2015 Nitrogen Expert Panel NUE Indicator
The main resources for global food production (land, soil, water, biodiversity, some nutrient elements) are finite and some even scarce. Moreover wasting resources is often harmful to society and the environment. The pressure on our natural resources is large, and at risk of increasing in the coming decades due to the projected increase in human population in the world and anticipated changes in food consumption patterns.
There is a need for communications about resource use efficiency and for measures to increase the use efficiency of nutrients in relation to food production. This holds especially for nitrogen. Nitrogen (N) is essential for life and a main nutrient element. It is needed in relatively large quantities for the production of amino acids (protein), nucleic acids and chlorophyll in plants. However, excess N pollution is a threat to our health and the environment.
The ambition of the EU Nitrogen Expert Panel is to contribute to improving efficient nitrogen use in food production. Here, we propose an easy-to-use indicator for ‘nitrogen use efficiency’ (NUE), applicable to agriculture and food production–consumption systems. It is based on the mass balance principle, i.e. using N input and N output data for its calculation: NUE = N output / N input. NUE values have to be interpreted in relation to productivity (N output) and N surplus (i.e., the difference between N input and harvested N output).
For estimating NUE and communicating the results, data and information are required about (i) the total N inputs into a system and the N output in harvested products, (ii) the nature of the system (e.g. farm, crop system, livestock housing system, food processing and distribution system) and its boundaries, (iii) the time span of the analyses, and (iv) possible changes in the stock of N in the system. The NUE indicator is easily presented via a two-dimensional input – output diagram. This allows the presentation of NUE, N output and N surplus in a coherent manner, together with possible reference or target values (Figure ES1).
The NUE concept is illustrated in this report with four different cases:
a) for crops at the field scale, using data from four different N fertilization trials,
b) for crop production systems for different EU Member States, based on data for the period 1961 to 2010,
c) for the Gross Nitrogen Balance of agricultural soils for EU Member States, based on a replotting of data from OECD and Eurostat, and
d) for mixed crop-livestock systems (dairy farms), where changes in NUE are analyzed over a 15 years period.
The final discussion chapter concludes that the NUE indicator proposed here is a simple, useful and flexible concept. It allows decision makers to examine differences in NUE between farms, between specific systems, between countries, and between years. Effects of technical progress and of policy measures can be identified. As such, NUE can serve as a valuable indicator for monitoring sustainable development in relation to food production and environmental challenges. By considering limits associate with both excess and insufficient N use, the NUE indicator contributes towards improving N
Nitrogen use efficiency impacts many of the recently proposed/defined Sustainable Development Goals (SDGs) for the post-2015 era, for which concrete targets, pathways and indicators need to be developed at country scale and below. The proposed NUE indicator is suitable for setting realistic targets and monitoring of progress in that context, particularly in relation to SDG 2 (Food and nutrition security), SDG 12 (Sustainable consumption and production), SDG 14 (Marine ecosystems) and SDG 15 (Terrestrial ecosystems).