Indicators to evaluate agricultural nitrogen efficiency of the 27 member states of the European Union

doi:10.1016/j.ecolind.2016.02.007

Ecological Indicators

Volume 66, July 2016, Pages 612-622

https://doi.org/10.1016/j.ecolind.2016.02.007 Get rights and content

Highlights

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Three novel nitrogen indicators were tested at the national scale.
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The nitrogen indicators are relevant tools for comparing agricultural systems.
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Studying their change over time provides useful information to decision makers.
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Including changes in soil N increased indicator uncertainty.
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Potential N efficiency was assessed for EU-27 countries.

Abstract

Nitrogen (N) use in European agriculture is not efficient, with less than one third of available N recovered in intended outputs. Over two thirds of N is lost to the environment, where it has negative ecological, social and economic consequences. Improving N efficiency in crop and animal production is a priority to reduce its detrimental effects while maintaining food production. The territory scale is particularly suitable for evaluation of N efficiency because it is used for environmental impact assessment and public policies. However, N Use Efficiency (NUE), the efficiency indicator available at this scale, has several limitations: (i) inputs and outputs can vary depending on the boundaries and definitions used, (ii) input production and transport are not always included, and (iii) changes in soil N stock are rarely considered. Three indicators were recently developed at the farming system scale to overcome NUE limitations. System N efficiency (SyNE) expresses N in intended outputs as a function of all major N inputs and losses. Relative N efficiency (RNE) expresses N efficiency relatively to its potential given the nature of productions. System N balance (SyNB) expresses N losses from cradle to the gate of the farm. All three indicators include N losses due to the production and transport of inputs and soil N stock variations. The current study tested these indicators at the national scale to provide a better understanding of N management in 27 European countries. The study demonstrates the feasibility and utility of calculating these indicators at the national scale. The mean NUE of European countries is 0.35, while their mean SyNE is 0.23, highlighting the importance of considering soil N loss in efficiency indicators. Average SyNB is 113 kgN ha⁻¹ AA, but varies from 31 to 432 kgN ha⁻¹ AA, showing the large margin of progress of some countries regarding N losses. Mean RNE is 0.43, which means that European countries could maintain their production with much less N inputs. The systems approach enables relevant comparisons among countries with different production methods and intensities. Combining SyNE and SyNB provides complementary information about the agricultural use of N resources and the resulting environmental pressure. RNE assesses the progress margin of each country based on its production and enriches the efficiency analysis by considering the nature of agricultural products. These indicators are promising tools to study, compare and improve the N efficiency of territories or countries.

Introduction

The European Union (EU) is one of the most intensive agricultural regions per unit of surface area (Haberl et al., 2007, Monfreda et al., 2008). This productivity is supported by the massive use of agricultural inputs, mostly nitrogen (N) fertilizers (Mueller et al., 2012) and imported feedstuff (Lassaletta et al., 2014). However, only 31% of agricultural N inputs are recovered in intended products at the European scale (Leip et al., 2011b). This low N efficiency results in major N losses, which have problematic impacts on water, air and soil quality as well as ecosystem functions, biodiversity and human health (Sutton et al., 2011). Rockstrom et al. (2009) identified the disruption of the biogeochemical N cycle as one of the main threats to future human development. Improving N efficiency, defined as the ratio between N in intended agricultural products and N used to produce them, is crucial to reduce this environmental impact while also providing enough food, feed, fuel and fiber to the growing population (Sutton et al., 2011).

The territory scale is a particularly important research challenge. It integrates all biogeochemical flows and provides additional solutions compared to those at smaller scales (e.g. manure exchange, landscape management, wastewater treatment). It allows analysis of specific national agricultural trends and policies, such as the EU Common Agricultural Policy (Velthof et al., 2014) to prioritize actions that limit environmental risks (Leip et al., 2011a). Indicators that quantify N efficiency are necessary to improve it at the territory scale.

Most N management indicators at the territory scale focus on estimating N losses through modeling approaches (Moreau et al., 2013) or N balances such as the farm-gate balance (FGB; Dalgaard et al., 2012). N footprint indicators (Galloway et al., 2014) have also been developing recently. They consider the whole food chain (input and food production, food processing and consumption), and can include other human activities such as energy use. The most used N efficiency indicator is called nitrogen use efficiency (NUE; Leip et al., 2011b, Liu et al., 2008). This indicator is recommended as an agro-environmental indicator for the Common Agricultural Policy (European Commission, 2000). The United Nations Economic Commission for Europe considers it a legal tool for implementing the Gothenburg Protocol on air pollution (UNECE, 2012). However, both FGB and NUE have several limitations:

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Considered inputs and outputs can vary depending on the boundaries and definitions used by the authors. For instance, manure output can be considered an output, a negative input or is ignored in indicators calculation (Dalgaard et al., 2012, Simon et al., 2000, Spears et al., 2003)
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N emitted during production and transport of inputs is not always included (Schröder et al., 2003, Sutton et al., 2013)
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changes in soil N are rarely considered in the calculation of indicators due to the lack of data (de Vries et al., 2011, Özbek and Leip, 2015)
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NUE is calculated as a ratio between N outputs and inputs. Thus, if the same quantity of N is added on both input and output sides, the ratio tends towards one. This mathematical bias favors farms that buy animal feed and sell crops against those that feed their animals with their crops (Godinot et al., 2014, Schröder et al., 2003).

A novel indicator, system nitrogen efficiency (SyNE; Godinot et al., 2014), is based on NUE but resolves its limitations. SyNE presents some similarities with existing N footprint indicators, but focuses on the efficiency of agricultural systems to transform N inputs into intended N outputs, while N footprint indicators usually focus on N losses due to the consumption patterns of end-consumers. Similarly, system nitrogen balance (SyNB; Godinot et al., 2014) is based on FGB and resolves its limitations. As the novel indicators are based on existing indicators that have been used at the territory scale, they should also be applicable to this scale.

Several authors claim that N efficiency is linked to the type of production system considered (Schröder et al., 2003, UNECE, 2012). By nature, a farming system or a territory with mostly animal production will be less efficient than a system with mostly crops. The relative nitrogen efficiency (RNE) indicator addresses these biological differences by expressing efficiency relative to the maximum attainable efficiency of each product (Godinot et al., 2015).

The goal of this study was to apply the three indicators presented above (SyNE, SyNB and RNE) to the 27 member states of the EU to test their ability to describe N management at the territory scale and each member state's progress margin in N efficiency.

Section snippets

Indicator calculation

SyNE, SyNB and RNE were calculated at the national scale, as follows: $\begin{array}{l} S y N E = \frac{\sum_{i = 1}^{n} n e t o u t p u t_{i}}{\sum_{j = 1}^{m} n e t i n p u t_{j} + \sum_{k = 1}^{p} i n d i r e c t l o s s_{k} - Δ N_{s o i l}} \\ S y N B = {\sum_{j = 1}^{m} n e t i n p u t}_{j} + \sum_{k = 1}^{p} i n d i r e c t l o s s_{k} - Δ N_{s o i l} - \sum_{i = 1}^{m} n e t o u t p u t_{i} \\ a t t a i n a b l e e f f i c i e n c y = \frac{\sum_{i = 1}^{n} n e t o u t p u t_{i}}{\sum_{i = 1}^{n} n e t o u t p u t_{i} / a t t a i n a b l e e f f i c i e n c y_{i}} \\ R N E = \frac{S y N E}{a t t a i n a b l e e f f i c i e n c y} \end{array}$ where: $\sum_{i = 1}^{n} n e t o u t p u t_{i}$ is the sum of the n net N outputs by crops and animal products, $\sum_{j = 1}^{m} n e t i n p u t_{j}$ is the sum of the m net N inputs from organic and inorganic fertilizers, feed, seeds, manure,

National N flows

Fig. 2 and Table 2 present the mean annual N flows for each of the EU-27 member states for the 2000–2008 period. All means calculated in this work are unweighted arithmetic means, in order to compare countries to a collective reference with no effect of size. Mean net animal output was 22 kg N ha⁻¹ AA and ranged from 4 to 108 kg N ha⁻¹ AA. Mean net crop output was 11 kg N ha⁻¹ AA and ranged from 0 to 32 kg N ha⁻¹ AA. During this period, 10 member states had net outputs composed of over 60% animal products.

Conclusion

This study demonstrates the feasibility and utility of calculating N efficiency and balance indicators at the national scale. The three indicators developed (SyNE, SyNB and RNE) are not directly comparable to existing references due to methodological differences but are consistent with them. The indicators are calculated according to a systems approach that includes activities upstream of agricultural production (from cradle to farm gate). This integrative approach enables relevant comparisons

Acknowledgements

The authors are grateful to Michelle and Michael Corson for English proofreading. They also thank two anonymous reviewers whose comments and suggestions improved this manuscript.

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Indicators to evaluate agricultural nitrogen efficiency of the 27 member states of the European Union

Highlights

Abstract

Introduction

Section snippets

Indicator calculation

National N flows

Conclusion

Acknowledgements

Environ. Pollut.

Agric. Syst.

Agric. Syst.

Environ. Dev.

Environ. Pollut.

Agric. Syst.

Eur. J. Agron.

Agric. Ecosyst. Environ.

Agric. Ecosyst. Environ.

Eur. J. Agron.

J. Dairy Sci.

Curr. Opin. Environ. Sustain.

Sci. Total Environ.

Chemosphere

Biological Nitrogen Fixation (BNF) in Europe (No. Legume Futures Report 1.5)

Carbon losses from all soils across England and Wales 1978–2003

Nature

Estimation of global NH3 volatilization loss from synthetic fertilizers and animal manure applied to arable lands and grasslands

Glob. Biogeochem. Cycles

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Biogeosci. Discuss.

The European carbon balance. Part 2: Croplands

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Farm nitrogen balances in six European agricultural landscapes, a method for farming system assessment, emission hotspot identification, and mitigation measure evaluation

Biogeosci. Discuss.

EMEP MSC-W Modelled Air Concentrations and Depositions [WWW Document]

Indicators for the Integration of Environmental Concerns into the Common Agricultural Policy (No. COM(2000) 20)

Eurostat Database [WWW Document]

Eurostat (2013). Nutrient Budgets – Methodology and Handbook. Version 1.02

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