方，氮的供过于求造成了许多环境问题。致力于减少农业氮污染的大多数政策都着眼于改变农民的行为。但是，农场一级的政策难以实施，农民只是农业食品链中几个参与者之一。从肥料制造商到废水处理公司的其他参与者的活动也可能影响农场乃至整个农场的氮损失。因此，决策者拥有比传统上认为解决从田间到餐桌的氮污染更广泛的政策选择。受全链氮利用效率概念的启发，本《透视》从氮的角度介绍了农业食品链中常见的主要行为者，确定可以针对氮政策的氮政策，并提出一些新标准，以指导事前对各种政策干预措施的可行性和设计进行分析。到2050年，要持续为100亿人口提供食物，将需要全球粮食系统的根本变化-一系列广泛的政策选择以及如何选择这些选择的框架至关重要。