Guidance Document on NUE indicators of the global project INMS

The Guidance Document on NUE indicators has been written in the context of the global project INMS. The Guidance Document, signed by 46 specialists from 19 countries, comprises six sections and 18 chapters covering those aspects considered critical to review, harmonise and update the knowledge on NUE to be used beyond by scientists, practitioners, and policymakers. This document critically analyses different definitions, methods, approaches, considerations, unconventional aspects, exceptions, and uncertainties concerning NUE indicators.

Directing the highest proportion of N injected into agricultural systems to food rather than to the environment is paramount. The nitrogen use efficiency (NUE) indicator deals with this challenge and can be generally defined as the proportion of the N inputs that is retained in agricultural outputs. This simple and widely used parameter is still a major misunderstanding source (Zhang et al., 2021). As is analysed throughout this Guidance Document, there are many different definitions, systems, scales and approaches that should be well known in order to precisely understand what we mean when we talk about NUE. This INMS Guidance will contribute to reducing imprecise use of the term while encouraging harmonisation and comparability.