towards joined-up nitrogen guidance for air, water and climate … · 2019-06-03 · towards...
TRANSCRIPT
Towards joined-up nitrogen guidance
for air, water and climate co-benefits.
Report from the Joint DG ENV & TFRN workshop:
Brussels, October 11th and 12th, 2016
Introduction
The Directorate-General for Environment of the European Commission (DG Environment) and the UNECE
Task Force on Reactive Nitrogen (TFRN) recognize that while nitrogen provides benefits, it also poses
threats across the environment, and that implimenting a joined-up perspective across the nitrogen cycle
should offer many co-benefits. In Brussels on the 11th and 12th of October, 2016, a “Joint DG Environment
& TFRN workshop” was held to discuss the development of an EC/UNECE Guidance Document that would
address a ‘joined-up approach’ to Nitrogen Management in Agriculture.
Currently such guidance documentation is typically separated according to environmental issue and nitrogen
form. The workshop explored how best to provide guidance on integrated management to achieve targets
for ammonia emission reduction, for nitrate leaching losses to groundwater and surface waters, and for
nitrous oxide emission reduction in a more effective and efficient way. This would also include synergistic
side-effects related to air and water quality, climate change, biodiversity and human health that can be
achieved.
With a focus on European agricultural practices as a starting point, the workshop brought together existing
guidance on how to reduce the adverse effects of nitrogen use, while maximizing its benefits for food and
energy supply. Working groups were set up under the following themes.
Theme 1: Principles of overall N management
Theme 2: Housed livestock, manure storage, manure processing
Theme 3: Field application of organic and inorganic fertilizers
Theme 4: Land use and landscape management
Background documents were prepared prior to the workshop, to support and inform working group
discussions. Each group discussed how to best address different parts of the agricultural system,
opportunities for synergy and avoidance of trade-offs, and the preparation of an outline for a future “EC /
UNECE Guidance Document on Joined-up Nitrogen Management in Agriculture”.
This report provides the background documents and working group reports for each theme, and concludes
with the suggested key headings for a future “EC/UNECE Guidance Document on Joined-up Nitrogen
Management in Agriculture”.
This draft document is in copyright. It may not be quoted and graphics reproduced; instead reference
should be made to the original documents.
Contents 1 Principles of overall nitrogen management: background document .............................................................. 7
1.1 Nitrogen management ........................................................................................................................... 7
1.2 Dimensions of integration ................................................................................................................... 11
1.2.1 Vertical integration ..................................................................................................................... 11
1.2.2 Horizontal organization .............................................................................................................. 11
1.2.3 Integration of other elements and compounds ............................................................................ 12
1.2.4 Stakeholder involvement and integration ................................................................................... 12
1.2.5 Regional integration ................................................................................................................... 13
1.3 Tools for integrated approaches to N management ............................................................................. 14
1.3.1 Nitrogen balances ....................................................................................................................... 15
1.3.2 Integrated assessment modeling ................................................................................................. 15
1.3.3 Logistics and chain management ................................................................................................ 15
1.3.4 Stakeholder dialogue .................................................................................................................. 16
1.4 Elements of integrated nitrogen management ..................................................................................... 17
1.4.1 Integrated management pracitices .............................................................................................. 17
1.4.2 Farm Nitrogen Budgets .............................................................................................................. 19
1.5 Measures to prevent and abate ammonia emissions ............................................................................ 24
1.5.1 Livestock feeding strategies ....................................................................................................... 24
1.5.2 Animal Housing ......................................................................................................................... 26
1.5.3 Manure Storage .......................................................................................................................... 27
1.5.4 Manure application techniques ................................................................................................... 28
1.5.5 Fertilizer application techniques ................................................................................................. 29
1.6 Measures to decrease the risk of nitrate leaching losses ..................................................................... 31
1.6.1 The Nitrates Directive ................................................................................................................ 31
1.7 Recommendations for measures under the Nitrates Directive ............................................................ 36
1.7.1 Example recommendations for measures ................................................................................... 38
1.7.2 The capacity and construction of storage vessels for livestock manure. .................................... 39
1.7.3 Limitation of the land application of fertilizers. ......................................................................... 42
1.8 References ........................................................................................................................................... 43
2 Principles of overall nitrogen management: working group report .............................................................. 45
3 Housed livestock, manure storage, and manure processing: background document ................................... 47
3.1 Why do we have emissions and how can they be influenced – the basics behind emission processes 47
3.1.1 Ammonia .................................................................................................................................... 48
3.1.2 N2O and N2 ............................................................................................................................... 49
3.2 Livestock feeding ................................................................................................................................ 50
3.2.1 Feeding strategies for dairy and beef cattle ................................................................................ 51
3.2.2 Feeding strategies for pigs .......................................................................................................... 52
3.2.3 Feeding strategies for poultry ..................................................................................................... 52
3.3 Livestock Housing .............................................................................................................................. 53
3.3.1 Cattle housing ............................................................................................................................. 53
3.3.2 Pig housing ................................................................................................................................. 55
3.3.3 Poultry housing........................................................................................................................... 57
3.3.4 Housing systems for laying hens ................................................................................................ 57
3.3.5 Housing systems for broilers ...................................................................................................... 58
3.4 Manure Storage and Processing .......................................................................................................... 58
3.4.1 Conclusions, final remarks and research questions .................................................................... 66
3.5 References ........................................................................................................................................... 68
4 Housed livestock, manure storage, manure processing: working group report ............................................ 71
4.1 Housing ............................................................................................................................................... 71
4.2 Livestock Feeding ............................................................................................................................... 72
4.3 Treatment ............................................................................................................................................ 72
4.3.1 Aims of manure treatment .......................................................................................................... 72
4.3.2 Slurry treatment .......................................................................................................................... 72
4.3.3 Storage ........................................................................................................................................ 72
4.4 N guidance document .......................................................................................................................... 73
4.4.1 Aspects of N guidance document ............................................................................................... 73
5 Field application of organic and inorganic fertilizers: Background Document ........................................... 74
5.1 Types and quantities of materials being applied ................................................................................. 74
5.1.1 Inorganic mineral fertilizers ....................................................................................................... 75
5.1.2 Livestock manures ...................................................................................................................... 75
5.1.3 Other organic N amendments ..................................................................................................... 76
5.1.4 Crop residues .............................................................................................................................. 76
5.1.5 Grazing returns ........................................................................................................................... 76
5.1.6 N fixation .................................................................................................................................... 76
5.1.7 Current estimates of Nitrogen losses .......................................................................................... 77
5.1.8 Spatial distribution across Europe .............................................................................................. 78
5.1.9 Management practices and influence on N losses ...................................................................... 79
5.1.10 Inorganic mineral fertilizers ....................................................................................................... 80
5.1.11 Livestock manures ...................................................................................................................... 81
5.1.12 Legumes and crop residues ........................................................................................................ 82
5.1.13 Grazing returns ........................................................................................................................... 82
5.1.14 Nitrogen use efficiency and precision management ................................................................... 82
5.1.15 Water and N use efficiency ........................................................................................................ 83
5.2 References ........................................................................................................................................... 85
6 Field application of organic and inorganic fertilizers: working group document ........................................ 87
6.1 Group composition .............................................................................................................................. 87
6.2 Boundaries .......................................................................................................................................... 87
6.3 Knowledge and data gaps .................................................................................................................... 87
6.4 Next steps ............................................................................................................................................ 91
7 Land use and landscape management: background documents ................................................................... 92
7.1.1 Introduction ................................................................................................................................ 92
7.1.2 Why consider landscape level management? ............................................................................. 92
7.1.3 Nitrogen flows in the rural landscape ......................................................................................... 94
7.1.4 Air pollution and related greenhouse gas emissions ................................................................... 95
7.1.5 Surface and groundwater pollution ............................................................................................. 95
7.1.6 Scale issues ................................................................................................................................. 95
7.2 Summary and conclusions ................................................................................................................... 96
7.3 References ........................................................................................................................................... 99
8 Land use and landscape management: working group report .................................................................... 100
8.1 Summary and conclusions ................................................................................................................. 100
8.2 Nature of the problem ....................................................................................................................... 100
8.3 Approaches........................................................................................................................................ 100
8.4 Key findings/state of knowledge ....................................................................................................... 101
8.5 Major uncertainties/challenges .......................................................................................................... 101
8.6 Recommendations ............................................................................................................................. 101
9 Plans for a future joined up guidance document ........................................................................................ 102
9.1 Key questions regarding a guidance document ................................................................................. 102
10 DG-ENV Guidance Document – A skeleton plan for a future “EC/UNECE Guidance Document on
Joined-up Nitrogen Management in Agriculture”. ............................................................................................. 104
10.1 Feedback on document structure ....................................................................................................... 104
10.2 Suggested skeleton structure of a joined up guidance document ...................................................... 105
11 Existing guidance .................................................................................................................................. 108
Figures and Tables
Figure 1. Conceptual visualization of vertical and horizontal integration of firms in production chains. ............ 11 Figure 2. Concept of the nitrogen input – output mass balance of mixed crop – livestock production systems. The
‘hole of the pipe’ model .............................................................................................................................. 14 Figure 3. A farm N budget of a mixed crop-animal production farm. .................................................................. 19 Figure 4. Components of a soil surface N balance of agricultural land. ............................................................... 20 Figure 5. The Environmental Stratification of Europe. ........................................................................................ 34 Figure 6. Map showing the surface runoff risk potential for agricultural land within the Environmental Zones in
the EU-27. ................................................................................................................................................. 35 Figure 7. Map showing the leaching risk potential for agricultural land within the Environmental Zones in the EU-
27.. .............................................................................................................................................................. 36 Figure 8. Forms of reactive nitrogen .................................................................................................................... 48 Figure 9. NH3 concentration in the solution depending on temperature for pH 7.0 and pH 7.5 .......................... 49 Figure 10. Leakage model for N2O and NOx losses during nitrification and denitrification ................................ 49 Figure 11. Changes in slurry composition to be achieved by successful manure treatment ................................. 60 Figure 12. Options of manure treatment ............................................................................................................... 61 Figure 13. Estimate of N inputs to agricultural soils for EU28 for 2014. ............................................................. 74 Figure 14. Estimates of N losses from agricultural soils in EU28 for 2014. ........................................................ 77 Figure 15. Estimates of spatial distribution of mineral fertilizer and manure N to agricultural land for 2005. .... 78 Figure 16. Conceptual framework of the N use efficiency (NUE) indicator ........................................................ 83 Figure 17. Simplified overview of nitrogen flows highlighting major anthropogenic sources, the cascade of
reactive nitrogen forms ............................................................................................................................... 94 Figure 18. Nitrogen flows in rural landscape........................................................................................................ 95 Figure 19. Conceptual model of the shallow groundwater bodies and their interaction with dependent aquatic
ecosystems in the Odense Pilot River Basin, Denmark. ............................................................................. 95
Table 1. Nsurplus and NUE indicators of farming systems, with typical values for specialized crop production
farms, specialized animal production farms and mixed farms .................................................................... 21
Table 2. Indicative ranges for target N surplus and NUE ..................................................................................... 22
Table 3. Indicative target protein levels (%) of dry feed with a standard dry matter content of 88% for housed
animals ........................................................................................................................................................ 25
Table 4. Ammonia emission reduction techniques for animal housing, their emission reduction levels and
associated costs ........................................................................................................................................... 27
Table 5. Ammonia emission reduction techniques for manure storages, their emission reduction levels and
associated costs ........................................................................................................................................... 28
Table 6. Ammonia emission reduction techniques for manure application, their emission reduction levels and
associated costs ........................................................................................................................................... 29
Table 7. Ammonia emission reduction techniques for application of urea- and ammonium-based fertilizers, their
emission reduction levels and associated costs ........................................................................................... 30
Table 8. The 13 Environmental Zones (EnZs) as the first layer of information for pedo-climatic zonation in
Europe. ........................................................................................................................................................ 33
Table 9. Ranking of precipitation surpluses per month per environmental zone .................................................. 39
Table 10. Minimum manure storage capacity (months of manure production) per environmental zone (ENZ) based
on the probability of a precipitation surplus, periods of drought and frost and unforeseeable weather
extremes ...................................................................................................................................................... 41
Table 11. Problems resulting from slurry high dry matter and carbon content..................................................... 59
Table 12. Assessment of impacts achieved by slurry mixing ............................................................................... 61
Table 13. Assessment of impacts achieved by dilution with water ...................................................................... 62
Table 14. Assessment of impacts achieved by slurry aeration.............................................................................. 63
Table 15. Assessment of impacts achieved by slurry separation .......................................................................... 64
Table 16. Assessment of impacts achieved by anaerobic digestion ...................................................................... 65
Table 17. Landscape management impact on nitrogen losses .............................................................................. 96
Principles of overall nitrogen management:
background document
Author: Oene Oenema
The following chapter provides an overview on principles and guidelines for integrated nitrogen (N)
management in agriculture and was used as a background document by the “principles of overall
nitrogen management working group”.
1.1 Nitrogen management
Nitrogen (N) is essential for life and plays a key role in food production. Nitrogen is the most important
crop-yield limiting factor in the world, together with water (Mueller et al., 2013). That is why farmers
apply N fertilizers, which became available and affordable in affluent countries from the 1950s and
more recently in almost all countries (Smil, 2000). However, too much N leads to pollution, which is
harmful for the functioning of our ecosystems and our health (Box 1). The management of N is therefore
important, especially in agriculture, which is the biggest user of N in the world.
Nitrogen management in agriculture aims at achieving agronomic objectives (farm income, high crop
and animal productivity) and environmental objectives (minimal N losses) simultaneously. However,
N management is not easy, because the N cycle is complex (Box 2) and N is easily lost from agriculture
into the environment. Nitrogen is a constituent of all plant and animal proteins (and enzymes) and it is
involved in photosynthesis, eutrophication, acidification and various oxidation-reduction processes.
Through these processes, N changes in form (compounds), reactivity and mobility. Main mobile forms
are the gaseous forms di-nitrogen (N2), ammonia (NH3), nitrogen oxides (NO and NO2), and nitrous
oxide (N2O), and the water soluble forms nitrate (NO3-), ammonium (NH4
+) and dissolved organically
bound N (DON). In organic matter, most N is in the form of amides, linked to organic carbon (R-NH2).
Because of the mobility in both air and water, N is called “double mobile”.
Integrated nitrogen management emphasizes the need to manage nitrogen in an integrated manner.
The notion that N needs to be managed in a comprehensive and integrated way follows from the
understanding that reactive nitrogen (Nr) once formed is involved in a sequence of transfers,
transformations and environmental effects (e.g., J. N. Galloway et al., 2008; James N. Galloway &
Cowling, 2002), that the economic costs of emissions abatement are often high, and that the
management of a single source and/or a single Nr species, especially agriculture, is not always efficient,
and that nitrogen management also affects the cycling of other elements, including carbon (C),
phosphorus (P) and sulphur (S). Fundamental arguments for using integrated approaches to N
management follow also from the first and second law of thermodynamics. Basically, the first law
implies that the element N can be transformed into different species, but it cannot be ‘destroyed’. The
second law of thermodynamics basically implies that N has the natural tendency ‘to dissipate’ into the
environment. Nitrogen has been termed ‘double mobile’, together with carbon and sulfur (Smil, 2001),
because these elements are mobile in both air and water (and soil).
Though there is scientifically sound underpinning for considering the management of the various N
sources in a more holistic and integrated manner, there are also barriers and constraints for more
integrated approaches, such as the compartmental and discipline oriented structure and organization of
policy departments and science groups. There is also discussion about ‘what and how to integrate?’ In
EU policy, there is an increasing tendency for developing more integrated (economic-environmental)
approaches, but many current environmental policies still have a narrow scope as regards N
management. The discussion is in part also confused by lack of clear and accepted definitions about
the terms ‘integrated’ and ‘management’. Integration is perceived as combining separate elements and
aspects in an organized way, so that the constituent units function cooperatively. There are various
integrated approaches to N management in practice, with various degrees of combining separate
elements and aspects. There are at least 5 different dimensions of integration in N management, namely:
(i) vertical integration, (ii) horizontal integration, (iii) integration of other elements, (iv) integration of
stakeholders’ views, and (v) regional integration.
Box 1. Nitrogen is essential for life but too much nitrogen is harmful
Nutrient elements are essential resources for food, feed and biofuel production, next to energy, carbon dioxide,
water, biodiversity, labour, capital and management. Plants require 14 nutrient elements, in specific amounts, for
proper growth and development. Animals and humans require some 22 nutrient elements in specific quantities,
for proper growth and development.
Nitrogen (N) is a main nutrient element and needed in relatively large quantities for the production of amino acids
(protein), nucleic acids and chlorophyll in plants. Nitrogen occurs in different forms in soil, air and waters, but
only a few N forms are directly available for uptake by plant roots. The availability of N often limits food, feed
and biofuel yields, and is one of the elements that is most limiting biomass production in the world.
The invention of the Haber-Bosch process, more than 100 yrs ago, marks a major change in the global N cycle,
as it allowed the large-scale production of synthetically produced N fertilizers from di-nitrogen (N2) in the
atmosphere. Relatively cheap N fertilizers came on the market from about the 2nd half of the 20th century,
especially in affluent countries. The increased use of N fertilizers has contributed greatly to the increased global
food, feed and biofuel production, needed for the increasing human and animal populations (Smil, 2000).
Global N fertilizer use has increased from about 10 Tg in 1961 to almost 110 Tg in 2012 (Figure 1), but there are
large differences between continents. Fertilizer N use in Africa is staggering at a level of about 1-2 Tg per year
during the last decade, while fertilizer N use in Asia has increased during last three decades by an average 2 Tg
per year. Fertilizer N use in Europe increased fast between 1950 and 1990, but stabilized thereafter at a level of
about 10 Tg per year (Sutton et al., 2013, 2011). The apid decrease in European N use around 1990 is mainly due
to the political restructuring of Eastern and Central Europe at this time. The slow decrease in fertilizer use in
Europe between 1990-2010 is related also to EU agri-environmental policy.
Box 1 Figure 1. Changes in Fertilizer N, P, K use in the world and Europe during 1961-2011 (FAOSTAT, 2015)
The availability of N in agriculture increased during the last 100 yrs also through the production of leguminous
crops (beans, pulses, clover and alfalfa) that fix N2 biologically, through energy combustion that increases
atmospheric NOx emissions and N deposition, and through the increasing production of animal manures, and of
residues and wastes from industries and households (Herridge et al., 2008; Sutton et al., 2013).
The increased availability of N in agriculture has also increased the losses of N to the wider environment, to air
and water bodies. Emissions of N to the wider environment occur via various N forms (Box 2; e.g., NH3, N2, N2O,
NO, NO3-), which can lead to problems related to human health and ecosystem degradation. The volatilization of
ammonia (NH3), leaching of nitrate (NO3-), and the emissions of di-nitrogen (N2), nitrous oxide (N2O) and
nitrogen oxide (NO) following nitrification-denitrification reactions are the main N loss pathways from
agricultural systems and food systems. These N forms (except N2) are often termed “reactive N”, as they are
biologically, photo-chemically and/or radiatively active N compounds. Possible human health and environmental
effects of this reactive N include (Galloway et al., 2008; Sutton et al., 2013) a decrease of human health, due to
NH3 and NOx induced formation of particle matter (PM2.5) and smog, plant damage through NH3 and through NOx
induced tropospheric ozone formation; a decrease of species diversity in natural areas due to deposition of NH3
and NOx; acidification of soils because of deposition of NH3 and NOx; pollution of groundwater and drinking
water due to nitrate leaching; eutrophication of surface waters, leading to algal blooms and a decrease in species
diversity; global warming because of emission of N2O; and stratospheric ozone destruction due to N2O.
0
20
40
60
80
100
120
1961 1971 1981 1991 2001 2011
Tg n
utr
ien
t/yr
Global
N
P
K
0
4
8
12
16
1961 1971 1981 1991 2001 2011
Tg
nu
trie
nt/
yr
Europe
Box 2. The Nitrogen Cycle
Nitrogen (N) occurs in different forms and transforms from one form into the other almost endlessly (Figure 2).
Molecular nitrogen (N2) is the dominant constituent of our atmosphere and the most abundant N form on Earth.
Only a few microorganisms have the capability to utilize (fix) N2, converting it to organically bound N. The
Haber-Bosch process converts N2 into ammonia/ammonium (NH3/NH4+) in a physical-chemical manner. The
NH3/NH4+ can be taken up by plants (assimilation). Following the senescence of plants and organisms, the
organic-N is transformed again into NH3/NH4+ (through mineralization). Autotrophic bacteria can utilize the
energy contained in NH3/NH4+ through nitrification. Thereby, the oxidation status increases from -3 in NH3/NH4
+
to +5 in nitrate (NO3-). The NO3
- can be taken up by plants (assimilation) or it is denitrified to nitrous oxide (N2O)
and to di-nitrogen (N2) in anaerobic environments through heterotrophic bacteria. Molecular N (N2) may be
formed also through anaerobic ammonium oxidation (anammox; NH4+ + NO2
- → N2 + 2H2O), by
chemoautotrophic bacteria in the deep sea.
Box 2, Figure 2. presents a quantitative picture of the global N cycle. Large amounts of N cycle between
atmosphere and the terrestrial and marine biospheres, via gaseous N forms. The N cycle is strongly linked with
the carbon cycle and with other nutrient cycles, including phosphorus (P), and sulphur (S); managing N affects
also the cycling of C, P, and S and the net release of CO2 into the atmosphere and C sequestration in soils.
Box 2 Figure 1. Processes of the N
cycle and the related changes in the
oxidation status of the N forms. The
oxidation status (vertical axis) ranges
from +5 in nitrate (NO3-) to +3 in nitrite
(NO2-), to +2 in nitrogen oxide (NO), to
+1 in nitrous oxide (N2O), to 0 in di-
nitrogen (N2), and -3 in ammonia
(NH3), ammonium (NH4+) and amines
(C-NH2). The N forms NH3, N2, N2O,
NO, NOX are gaseous at temperature at
the earth surface; the N forms NO3- and
NH4+ and some organic N forms (DON)
are readily soluble in water. This makes
N ‘double mobile’ (Smil, 2000).
Box 2 Figure 2. Global nitrogen cycle,
showing the dominant flows of N
between atmosphere and the natural
terrestrial area, the anthropogenic area
(agricultural + industrial + urban), and
the marine area. Arrows indicate the
approximate size of the N flows, in Tg
N per yr. Numbers in boxes refer to the
size of the N pool of that compartment,
in Tg N. Note that the transport of N
from anthropogenic sources to the
natural terrestrial and marine areas
occurs mainly via the atmosphere and
rivers. The magnitude of some flows are
rather uncertain. Compilation of data
from (Fowler et al., 2013; Schlesinger
and Bernhardt, 2013; Smil, 2000).
1.2 Dimensions of integration
1.2.1 Vertical integration
Vertical integration in economy is the linkage of upstream suppliers to downstream buyers (Figure 1).
Vertical integration results in more control, higher production efficiency and more marketing power.
Vertical integration in ecology is the functional linkage of autotrophic producers to heterotrophic
consumers (including herbivores, carnivores, omnivores and saprovores), expressed in the idea of a
food chain. In terms of N management, vertical integration relates to linking ‘cause and effect’, and
‘source and impact’. Examples of vertical integration are the ‘driving forces, pressures, state, impact
and response’ framework (DPSIR-framework; see EEA, 1995; OECD, 1991) and the ‘effects-based
approach’ to emissions abatement policies as applied in the Gothenburg Protocol (UNECE, 1991).
Essentially, vertical integration is the basis of all current N policies in Europe, as the human health
effects and ecological impacts are the legitimate of these policies, while the selection of abatement
measures is based in part on the economic consequences (cost-effectiveness). Thus, the gains in human
health and biodiversity are weighted against the cost of the emission abatement. A full cost-benefit
analysis is still complicated, because of the difficulty of attaching monetary values to human health and
ecosystems, although significant progress has been made (ten Brink et al., 1991). Evidently, including
cost-benefit analyses would make vertical integration of N management more complete.
Figure 1. Conceptual visualization of vertical and horizontal integration of firms in production chains (Oenema et al.,
2011).
1.2.2 Horizontal organization
Horizontal organization is related to up-scaling so as to benefit from larger scale and number. Horizontal
integration is the linkage of elements of similar entity, for example when similar firms merge to benefit
from the economics of scale (Figure 1). Also the herding of animals, schooling of fishes, flocking of
birds and colonies of ants and termites can be considered as forms of horizontal integration. Horizontal
integration in N management relates to combining N species, N sources and N emissions within a certain
Production chain Production chain
Retail
Wholesale
ProcessingVERTICAL
INTEGRATIONManufacturer b
Manufacturer a
Suppliers
HORIZONTAL INTEGRATION
area in the management plan. Partial forms of horizontal integration are in the Gothenburg Protocol
(e.g., all anthropogenic NOx sources and all NH3 sources have been included, but N2O emissions to air
and N leaching to waters are not included) and the EU Nitrates Directive (all N sources in agriculture
have to be considered for reducing NO3 leaching to waters, but NH3 and N2O emissions to air are not
addressed explicitly). Similarly, the emission of gaseous N2 through denitrification is not considered in
these policies. Although emission of gaseous N2 does not lead directly to adverse environmental effects,
its release can be considered as a waste of the energy used to produce Nr, indicating the need that N2
emissions should also be addressed.
Conceptually, the N cascade model (Erisman et al., 2011; Galloway et al., 2003) is a nice example of
horizontal integration, but this model has not been made operational for management actions yet. The
N cascade is also a conceptual model for vertical integration, especially when cost-benefit analyses are
included.
1.2.3 Integration of other elements and compounds
Emissions of NOx, NH3 and sulphur dioxide (SO2) to air have rather similar environmental effects (air
pollution, acidification, eutrophication), and that is the reason that the effects-based approach of the
CLRTAP Gothenburg Protocol and the EU National Emission Ceiling Directive address each of NOx,
NH3 and SO2. Similarly, emissions of Nr and phosphorus (P) to surface waters both contribute to
eutrophication and biodiversity loss, and thus EU policies related to combat eutrophication of surface
waters address N and P simultaneously (Oenema et al., 2011). Further, the N and carbon (C) cycles in
the biosphere are intimately linked, and the perturbations of these cycles contribute to increased
emissions of CO2, CH4 and N2O to the atmosphere. Climate change policies address these greenhouse
gases simultaneously. Nitrogen may also affect CO2 emissions through its effect on carbon
sequestration in the biosphere and by alteration of atmospheric chemistry (Butterbach-Bahl et al., 2011).
Evidently, there are two main reasons to integrate N management with the management of specific other
elements (compounds) in environmental policy, namely (i) the other elements (compounds) have
similar environmental effects, and (ii) interactions between N species and these other elements and
compounds. From the practitioner point of view, there can be benefits when managing N and specific
other elements simultaneously. This holds for example for NOx and SO2 (and soot) from combustion
sources, and N and P in agriculture and sewage waste treatment.
1.2.4 Stakeholder involvement and integration
Any N management policy, whether integrated or not, needs to be: (i) policy-relevant; i.e., address the
key environmental and other issues; (ii) scientifically and analytically sound; (iii) cost effective; i.e.,
costs have to be in proportion to the value of environmental improvement, and (iv) politically legitimate;
i.e., acceptable and fair to users. When one or more of these constraints are not fulfilled, the
management policy will be less effective, either through a delay in implementation and/or through poor
implementation and performance. Satisfying the aforementioned constraints requires communication
between actors from policy, science and practice. Tuinstra, Hordijk, & Kroeze (2006) argue that the
credibility, legitimacy and relevance of the science-policy interaction are to a large extent determined
by ‘boundary’ work in an early stage of the communication process between policy and science. They
analyzed the communication process between policy and science in the Convention for Long-range
Transboundary Air Pollution (CLRTAP) and the EU National Emission Ceiling Directive. Boundary
work is defined here as the practice of maintaining and withdrawing boundaries between science and
policy, thereby shaping and reshaping the science-policy interface.
Of similar importance is the communication with practitioners, i.e., the actors that ultimately have to
execute management actions in practice. Integrating their views has to be done also as early as possible
during the design phase of the N management plans and measures, because the practitioners, in the end,
have to implement the management measures. Integrating views of practitioners may range from public
consultation procedures, hearings to participatory approaches and learning; the latter take the
practitioners’ perspectives fully into account and give them a say also in planning and managing. A
good example of the latter approach is the EU Water Framework Directive (EU, 2000), which requires
full stakeholder involvement for the establishment of water basin management plans.
Integration of practitioners’ views does not necessarily lead to faster decision making; on the contrary,
the decision making process often takes more time. Public consultation procedures can be very long-
winded, though techniques like multi-criteria decision making (MCDM) may support decision making
effectively; this approach aims at deriving a way out of conflicts and to come to a compromise in a
transparent process. Integration of practitioners’ views may ultimately improve the acceptance of the
management strategies, and thereby facilitate the implementation of the management strategies in
practice.
1.2.5 Regional integration
Regional integration or ‘integration of spatial scales’ is considered here as the fifth dimension of
integration. Regional integration aims at enhanced cooperation between regions. It relates to integration
of markets and to harmonization of governmental polices and institutions between regions through
political agreements, covenants and treaties (Bull et al., 2011). Arguments for regional integration are:
(i) enhancing markets, (ii) creation of a level-playing field, (iii) the transboundary nature of
environmental pollutions and (iv) the increased effectiveness and efficiency of regional policies and
related management measures.
In terms of N management, regional integration relates, for example, to the harmonization and
standardization of environmental policies across European Union and for air pollution in the UNECE
region (Bull et al., 2011; Oenema et al., 2011). The water basin or catchment management plans
developed within the framework of the EU Water Framework Directive are also a form of regional
integration. Here, water quantity and quality aspects are considered in an integrated way for a well-
defined catchment.
The trend toward regional integration during last decades does not necessarily mean that local
management actions are less effective and/or efficient. Local actions can be made site-specific and, as
a consequence, are often more effective than generic measures. This holds both for households, farms
and firms, and especially when actors can have influence on the choice of actions. Also, the motivation
for contributing to the local environment and nature can be larger than for contributing to the
improvement of the environment in general (e.g., Kahn, 2001);
1.3 Tools for integrated approaches to N management
The toolbox for developing integrated approaches to N management contains tools that are uniformly
applicable, as well as highly specific, suitable for just one dimension of integration. Important common
tools are: (i) systems analysis, (ii) communication, (iii) N budgeting, (iv) integrated assessment
modeling and cost-benefit analyses, (v) logistics and chain management, and (vi) stakeholder dialogue.
The starting point for developing integrated approaches is ‘systems analysis’, as it provides information
that is needed for all dimensions of integration. Systems analysis allows for identifying and quantifying
components, processes, flows, actors, interactions and inter-linkages within and between systems, and
provides a practical tool for discussing integrated approaches to N management. In essence, it
encompasses the view that changes in one component will promote changes in all of the components of
the systems (e.g., Odum, 1996). These type of tools are being used especially by the science-policy
interface.
A second tool for developing integrated approaches is communication. Communication is transferring
information, but at the same time the tool for raising awareness and for explaining the meaning, purpose,
targets and actions of integrated approaches to N management to all actors involved. Clear
communication is important, as there is often ambiguity in the use of the terms ‘integrated’ and
‘management’ and insufficient clarity about the objectives and required actions. Communication can
help make the concept transparent and thereby can facilitate the adoption of targets and measures in
practice.
Figure 2. Concept of the nitrogen input – output mass balance of mixed crop – livestock production systems. The ‘hole
of the pipe’ model illustrates the ‘leaky N cycle’ of crop and animal production; it shows the fate of N inputs in
agriculture. Inputs, outputs in useful products and emissions to air and water show dependency in crop production
and animal production; a change in the flow rate of one N flow has consequences for others, depending also on the
storage capacity of the system. Total inputs must balance total outputs, following corrections for possible changes in
storage within the system (Oenema et al., 2009)
1.3.1 Nitrogen balances
A third type of tool is nitrogen balances, which quantifies the differences between nitrogen inputs and
outputs of systems and of the compartments of these systems. This is an indispensible tool for horizontal
integration and in part also vertical integration; it integrates over N sources and N species for well-
defined areas and/or components. The N balance records all inputs all outputs in marketed products,
and the N surplus, the difference between total inputs and total output. The ‘hole-in-the-pipe model’
illustrates the leaky nature of the agricultural and food systems, i.e., there are many opportunities for N
species to escape (Error! Reference source not found.). The hole-in-the-pipe model also illustrates
the importance of integrated N management; i.e., mitigation of an N loss pathway will inevitably
increase other N loss pathways (i.e., pollution swapping), unless the total output in harvested product
is increased and/or the total N input decreased proportionally. Input-output balances can help to detect
and illustrate pollution swapping. Input-output N balances have been proven to be easy-to-understand
management tools for farmers (Jarvis et al., 2011), plant managers and policy managers (see
supplementary information to this chapter). Input-output balances and budgets are flexible tools, but
require uniform definitions and conventions to circumvent bias (Leip et al., 2011; Oenema et al., 2003).
Life Cycle Assessment (LCA) is an approach to account for emissions and resources during the entire
life cycle of a product. It can be seen also as a tool for horizontal integration, similar as input-output
budgets, but it integrates also over time. This type of tool is especially used by scientists, while also
being relevant for use by practitioners.
1.3.2 Integrated assessment modeling
A fourth type of tool is integrated assessment modeling, including ecological food print analyses, cost-
benefit analyses and target setting. These tools are indispensible for vertical integration, relating cause
and effect to impact, and analyzing the responses by society (actors). The ‘DPSIR model’ is a
conceptual tool for analyzing cause-effect relationships. It relates Driving forces of environmental
change (population growth, economic growth, etc.), to Pressures on the environment (e.g., Nr
emissions), to State of the environment (e.g., water quality), to Impacts on population, economy and
ecosystems, and finally to the Response of the society (EEA, 1995; OECD, 1991). Integrated
assessment modelling is the interdisciplinary process that quantifies and analyzes these cause-effect
relationships in the current situation (using empirical data and information) and for future conditions
(using scenario analyses), in order to facilitate the framing of strategies. Examples include reviews of
the Gothenburg Protocol by the Taskforce on Integrated Assessment Modelling of the UNECE
Convention on Long-range Transboundary Air Pollution (TFIAM/CIAM, 2006). Cost-Benefit Analysis
(CBA) go a step further by expressing costs and benefits of policy measures in monetary terms.
However, attaching financial values to, for example, improvement of human health and increased
ecosystem protection is not without its challenges (ten Brink et al., 1991). This type of tool is generally
applied at the science-policy interface. They are also used to assess uncertainties in the cause-effect
relationships and in the effects of management measures.
1.3.3 Logistics and chain management
A fifth tool for integrated approaches to N management is ‘logistics and chain management’. This is
the planning and management of activities, information and N sources in firms, installations and
departments between the point of origin and the point of consumption. In essence, logistics and chain
management integrate the supply and demand within and across companies. Logistics and chain
management is especially important for N fertilizer producing companies, animal feed companies,
transport and distribution sectors, processing industries, companies involved in recycling (sewage
waste, composts, etc.), but also large farms. This type of tool is used especially by practitioners.
1.3.4 Stakeholder dialogue
A sixth type of tool is stakeholder dialogue, including Multi Criteria Decision Analysis (MCDA),
learning and participatory approaches. Evidently, this type of tool is indispensible for addressing the
views of actors in N management issues (the 4th dimension of integration). The intention of stakeholder
dialogue is to get people from different perspectives to enter a result-oriented conversation. Stakeholder
dialogue is interaction between different stakeholders to address specific problems related to competing
interests and competing views on how N and other resources should be used and managed. Rotmans
(2003) describes the roles of stakeholders, networking, and self-governance in transition management.
MCDA has been used in the water quality context and also in setting strategies for NH3 control in a
wider context (including dietary change). It is a good way of involving different stakeholder interests
and for dealing with uncertainties.
Further, high-level meetings and resulting treaties are seen as a tool to achieve regional integration of
N management measures. Regional integration is the most complex and encompassing way of
integration. Also, there are many ways for and stages of regional integration, with not just one most
superior outcome (in terms of ratification, exemptions, delayed implementation, etc.). This offers the
opportunity of creating flexibility (Bull et al., 2011).
Finally, integrated approaches to N management can be expected to have different policy targets than
policies oriented toward single N sources and N species. Based in part on the critical-load concept and
emission ceilings for N species developed under the CLRTAP Gothenburg Protocol, it is suggested that
incentive-based N budgets and Nr ceilings per area, sector and or activity could be useful indicators,
because they integrate multiple elements of N effects in the environment. The usefulness and analytical
soundness of such indicators have to be further explored.
1.4 Elements of integrated nitrogen management
Management is often called the “fourth production factor”, in addition to land, labour and capital
(techniques). Its importance for the economic and environmental performance of agricultural is
enormous. Management is commonly defined as “a coherent set of activities to achieve objectives”.
Nitrogen management can be defined as “a coherent set of activities related to the handling and
allocation of N on farms to achieve agronomic and environmental/ecological objectives” (e.g., Oene
Oenema & Pietrzak, 2002). The agronomic objectives relate to crop yield and quality, and animal
performance in the context of animal welfare. The environmental/ecological objectives relate to
minimizing N losses from agriculture. “Taking account of the whole N cycle” emphasizes the need to
consider all aspects of N cycling and all possible N lossses, to circumvent “pollution swapping”.
Nitrogen management can be considered as the “software” and “org-ware”, while the techniques may
be considered as the “hardware” of N emissions abatement. Hence, N management has to be considered
in conjunction with the techniques used.
1.4.1 Integrated management pracitices
Depending on the type of farming systems, N management at farm level involves a series of
management activities in an integrated way, including:
(a) Fertilization of crops;
(b) Crop growth, harvest and residue management;
(c) Growth of catch or cover crops;
(d) Grassland management;
(e) Soil cultivation, drainage and irrigation;
(f) Animal feeding;
(g) Herd management (including welfare considerations), including animal housing;
(h) Manure management, including manure storage and application;
(i) Ammonia emission abatement measures;
(j) Nitrate leaching and run-off abatement measures;
(k) N2O emission abatement measures;
(l) Denitrification abatement measures.
To be able to achieve high crop and animal production with minimal N losses and other unintended
environmental consequences, all activities have to be considered in an integrated and balanced way.
Nitrogen is often the most limiting nutrient, and therefore must be available in sufficient amount and in
a plant-available form in soil to achieve optimum crop yields. Excess and/or untimely N applications
are the main source of N losses to the environment. To avoid excess or untimely N applications is one
of the best ways to minimize N losses, while not affecting crop and animal production. Guidelines for
site-specific best nutrient management practices should be adhered to, including:
(a) Nutrient management planning and record keeping, for all essential nutrients;
(b) Calculation of the total N requirement by the crop on the basis of realistic estimates of
yield goals, N content in the crop and N uptake efficiency by the crop;
(c) Estimation of the total N supply from indigenous sources, using accredited methods:
(i) Mineral N in the upper soil layers at planting and in-crop stages (by
soil and/or plant tests);
(ii) Mineralization of residues of the previous crops;
(iii) Net mineralization of soil organic matter, including the residual effects
of livestock manures applied over several years and, on pastures,
droppings from grazing animals;
(iv) Deposition of reactive N from the atmosphere;
(v) Biological N2 fixation by leguminous plants;
(d) Computation of the needed N application, taking account of the N requirement of the
crop and the supply by indigenous N sources;
(e) Calculation of the amount of nutrients in livestock manure applications that will become
available for crop uptake. The application rate of manure will depend on:
(i) The demands for N, phosphorus and potassium by the crops;
(ii) The supply of N, phosphorus and potassium by the soil, based on soil
tests;
(iii) The availability of livestock manure;
(iv) The immediately available N, phosphorus and potassium contents in
the manure and;
(v) The rate of release of slowly available nutrients from the manure,
including the residual effects;
(f) Estimation of the needed fertilizer N and other nutrients, taking account of the N
requirement of the crop and the supply of N by indigenous sources and livestock
manure;
(g) Application of livestock manure and/or N fertilizer shortly before the onset of rapid
crop growth, using methods and techniques that prevent NH3 emissions;
(h) Where appropriate, application of N fertilizer in multiple portions (split dressings) with
in-crop testing, where appropriate.
The effectiveness of N management can be evaluated in terms of (a) decreases of Nsurplus; and (b)
increases of N use efficiency. NUE indicators provide a measure for the amount of N that is retained in
crop or animal products, relative to the amount of N applied or supplied. Nsurplus is an indicator for
the N pressure of the farm on the wider environment, also depending on the pathway through which
surplus N is lost, either as NH3 volatilization, N leaching and/or nitrification/denitrification.
Management has a large effect on both NUE (Tamminga 1996; Mosier, Syers and Freney, 2004) and
Nsurplus.
While the ratio of total N output (via products exported from the farm) and total N input (imported into
the farm, including via biological N2 fixation) (mass/mass ratios) is an indicator for the NUE at farm
level, the total N input minus the total N output (mass per unit surface area) is an indicator of the
Nsurplus (or deficit) at farm level.
There are various procedures for making N input-output balances, including the gross N balance, the
soil-surface balance, the farm-gate balance, and the farm balance (OECD, 2008; Schröder et al., 2004;
Van Beek et al., 2003; Watson and Atkinson, 1999). Basically, the gross N balance and the soil-surface
balance record all N inputs to agricultural land and all N outputs in harvested crop products from
agricultural land. However, the balances differ in the way they account for the N in animal manure; the
gross N balance includes the total amount of N excreted as an N input item, while the soil-surface
balance corrects the amount of N excreted for NH3 losses from manure in housing systems and manure
storage systems. The farm-gate balance and the farm balance records all N inputs and all N outputs of
the farm; the farm balance includes N inputs via atmospheric deposition (both reduced and oxidized N
compounds) and biological N2 fixation. Various methods can be applied at the field, farm, regional and
country levels; it is important to use standardized formats for making balances and to report on the
methodology so as to improve comparability.
1.4.2 Farm Nitrogen Budgets
A farm N budget details all N inputs and outputs and including losses (Figure 3). The main inputs are
mineral/inorganic fertilizer, imported animal manure, fixation of atmospheric N2 by some (mainly
leguminous) crops, deposition from the atmosphere, inputs from irrigation water and livestock feed.
Inputs in seed and bedding used for animals are generally minor inputs, although the latter can be
significant for some traditional animal husbandry systems. The main outputs are in crop and animal
products, and in exported manure. Gaseous losses occur from manure in animal housing, in manure
storage and after field application. Other gaseous losses occur from fields; from applied fertilizer, crops,
soil and crop residues. Losses to groundwater and surface water occur via leaching or run-off of nitrates,
ammonium and DON. Run-off of undissolved organic N may also occur.
Figure 3. A farm N budget of a mixed crop-animal production farm (Jarvis et al., 2011)
The farm N balance is simpler than a farm N budget, as the N losses are not detailed. The farm N
balance details all N inputs and harvested N outputs (hence no N losses), as well as the balance, i.e., the
difference between total N input and total N output.
A soil surface N balance of agricultural land is shown in Figure 4. The main N inputs are
mineral/inorganic fertilizer, animal manure, fixation of atmospheric N by leguminous crops, and
deposition from the atmosphere. Other N inputs may include bio-solids, and organic amendments like
compost and mulches. Inputs in seed and composts are generally minor inputs. The main outputs are in
harvested crop products, which may be the grain or the whole crop. Note that animal products other
than animal manure do not show up in the soil surface balance, as they are not placed onto the soil
surface.
For using N balances and NUE as indicators at farm level, a distinction has to be made between:
(a) Specialized crop production farms;
(b) Mixed crop (feed)-animal production farms;
(c) Specialized animal production farms.
Specialized crop production farms have relatively few NH3 emission sources (possibly imported animal
manure, urea and ammonium-based fertilizers, crops and residues). These farms can be subdivided
according to crop rotation (e.g., percentage of cereals, pulses, vegetables and root crops). Specialized
animal production farms produce only animal products (milk, meat, egg, animal by-products and animal
manure) and all these products are exported from the farm. Energy may also be produced through
digestion of organic carbon. These farms can be subdivided according to animal categories (e.g., pig,
poultry, and cattle). Mixed systems have both crops and animals; the crops produced are usually fed to
the animals, while the manure produced by the animals is applied to the cropland. These farms can be
subdivided according animal categories (e.g., dairy cattle, beef cattle, pigs, etc.) and livestock density
(or feed self-sufficiency).
The variation between farms in NUE (output/input ratios) and Nsurpluses (input minus output) is large
in practice, due to the differences in management and farming systems (especially as regards the types
of crops and animals, the livestock density and the farming system). Indicative ranges can be given for
broad categories of farming systems (see Table 1).
Inorganic N
fertilizers
Agricultural land
Animal
manure
Biological
N2 fixation
Atmospheric
N deposition
Seeds &
plantsComposts
Harvested crop
products
Grass and
fodder products
N balance(N Surplus)
N inputs
N outputs
Inorganic N
fertilizers
Agricultural land
Animal
manure
Biological
N2 fixation
Atmospheric
N deposition
Seeds &
plantsComposts
Harvested crop
products
Grass and
fodder products
N balance(N Surplus)
N inputs
N outputs
Figure 4. Components of a soil surface N balance of agricultural land. (OECD, 2008)
Table 1. Nsurplus and NUE indicators of farming systems, with typical values for specialized crop production farms,
specialized animal production farms and mixed farms
Index Calculation Interpretation Typical levels
Nsurplus = sum of
all N inputs minus
the N outputs that
pass the farm gate,
expressed in
kg/ha/yr
N surplus =
Σ (InputsN) –
Σ (outputsN)
Nsurplus depends on the types of farming
system, crops and animals, and indigenous N
supply, external inputs (via fertilizers and
animal feed) management and environment
Nsurplus is a measure of the total N loss to
the environment
N deficit [Σ (InputsN) < Σ (outputsN] is a
measure of soil N depletion
For specialized animal farming systems
(landless), the Nsurplus can be very large,
depending also on the possible N output via
manure processing and export
Depends on types of
farming systems,
crops and animals:
Crop: 0–50 kg/ha
Mixed: 0–200 kg/ha
Animal: 0–1,000
kg/ha
NUE = N use
efficiency, i.e., the
N output in useful
products divided by
the total N input
NUE =
Σ (outputsN) /
Σ (InputsN)
NUE depends on types of farming system,
crops and animals, and indigenous N supply,
external inputs (via fertilizers and animal
feed) management and environment
For specialized animal farming systems
(landless), there may be N output via manure
export.
Depends on types of
farming systems,
crops and animals:
Crop 0.6–1.0
Mixed: 0.5–0.6
Animal 0.2–0.6a
Animal 0.8–0.95b
a No manure export. b Landless farms; all manure exported off-farm.
Nitrogen balances and N output-input ratios can be made also for compartments within a farm,
especially within a mixed farming system. For estimating NUE, three useful compartments or levels
can be considered:
(a) Feed N conversion into animal products (feed-NUE or animal-NUE);
(b) Manure and fertilizer N conversion into crops (manure/fertilizer-NUE);
(c) Whole-farm NUE.
These NUEs are calculated as the percentage mass of N output per mass of N input:
(a) Feed-NUE = [(N in milk, animals and eggs) / (N in feed and fodder)] x 100%;
(b) Manure/fertilizer-NUE = [N uptake by crops / N applied as manure/fertilizer] x 100%;
(c) Whole-farm NUE = [Σ(N exported off-farm) / Σ(N imported on to the farm)] x 100%.
Nitrogen management is based on the premise that decreasing the nitrogen surplus (Nsurplus) and
increasing N use efficiency contributes to the mitigation of N losses via NH3 emissions, nitrate leaching
and denitrification. Nitrogen management also aims to identify and prevent pollution swapping
between different N compounds and environmental compartments. Establishing an N input-output
balance at the farm level is a prerequisite for optimizing N management in an integral way. Table 2
lists indicative ranges for N use efficiency (NUE) and the Nsurplus of the input-output balance of
different farming systems. These ranges serve as rough guidance; they can be made more farm and
country specific. Nitrogen use efficiency should be managed in concert with overall nutrient efficiencies
and other factors, such as pest control.
Table 2. Indicative ranges for target N surplus and NUE as a function of farming system, crops
Farming systems Species/
categories
NUE
(kg/kg)
Nsurplu
s
(kg/ha/y
r) Comments
Specialized cropping
systems
Arable crops 0.6–0.9 0–50 Cereals have high, root crops low, NUE
Vegetables 0.4–0.8 50–100 Leafy vegetables have low NUE
Fruits 0.6–0.9 0–50
Grassland-based
ruminant systems
Dairy cattle 0.3–0.5 100–150 High milk yield, high NUE; low
stocking density, low Nsurplus
Beef cattle 0.2–0.4 50–150 Veal production, high NUE; 2-year-old
beef cattle, low NUE
Sheep and goats 0.2–0.3 50–150
Mixed crop-animal
systems
Dairy cattle 0.4–0.6 50–150 High milk yield, high NUE; concentrate
feeding, high NUE
Beef cattle 0.3–0.5 50–150
Pigs 0.3–0.6 50–150
Poultry 0.3–0.6 50–150
Other animals 0.3–0.6 50–150
Landless systems Dairy cattle 0.8–0.9 n.a.a N Output via milk, animals, manure +
N-loss ~equals N input; Nsurplus is
gaseous N losses from housing and
storage
Beef cattle 0.8–0.9 n.a.a
Pigs 0.7–0.9 n.a.a
Farming systems Species/
categories
NUE
(kg/kg)
Nsurplu
s
(kg/ha/y
r) Comments
Poultry 0.6–0.9 n.a.a
Other animals 0.7–0.9 n.a.a
a Not applicable, as these farms have essentially no land. However, the Nsurplus can be expressed in kg per farm per year. In
the case that all animal products, including animal manure and all residues and wastes, are exported, the target Nsurplus can
be between 0 and 1,000 kg per farm per year, depending on farm size and gaseous N losses.
1.5 Measures to prevent and abate ammonia emissions
The Guidance document on preventing and abating ammonia emissions from agricultural sources lists
8 NH3 emission abatement measures in the following areas:
(a) Nitrogen (N) management, taking into account the whole N cycle;
(b) Livestock feeding strategies;
(c) Animal housing techniques;
(d) Manure storage techniques;
(e) Manure application techniques;
(f) Fertilizer application techniques;
(g) Other measures related to agricultural N;
(h) Measures related to non-agricultural and stationary sources.
These measures are briefly summarized below.
1.5.1 Livestock feeding strategies
Livestock feeding strategies decrease NH3 emissions from manure in both housing and storage, and
following application to land. Livestock feeding strategies are more difficult to apply to grazing
animals, but emissions from pastures are low and grazing itself is essentially a category 1 measure
(category 1 measures are defined as measures that are well researched, considered to be practical or
potentially practical, and have quantitative data on their abatement efficiency, at least at the
experimental scale). Livestock feeding strategies are implemented through (a) phase feeding, (b) low-
protein feeding, with or without supplementation of specific synthetic amino acids and ruminal by-pass
protein, (c) increasing the non-starch polysaccharide content of the feed, and (d) supplementation of
pH-lowering substances, such as benzoic acid. Phase feeding is an effective and economically attractive
measure even if one that requires additional installations. Young animals and high-productive animals
require more protein concentration than older, less-productive animals. Combined NH3 emissions for
all farm sources decrease roughly by 10% when mean protein content decreases by 10 grams (g) per kg
(1%) in the diet. The economic cost of the livestock feeding strategies depends on the cost of the feed
ingredients and the possibilities of adjusting these ingredients, based on availability, to optimal
proportions. The reference here is the mean current practice, which varies considerably across countries
and over time. The net costs of livestock feeding strategies depend on the manipulation of the diet and
the changes in animal performance. In general, high-protein diets and efficient low-protein diets cost
more than diets with medium-high protein contents. Both too high and too low protein contents in the
diet have negative effects on animal performance, although the effects in the latter case are more evident
to producers. The cost of the diet manipulations are in the range of -€10–€10 per 1,000 kg of feed,
depending on market conditions for feed ingredients and the cost of the synthetic amino acids. Hence,
in some years there are benefits while in other years there are costs associated with changes in diets.
Table 3 summarizes possible targets for lowering protein values, maintaining production efficiencies
for each animal category. Note that the economic costs increase as the ambitions to decrease the mean
protein content increase from low to high.
Table 3. Indicative target protein levels (%) of dry feed with a standard dry matter content of 88% for housed animals
as function of animal category and for different ambition levels
Mean crude protein content of the animal feed (%)a
Animal type Low ambition Medium ambition High ambition
Cattle
Dairy cattle, early lactation (> 30 kg/day) 17–18 16–17 15–16
Dairy cattle, early lactation (< 30 kg/day) 16–17 15–16 14–15
Dairy cattle, late lactation 15–16 14–15 12–14
Replacement cattle (young cattle) 14–16 13–14 12–13
Veal 20–22 19–20 17–19
Beef < 3 months 17–18 16–17 15–16
Beef > 6 months 14–15 13–14 12–13
Pigs
Sows, gestation 15–16 14–15 13–14
Sows, lactation 17–18 16–17 15–16
Weaner, <10 kg 21–22 20–21 19–20
Piglet, 10–25 kg 19–20 18–19 17–18
Fattening pig, 25–50 kg 17–18 16–17 15–16
Fattening pig, 50–110 kg 15–16 14–15 13–14
Fattening pigs, >110 kg 13–14 12–13 11–12
Chickens
Chicken, broilers, starter 22–23 21–22 20–21
Chicken, broilers, growers 21–22 20–21 19–20
Chicken, broilers, finishers 20–21 19–20 18–19
Chicken, layers, 18–40 weeks 17–18 16–17 15–16
Chicken, layers, > 40 weeks 16–17 15–16 14–15
Turkeys
Turkeys, < 4 weeks 26–27 25–26 24–25
Mean crude protein content of the animal feed (%)a
Animal type Low ambition Medium ambition High ambition
Turkeys, 5–8 weeks 24–25 23–24 22–23
Turkeys, 9–12 weeks 21–22 20–21 19–20
Turkeys, 13–16 weeks 18–19 17–18 16–17
Turkeys, > 16 weeks 16–17 15–16 14–15
1.5.2 Animal Housing
For animal housing, abating NH3 emissions is based on one or more of the following principles:
(a) Decreasing the surface area fouled by manure;
(b) Rapid removal of urine; rapid separation of faeces and urine;
(c) Decreasing the air velocity and temperature above the manure;
(d) Reducing the pH and temperature of the manure;
(e) Drying manure (especially poultry litter);
(f) Removing (scrubbing) NH3 from exhaust air;
(g) Increasing grazing time.
Different animal categories require different housing systems and environmental conditions, hence
different techniques. Because of their different requirements and housing, there are different provisions
according to animal categories. The references used are the most conventional housing systems, without
techniques for abating NH3 emissions. The costs of techniques used to lower NH3 emissions from
housing are related to: (a) depreciation of investments; (b) economic rent on investments; (c) energy;
and (d) operation and maintenance. In addition to costs, there are benefits related to increasing animal
health and performance. These benefits are difficult to quantify and have not always been included in
the total cost estimate. The economic costs vary because of different techniques/variants and farms
sizes; techniques for cattle housing are still in development. Table 4 presents an overview of the
emission reduction and economic cost for the major animal categories.
Table 4. Ammonia emission reduction techniques for animal housing, their emission reduction levels and associated
costs
Category
Emission reduction
compared with the
reference (%) a
Extra cost (€/kg NH3-N
reduced)
Existing pig and poultry housing on farms
with > 2,000 fattening pigs or > 750 sows
or > 40,000 poultry
20 0–3
New or largely rebuilt cattle housing 0–70 1–20
New or largely rebuilt pig housing 20–90 1–20
New and largely rebuilt broiler housing 20–90 1–15
New and largely rebuilt layer housing 20–90 1–9
New and largely rebuilt animal housing on
farms for animals other than those already
listed in this table
0–90 1–20
1.5.3 Manure Storage
For manure storages, abating NH3 emissions is based on one or more of the following principles: (a)
decreasing the surface area where emissions can take place, i.e., through covering of the storage,
encouraging crusting and increasing the depth of storages; (b) decreasing the source strength of the
emitting surface, i.e., through lowering the pH and ammonium (NH4) concentration; and (c) minimizing
disturbances such as aeration. All principles have been applied in category 1 (i.e., scientifically sound
and practically proven) techniques. These principles are generally applicable to slurry storages and
manure (dung) storage. However, the practical feasibility of implementing the principles are larger for
slurry storages than for manure (dung) storages. The reference here is the uncovered slurry store without
crust and uncovered solid manure heap.
The costs of techniques used to lower NH3 emissions from storages are related to: (a) depreciation of
investments; (b) economic rent on investments; and (c) maintenance. Here, a summary is provided of
the total costs, in terms of euros per kg of ammonia-nitrogen (NH3-N) saved (Table 5). In addition to
costs, there are benefits related to decreased odour emissions, decreased rainwater infiltration and
increased safety (no open pits); some of these benefits are difficult to quantify and therefore have not
been included here. Ranges of costs relate to different techniques/variants and farm size. Note that the
cost of the storage system itself is not included in the cost estimates of Table 5. Some covers can only
be implemented when new storages are built. Manure processing, such as separation, composting and
digestion, have implications for the total losses during “storage”.
Table 5. Ammonia emission reduction techniques for manure storages, their emission reduction levels and associated
costs
Techniques Emission reduction (%) Cost (€ per m3 per year) Cost (€ per kg NH3-N saved)
Tight lid > 80 2–4 1–2.5
Plastic cover > 60 1.5–3 0.5–1.3
Floating cover > 40 1.5–3*) 0.3–5a
a Not including crust; crusts form naturally on some manures and have no cost, but are difficult to predict.
1.5.4 Manure application techniques
Low-emission manure application is based on one or more of the following principles: (a) decreasing
the surface area where emissions can take place, i.e. through band application, injection or
incorporation; (b) decreasing the time that emissions can take place, i.e., through rapid incorporation of
manure into the soil, immediate irrigation or rapid infiltration; and (c) decreasing the source strength of
the emitting surface, i.e., through lowering the pH and NH4 concentration of the manure (through
dilution). All principles have been applied in category 1 (i.e., scientifically sound and practically
proven) techniques. These principles are generally applicable to slurry and solid manure application.
However, abatement techniques are more applicable and effective for slurry than for solid manures. For
solid manure, the most feasible technique is rapid incorporation into the soil and immediate irrigation.
The reference here is the broadcast spreading of slurry and solid manure. A fourth principle, applying
when volatilization potential is low, such as under low temperature and wind conditions, is considered
category 2 because it requires a method of validation. The costs of techniques used to lower NH3
emissions from application are related to: (a) depreciation of investments costs of the applicator; (b)
economic rent on investments; (c) added tractor costs and labour; and (d) operation and maintenance.
Here, a summary is provided of the total costs, in terms of euros per kg NH3-N saved (Table 6). The
co-benefits relate to decreased odour emissions and biodiversity loss, and increased palatability of
herbage, uniformity of application and consistency of crop response to manure. Some of these benefits
are difficult to quantify and therefore have not all been included in the cost estimations. Ranges of costs
relate to the NH4 content of the slurry/manure; the higher the NH4 content, the lower the abatement
cost. Mean costs are likely in the lower half of the range, especially when application is done by
contractors, on large farms or with shared equipment.
Table 6. Ammonia emission reduction techniques for manure application, their emission reduction levels and associated
costs
Manure type Application techniques
Emission
reduction (%)
Cost
(€ per kg NH3-N
saved)
Slurry Injection > 60 -0.5–1.5
Shallow injection > 60 -0.5–1.5
Trailing shoe, > 30 -0.5–1.5
Band application > 30 -0.5–1.5
Dilution > 30 -0.5–1.0
Management systems > 30 0.0–2.0
Direct incorporation following surface
application
> 30 -0.5–2.0
Solid manure Direct incorporation > 30 -0.5–2.0
1.5.5 Fertilizer application techniques
For application of urea- and ammonium-based fertilizers, abating emissions is based on one or more
of the following principles: (a) decreasing the surface area where emissions can take place, i.e., through
band application, injection, incorporation (but note that rapid increase in pH in concentrated bands of
urea, especially where there is high crop residue, may lead to high emissions due to rise in pH); (b)
decreasing the time that emissions can take place, i.e., through rapid incorporation of fertilizers into the
soil or via irrigation; (c) decreasing the source strength of the emitting surface, i.e., through urease
inhibitors, blending and acidifying substances; and (d) a ban on their use (as in the case of ammonium
(bi)carbonate). All principles have been applied in category 1 (i.e., scientifically sound and practically
proven) techniques. The reference here is the broadcast application of the urea- and ammonium-based
fertilizers.
The costs of techniques used to lower NH3 emissions from fertilizers are related to: (a) depreciation of
investment costs of the applicator; (b) economic rent on investments; (c) use of heavier tractors and
more labour time; and (c) maintenance. Here, a summary is provided of the total costs, in terms of euros
per kg NH3-N saved (Table 7). The possible benefits relate to decreased fertilizer costs, decreased
application costs in a combined seeding and fertilizing system and decreased biodiversity loss. These
benefits are difficult to quantify and have not all been included. Ranges of costs relate to the farm size
(economics of scale), soil conditions and climate (high emission reduction in relatively dry conditions).
Mean costs are likely in the lower half of the range when application is done by contractors or low
emitting fertilizers are substituted.
Table 7. Ammonia emission reduction techniques for application of urea- and ammonium-based fertilizers, their
emission reduction levels and associated costs
Fertilizer type Application techniques
Emission
reduction
(%)
Cost
(€ per kg NH3-N
saved)
Urea Injection > 80 -0.5–1
Urease inhibitors > 30 -0.5–2
Incorporation following surface application > 50 -0.5–2
Surface spreading with irrigation > 40 -0.5–1
Ammonium carbonate Ban ~100 -1–2
Ammonium-based fertilizers Injection > 80 0–4
Incorporation following surface application > 50 0–4
Surface spreading with irrigation > 40 0–4
1.6 Measures to decrease the risk of nitrate leaching losses
Water pollution within the context of the Nitrates Directive (EC, 1991), has been defined as “the
discharge, directly or indirectly of nitrogen compounds from agricultural sources into the aquatic
environment, the results of which are such as to cause hazards to human health, harm to the living
resources and to the aquatic ecosystems, damage to amenities or interference with other legitimate uses
of water”. Further, eutrophication has been defined as “the enrichment of water by nitrogen compounds,
causing accelerated growth of algae and higher forms of plant life to produce an undesirable disturbance
to the balance of organisms present in the water and to the quality of the water concerned”. Though the
emphasis is clearly on ‘nitrates from agricultural sources’ in the Nitrates Directive, it is noted that
phosphorus is as well a dominant cause of eutrophication of many surface waters. Hence, phosphorus
compounds from agricultural sources must be considered as well, when dealing with water pollution
and eutrophication within the context of the Nitrates Directive. Moreover the Nitrates Directive forms
integral part of the Water Framework Directive1, which aims to reach good ecological status of waters.
Particularly in intensive agricultural areas, high levels of P concentrations are one of the main obstacles
to reach this goal.
Growing plants require relatively high concentrations of available N and P, and that is why farmers add
N and P to soil, via animal manure, fertilisers, composts, residues and wastes. These additions of N and
P can potentially pollute water. Pollution risks are determined by pedo-climatic conditions and farming
practices. Risks are high when the availabilities of N and P are high under pedo-climatic conditions that
are favourable to leaching and run-off. Conversely, risks are small when the availabilities of N and P
are low and the pedo-climatic conditions are unfavourable to leaching. Vulnerability of water bodies is
also an important factor to consider while assessing risk for water pollution due to leaching and run off
of nutrients.
The actual vulnerability to leaching of a site depends on the pedo-climatic conditions and farming
practices. As pedo-climatic conditions are largely defined by Mother Nature and are not easy to
manipulate, to a certain extent they govern the available options for farming practices for ensuring
environmental protection. Farming practices will hence have to be adjusted to the pedo-climatic
conditions, when the objective is to decrease the risk of water pollution. Recommendations and
regulations directed at the reduction of pollution risks should therefore ideally be tuned to these different
situations. Farming practices refer to the intricate fabric of nutrient management (type and nature of
fertilisers and manure, rate, timing and method of applications) in close connection with the
complementary farm management (e.g. crop type choice, dates of sowing and harvest, drainage and
irrigation, crop rotation, livestock feeding and housing). The above implies that regulations on any
individual aspect should be defined in view of the many other aspects.
1.6.1 The Nitrates Directive
Article 5 of the Nitrates Directive requires Member States to establish Action Programmes, which
should include measures aimed at preventing and reducing the risk of nitrate leaching and run off from
agricultural practices. Action Programmes should include measures listed in Annex III of the Directive
and those prescribed in the Code of Good Agricultural Practice, as listed in Annex II of the Directive,
1 Directive 2000/60/EC
except where they are superseded by the measures of Annex III. The purpose of these measures is to
minimize the risk of water pollution and to promote the use of ‘best farming practices’ (Box 3).
Box 3. Measures referred to in Annexes II and III of the Nitrates Directive
Annexes II and III of the Nitrates Directive set out a list of measures, which have to be included in the
Code of Good Agricultural Practices (Annex II) and the Action Programme (Annex II and III). In
particular, the Action Programmes must contain provisions relating to:
1. periods when the land application of certain types of fertilizer is prohibited or inappropriate;
2. the capacity and construction of storage vessels for livestock manures, including measures to prevent
water pollution by run-off and seepage into the groundwater and surface water of liquids containing
livestock manures and effluents from stored plant materials such as silage;;
3. the land application of fertilizer to steeply sloping ground;
4. the amount of livestock manure applied to the land each year, including by the animals themselves,
which shall not contain more than 170 kg N per hectare.
5. the land application of fertilizer to water-saturated, flooded, frozen or snow-covered ground;
6. the conditions for land application of fertilizer near water courses;
7. procedures for the land application, including rate and uniformity of spreading, of both chemical
fertilizer and livestock manure, that will maintain nutrient losses to water at an acceptable level;
8. limitation of the land application of fertilizers, consistent with good agricultural practice and taking
into account the characteristics of the vulnerable zone concerned, in particular: (a) soil conditions, soil
type and slope; (b) climatic conditions, rainfall and irrigation; (c) land use and agricultural practices,
including crop rotation systems; and to be based on a balance between: (i) the foreseeable nitrogen
requirements of the crops, and (ii) the nitrogen supply to the crops from the soil and from fertilization
corresponding to:
• the amount of nitrogen present in the soil at the moment when the crop starts to use it,
• the supply of nitrogen through the net mineralization of the reserves of organic nitrogen in the soil,
• additions of nitrogen compounds from livestock manure,
• additions of nitrogen compounds from chemical and other fertilizers.
Additional measures that can be taken are:
9 land use management, including the use of crop rotation systems and the proportion of the land area
devoted to permanent crops relative to annual tillage crops;
10. the maintenance of a minimum quantity of vegetation cover during (rainy) periods that will take up
the nitrogen from the soil that could otherwise cause nitrate pollution of water;
11. the establishment of fertilizer plans on a farm-by-farm basis and the keeping of records on fertilizer
use;
12. the prevention of water pollution from run-off and the downward water movement beyond the reach
of crop roots in irrigation systems
Pedo-climatic zones have specific ranges for crop growth potential, surface runoff risk potential and
leaching risk potentials. Pedo-climatic zones are based on climate, landform and soil type
characteristics. In this study, the pedo-climatic zones have been based on two separated layers of
information. The first layer of information is the environmental stratification: the Environmental Zones
(EnZs). The second layer of information deals with the surface run-off risk potential and nitrate leaching
risk potential, based on a combination of landform, soil and climate factors (ie. pedo-climatic
information). These two layers of information have been combined into two maps, showing the surface
run-off risk potential and nitrate leaching risk potential for each ENZs, respectively.
Table 8. The 13 Environmental Zones (EnZs) as the first layer of information for pedo-climatic zonation in Europe.
Nr Environmental Zone Main locations and characteristics
1 Alpine North (ALN) Scandinavian mountains; these have been named Alpine north, because
they show environmental conditions as the Alps on a higher latitude, but
in lower mountains.
2 Alpine South (ALS) The high mountains of central and southern Europe that show the
environmental conditions of high mountains. Also small Alpine patches
are found in mountain areas in Pyrenees and Carpathians.
3 Atlantic North (ATN) The area under influence of the Atlantic ocean and the North sea, humid
with rather low temperatures in summer and winter, but not extremely
cold.
4 Atlantic Central
(ATC)
The area with moderate climate where the average winter temperature
does not go far below 0°C and the average summer temperatures are
relatively low. This is a main agricultural production zone in EU-27.
5 Boreal (BOR) The environmental zone covering the lowlands of Scandinavia
6 Continental (CON) The part of Europe with an environment of warm summers and rather
cold winters. This is a main agricultural production zone in EU-27.
7 Lusitenean (LUS) The southern Atlantic area from western France to Lisbon. Here,
summers are rather warm and sometimes dry, while winters are mild
and humid. This is a main agricultural production zone in EU-27.
8 Mediterranean North
(MDN)
The Mediterranean north represents the major part of the Mediterranean
climate zone with Cork Oak, fruit plantations and Olive groves
9 Mediterranean
Mountains (MDM)
These mountains are influenced by both the Mediterranean and
mountain climates.
10 Mediterranean South
(MDS)
This zone represents the typical Mediterranean climate that is shared
with northern Africa, short precipitation periods in winter and long hot,
dry summers.
11 Nemoral (NEM The zone covering the southern part of Scandinavia, the Baltic states
and Belarus. This is a main agricultural production zone in EU-27.
12 Pannonian (PAN) This is the most steppic part of Europe, with cold winters and dry hot
summers. Most precipitation is found in spring.
13 Anatolian (ANA) Represents the steppes of Turkey, a Mediterranean steppic environment.
Table 8 briefly describes the 13 distinguished EnZs. Figure 5 shows a map of the Environmental Zones
(EnZs) in Europe. The map of the Environmental Zones (EnZs) has been combined with the map of the
utilized agricultural area and with maps indicating the land, soil and climate factors that determine the
surface runoff risk potential and the leaching risk potential. This combining has resulted in a pedo-
climatic zoning that show the surface runoff risk potential (Figure 6) and the leaching risk potential
(Figure 7) for utilized agricultural land within the Environmental Zones. Three classes have been
distinguished for the surface runoff risk potential and the leaching risk potential: low, medium and high.
Figure 5. The Environmental Stratification of Europe.
Figure 6. Map showing the surface runoff risk potential for agricultural land within the Environmental Zones in the
EU-27. Abbreviations of the Environmental Zones are explained in Figure S1 and Table S1. Note that grey areas
indicate non-agricultural areas.
Figure 7. Map showing the leaching risk potential for agricultural land within the Environmental Zones in the EU-27.
Abbreviations of the Environmental Zones are explained in Figure S1 and Table S1. Note that grey areas indicate non-
agricultural areas.
1.7 Recommendations for measures under the Nitrates Directive
Recommendations for measures have the character of a checklist, an encouraging instrument for making
the measures of Annexes II and III of the Nitrates Directive site-specific and tailor-made. Evidently,
this has to be done by the Member States in Action Programmes. Therefore, the recommendations
presented in this report must be seen as just a first step.
Recommendations for measures of Annexes II and III of the Nitrates Directive have been linked to risks
of surface runoff and leaching, whereby ‘risk’ has been perceived as consisting of (i) a frequency
component (the incidence of occurrence), (ii) a mass component (mean loads), and (iii) a vulnerability
component (some water bodies are more vulnerable to pollution and eutrophication than others). Risks
are high when both the incidence of occurrence and the loads are high, and vulnerability of water bodies
is high. Risks are also high when incidence of occurrence and loads are medium and vulnerability of
receiving water body is high. Evidently, when risks are high, recommendations for measures must be
stringent. Conversely, when the risks of surface runoff and leaching are low, the recommendations may
be less stringent. However, the variability in weather conditions and the deleterious impact of nutrient
leaching and runoff on groundwater pollution and eutrophication of surface waters will always
necessitate ‘precautionary measures’.
Measures can be categorized according to the source-pathway-receptor concept, i.e. there are (i) source-
based measures, (ii) pathway-based measures, and (iii) receptor or effects-based measures. Most of the
measures of Annexes II and III of the Nitrates Directive are source-based and pathway-based measures.
Examples of source-based measures are appropriated storage of animal manures and fertilizers,
balanced fertilization, and prohibition periods for and restrictions on the application of manures and
fertilizers. Examples of pathway-based measures are irrigation measures, drainage, buffer strips, green
covers, terracing. Examples of receptor or effects-based measures are dredging and creation of riparian
zones, etc.
The effectiveness of the measures depends on the site-specific adjustments of these general measures
to the pedo-climatic conditions and farming practices. Hence, the ‘recommendations for measures’
basically are the site-specific or region-specific adjustments of the measures to the pedo-climatic
conditions and farming practices, so as to increase their effectiveness. Recommendations for the
implementation of all 12 measures of the Annexes II and III of the Nitrates Directive have been made
specific and for all pedo-climatic zones in EU-27. The report also includes maps of the pedo-climatic
zones for each Member State of the EU-27.
1.7.1 Example recommendations for measures
For periods when the land application of fertilizers and manures is inappropriate or prohibited.
Application of fertilizers and manures is inappropriate and prohibited when the demand of nutrients by
the crop is low or when the risks for surface runoff and leaching of nutrients are high. Risks of nutrient
leaching are most imminent when 1) the natural precipitation (including water liberated by thawing)
exceeds the evapo-transpiration and the water holding capacity of the soil, 2) soils tend to crack which
may lead to preferential flow, 3) soils contain considerable amounts of water-soluble N and P and 4)
the ratio of mineral N to organically-bound N in applied manures, fertilizers and composts is high. Risks
of overland flow, run-off and erosion are most imminent when 1) precipitation (including water
liberated by thawing) exceeds the water infiltration rate into the soil, 2) the land is sloping, 3) the surface
soil layers contain considerable amounts of water-soluble N and P. Note that the risk of runoff is not
influenced by the ratio of mineral N to organically-bound N in applied manures, fertilizers and
composts.
The part B report provides detailed information about the pedo-climatic factors influencing the
prohibition period for pedo-climatic zones. General recommendations can be derived from the
information presented in Table 9, however, farming practices and water vulnerability must be also
considered.
Governing factors
Pedo-climatic zones
Length of growing season
Rainfall surplus outside growing season
Temperature outside growing season
Soil type and drainage
Slope
Farming practices
Crop type and crop rotation
Cover crops
Type of manure
Type of fertilizer
Vulnerability of water bodies
Ecological and chemical status
Travel time of N and P from nearby sources to the water bodies
Table 9. Ranking of precipitation surpluses per month per environmental zone, (green=evapotranspiration exceeding
rainfall in arable crops and on grassland, yellow=evapotranspiration exceeding rainfall on grassland, red=rainfall
exceeding evapotranspiration on both arable crops and grassland; LT = months with average lowest temperature below
0 oC, LP = months with precipitation surplus exceeding a value of minus 150 mm).
ENZs Month:
Jan Feb March April May June July August Sept Oct Nov Dec
ALN LT LT LT LT (LT) LT LT LT
ATN LT LT
ALS LT LT LT LT LT
BOR LT LT LT (LT) LT LT LT
LUS LP
NEM LT LT LT LT LT
ATC
MDM LT LP
MDN LP LP
CON LT LT (LT) LT
PAN LT LT LT
ANA LP LP
MDS LP LP LP
1.7.2 The capacity and construction of storage vessels for livestock manure.
Rationale and general recommendations: The capacity of storage vessels for livestock manure must
be large enough to store the manures produced during the period when the application of manures is
prohibited, plus the amounts produced during a so-called pre-cautionary period. The latter period
accounts for incidental weather extremes, and/or farm management failures, which necessitate a longer
storage duration. Also, the larger the storage vessel, the more application can be adjusted to the time
crops need nutrients (leading to increased manure efficiency). The construction of the storage vessel
must be robust and leak-tight and should be covered preferably to minimize the loss of gaseous
ammonia and the influx of rainwater. The amount of excreted manure in terms of volume is closely
related to the amount of manure in terms of excreted N and P. As N and P excretion are a function of
production level, live weight, feed conversion (and feed ‘digestibility’) and the N and P contents of
feedstuffs, the excreted volumes depend on these factors too. Excretion can be manipulated by
manipulating the feed composition and drinking water supply, by tuning the daily ration of individual
animals to their actual production level, and by the use of for example artificial enzymes (phythase) and
amino acids. The part B report provides detailed information about the assessment of the storage
capacity, as function of animal species and pedo-climatic zone. General recommendations can be
derived from the information presented in Table 10.
Governing factors
Pedo-climatic zones
Length of the period when the land application of manure is inappropriate/prohibited +
precautionary period.
Farming practices
Number and type of animal species
Manure production per animal species
Manure type: solid, liquids and slurries
Addition of bedding material and litter
Addition of cleaning, spilling and rain waters
Bottom sealing
Presence of storage cover
Manure processing and transport
Evaporative losses and decomposition losses
Vulnerability of water bodies
Ecological and chemical status
Travel time of N and P from nearby sources to the water bodies
Table 10. Minimum manure storage capacity (months of manure production) per environmental zone (ENZ) based on
the probability of a precipitation surplus, periods of drought and frost and unforeseeable weather extremes
Nr ENZs Type of crops grown
100%
Arable
100% Grassland
1 ALN – alpine north >10 >9
2 ALS – alpine south >9 >6
3 ATN – Atlantic north >8 >7
4 ATC – Atlantic central >7 >3
5 BOR – boreal >8 >7
6 CON – continental >7 >4
7 LUS – Lusitanian >8 >4
8 MDN – Mediterranean north >5 >2
9 MDM – Mediterranean mountains >8 >3
10 MDS – Mediterranean South >3 >3
11 NEM – Nemoral >7 >5
12 PAN – Pannonian >6 >3
13 ANA – Anatolian >6 >2
1.7.3 Limitation of the land application of fertilizers.
Rationale and general recommendations
The application rate of fertilizer N has to be based on a balance between the foreseeable N
requirements of the crops, and the N supply to the crops from the soil and other sources,
including the amount of available N in the soil at the moment when the crop starts to use it, the
supply of available N through atmospheric deposition, irrigation water, biological fixation and
the net mineralization of organic N in the soil during the growing season, the supply of
available N through livestock manures, composts, residues, wastes and/or any fertilizer. If too
much manure or fertiliser is applied i.e. more than what is needed by crops, the excess nutrients
will to a very limited extent be taken up as luxury consumption. Most of it will accumulate in
the soil and sooner or later will be lost to the environment. Consequently, water protection
requires limitation of fertiliser applications, on the basis of crop requirements. Depending on
the vulnerability of the receiving water body and its quality status, lower applications could be
needed in view of water protection.
1.8 References
Bull, K., Hoft, R., Sutton, M., 2011. Coordinating European nitrogen policies between directives and international
conventions, in: Sutton, M., Howard, C., Erisman, J., Billen, G., Bleeker, A., Grennfelt, P., vans Grinsven,
H., Grizzetti, B. (Eds.), The European Nitrogen Assessment. Cambridge Univeristy Press, Cambridge, UK.
Butterbach-Bahl, K., Kiese, R., Liu, C., 2011. Measurements of Biosphere–Atmosphere Exchange of CH4 in
Terrestrial Ecosystems. pp. 271–287. doi:10.1016/B978-0-12-386905-0.00018-8
EC, 1991. The Nitrates Directive. 91/676/EEC.
EEA, 1995. Europe’s Environment: the Dobris Assessment. Eur. Environ. Agency, Copenhagen.
Erisman, J.W., Billen, G., Bleeker, A., Grennfelt, A., Grinsven, H., Grizzetti, B., 2011. The European Nitrogen
Assessment. Cambridge Univeristy Press, Cambridge.
EU, 2000. The Water Framework Directive. Directive 2000/60/EC.
Fowler, D., Coyle, M., Skiba, U., Sutton, M.A., Cape, J.N., Reis, S., Sheppard, L.J., Jenkins, A., Grizzetti, B.,
Galloway, J.N., Vitousek, P., Leach, A., Bouwman, A.F., Butterbach-Bahl, K., Dentener, F., Stevenson, D.,
Amann, M., Voss, M., 2013. The global nitrogen cycle in the twenty-first century. Philos. Trans. R. Soc. B
Biol. Sci. 368, 20130164–20130164. doi:10.1098/rstb.2013.0164
Galloway, J., Aber, J., Erisman, J., Seitzinger, S., Howart, R., Cowling, E., Cosby, B., 2003. The Nitrogen
Cascade. Bioscience 53, 341. doi:10.1641/0006-3568(2003)053[0341:TNC]2.0.CO;2
Galloway, J.N., Cowling, E.B., 2002. Reactive Nitrogen and The World: 200 Years of Change. AMBIO A J.
Hum. Environ. 31, 64. doi:10.1639/0044-7447(2002)031[0064:RNATWY]2.0.CO;2
Galloway, J.N., Townsend, A.R., Erisman, J.W., Bekunda, M., Cai, Z., Freney, J.R., Martinelli, L.A., Seitzinger,
S.P., Sutton, M.A., 2008. Transformation of the Nitrogen Cycle: Recent Trends, Questions, and Potential
Solutions. Science (80-. ). 320, 889–892. doi:10.1126/science.1136674
Herridge, D.F., Peoples, M.B., Boddey, R.M., 2008. Global inputs of biological nitrogen fixation in agricultural
systems. Plant Soil 311, 1–18. doi:10.1007/s11104-008-9668-3
Jarvis, S., Hutchings, N., Brentrup, F., Olesen, J., Hoek, K., 2011. Nitrogen flows in farming systems across
Europe, in: Sutton, M., Howard, C., Erisman, J., Billen, G., Bleeker, A., Grennfelt, P., vans Grinsven, H.,
Grizzetti, B. (Eds.), The European Nitrogen Assessment. Cambridge Univeristy Press, Cambridge, UK, pp.
211–228. doi:10.1017/CBO9780511976988
Kahn, P., 2001. The human relationship with nature: development and culture. MIT Press, Cambridge.
Leip, A., Achermann, B., Billen, G., Bleeker, A., Bouwman, A.F., Vries, W. De, Dragosits, U., Döring, U.,
Fernall, D., Geupel, M., Herolstab, J., Johnes, P., Christine, A., Gall, L., Monni, S., Nevečeřal, R., Prud,
M., Reuter, H.I., Simpson, D., Seufert, G., Sutton, M.A., Aardenne, J. Van, Voß, M., Winiwarter, W., 2011.
Integrating nitrogen fluxes at the European scale, in: Sutton, M., Howard, C., Erisman, J., Billen, G.,
Bleeker, A., Grennfelt, P., van Grinsven, H., Grizzetti, B. (Eds.), The European Nitrogen Assessment.
Cambridge Univeristy Press, Cambridge, UK, pp. 345–376.
Mueller, N.D., Gerber, J.S., Johnston, M., Ray, D.K., Ramankutty, N., Foley, J.A., 2013. Corrigendum: Closing
yield gaps through nutrient and water management. Nature 494, 390–390. doi:10.1038/nature11907
Odum, E., 1996. Ecology: A bridge between Science and Society. Sinauer Associates, Sunderland, MA.
OECD, 2008. Environmental Performance of Agriculure in OECD Countries since 1990.
OECD, 1991. Environmental Indicators, a Preliminary Set. OECD, Paris (1991).
Oenema, O., Bleeker, A., Braathen, N.A., Budnakova, M., Bull, K., Cermak, P., Geupel, M., Hicks, K., Hoft, R.
Kozlova, N., Leip, A., Spranger, T., Valli, L., Velthof, G., Winiwarter, W., 2011. Nitrogen in current
European policies, in: Sutton, M., Howard, C., Erisman, J., Billen, G., Bleeker, A., Grennfelt, P., vans
Grinsven, H., Grizzetti, B. (Eds.), The European Nitrogen Assessment. Cambridge Univeristy Press,
Cambridge, UK.
Oenema, O., Kros, H., De Vries, W., 2003. Approaches and uncertainties in nutrient budgets: Implications for
nutrient management and environmental policies. Eur. J. Agron. 20, 3–16. doi:10.1016/S1161-
0301(03)00067-4
Oenema, O., Pietrzak, S., 2002. Nutrient management in food production: achieving agronomic and environmental
targets. Ambio 31, 159–168. doi:10.1579/0044-7447-31.2.159
Schlesinger, W., Bernhardt, E., 2013. Biogeochemistry. Elsevier, New York. doi:10.1016/B978-0-12-385874-
0.09991-X
Schröder, J., Scholefield, D., Cabral, F., Hofman, G., 2004. The effects of nutrient losses from agriculture on
ground and surface water quality: The position of science in developing indicators for regulation. Environ.
Sci. Policy 7, 15–23. doi:10.1016/j.envsci.2003.10.006
Smil, V., 2001. Enriching the earth: Fritz Haber, Carl Bosch, and the transformation of world food production.
The MIT Press, Cambridge, MS, London , UKNo Title.
Smil, V., 2000. Phosphorus in the environment: Natural Flows and Human Interfences. Annu. Rev. Energy
Environ. 25, 53–88.
Sutton, M.A., Bleeker, A., Howard, C.M., Bekunda, M., Grizzetti, M., Vries, W. de, van Grinsven, H.J.M., Abrol,
Y.P., Adhya, T.K., Billen, G., Davidson, E.A., Datta, A., Diaz, R., Erisman, J.W., Liu, X.J., Oenema, O.,
Palm, C., Raghuram, N., Reis, S., Scholz, R.W., Sims, T., Westhoek, H., Zhang, F.S., 2013. Our Nutrient
World: The challenge to produce more food and energy with less pollution. Global Overview of Nutrient
Management. Centre of Ecology and Hydrology, Edinburgh on behalf of the Global Partnership on Nutrient
Management and the International Nitrogen Initiative.
Sutton, M.A., Howard, C.M., Erisman, J.W., Billen, G., Bleeker, A., Grennfelt, P., van Grinsven, H., Grizzetti,
B., 2011. The European Nitrogen Assessment: Sources, Effects and Policy Perspectives. Cambridge
Univeristy Press, Cambridge.
ten Brink, P., Badura, T., Bassi, S., Gantioler, S., Kettunen, M., Rayment, M., Pieterse, M., Daly, E., Gerdes, H.,
Lago, M., Lang, S., Markandya, A., Nunes, P., Ding, H., Tinch, R., Dickie, I., 1991. Estimating the Overall
Economic Value of the Benefits provided by the Natura 2000 Network. Comm. Contract
07.0307/2010/581178/SER/B3.
TFIAM/CIAM, 2006. Review of the Gothenburg Protocol. CIAM Rep. 1/2007.
Tuinstra, W., Hordijk, L., Kroeze, C., 2006. Moving boundaries in transboundary air pollution co-production of
science and policy under the convention on long range transboundary air pollution. Glob. Environ. Chang.
16, 349–363. doi:10.1016/j.gloenvcha.2006.03.002
UNECE, 1991. the Gothenburg Protocol. United Nations Econ. Comm. Eur.
Van Beek, C., Brouwer, L., Oenema, O., 2003. The use of farmgate balances and soil surface balances as estimator
for nitrogen leaching to surface water. Nutr. Cycl. Agroecosystems 67, 233–244.
doi:10.1023/B:FRES.0000003619.50198.55
Watson, C., Atkinson, D., 1999. Using nitrogen budgets to indicate nitrogen use efficiency and losses from whole
farm systems: A comparison of three methodological approaches. Nutr. Cycl. Agroecosystems 53, 259–
267. doi:10.1023/A:1009793120577
2 Principles of overall nitrogen management: working
group report
Author: Oene Oenema
The following chapter builds upon the “the principles of overall nitrogen management: background
document (chapter 1)” and provides a summary of discussions held during the workshop by the
working group for this theme.
1. Group composition
The working group for theme 1 comprised approximately 20 people with interests in nitrogen
management at the science-policy-practice interfaces, and with the purpose to increase nitrogen (N) use
efficiency and decrease N losses to air, groundwater and surface waters. Countries represented were
Belgium, Canada, Czech Republic, Denmark, the EU Commission, France, Germany, Italy, the
Netherlands, Norway, Poland, Portugal, Spain, Ukraine and the United Kingdom.
2. Boundaries
It was agreed that the focus of the report should remain as N but, there should be strong linkages to
other essential nutrient elements in crop and animal production, as well as to carbon (sequestration) and
water use. Managing N without considering other essential growth factors is useless.
Nitrogen management must consider the environmental conditions, including climate/weather,
geomorphology, soil quality and hydrology, as well as the socio-economic conditions. Nitrogen
management must also consider the various (different) cropping system as well as the various different
animal production systems. Hence, N management is by definition ‘site-specific’.
The participants agreed to focus on the whole food production- processing- consumption system. The
link with industry and especially combustion (NOx) was not discussed/considered.
3. Knowledge and data gaps
The usefulness of a joined-up overall N Guidance Document will depend on the completeness and
robustness of the underlying data, models and assumptions. It is important therefore to identify
successful cases, knowledge gaps and uncertainties, the extent to which these may compromise
guidance and what steps might be taken to address this. So far there is little coherent information about
overall nitrogen management, and hence that the main purpose of the working group would be to collect
and synthesize the available information and concepts. The group agree that the emphasis should be on
synthesis of current information and ideas (and not on identifying knowledge and gaps).
4. Existing guidance
There is as yet no comprehensive guidance document for overall N management. Instead, a range of
existing guidance documents/sources regarding N use, losses and mitigation in the context of managed
agricultural land are available, and have been listed in part in the background document. Important
documents include:
Options for Ammonia Abatement: Guidance from the UNECE Task Force on Reactive
Nitrogen (http://www.clrtap-tfrn.org/content/options-ammonia-abatement-guidance-unece-
task-force-reactive-nitrogen)
EU-Nitrate Directive good agricultural practice guidance regulations.
EU-Water Framework water basin management plans.
HELCOM Baltic Sea Action Plan (http://helcom.fi/baltic-sea-action-plan) See p86-96 for
agricultural measures
EU Project report: ‘Resource efficiency in Practice – Closing Mineral Cycles’
(http://ec.europa.eu/environment/water/water-
nitrates/pdf/Closing_mineral_cycles_final%20report.pdf) See p87 onwards. Also see project
outputs - Region-specific leaflets on best-practices
(http://ec.europa.eu/environment/water/water-nitrates/index_en.html)
Mainstreaming climate change into rural development policy post 2013. European
Commission 2014
(http://ecologic.eu/sites/files/publication/2015/mainstreaming_climatechange_rdps_post2013
_final.pdf) See Table 3 for list of measures
National codes for good agricultural practice and national fertilizer recommendations
Industry-related fertilization recommendation and animal feeding guidance.
NGO-related suggestions for best management practices.
3 Housed livestock, manure storage, and
manure processing: background document
Author: Barbara Amon and Isabelle Weindl
The following chapter provides an overview on nitrogen management for housed livestock, manure
storage and manure processing in agriculture, and was used as a background document by the “Housed
livestock, manure storage, and manure processing working group”.
3.1 Why do we have emissions and how can they be influenced – the basics behind
emission processes
Nitrogen can take various forms (Figure 8). Reactive nitrogen (Nr) includes all forms of nitrogen that
are biologically, photochemically, and radiatively active. Compounds of nitrogen that are reactive
include the following: nitrous oxide (N2O), nitrate (NO3 -), nitrite (NO2 -), ammonia (NH3), and
ammonium (NH4 +). Reactive forms of nitrogen are those capable of cascading through the environment
and causing an impact through smog, acid rain, biodiversity loss, etc2. The design of mitigation
measures requires a sound knowledge of the processes that influence formation and emission of
ammonia (NH3), nitrous oxide (N2O) and dinitrogen (N2).
2 http://www.n-print.org/node/5
Figure 8. Forms of reactive nitrogen
3.1.1 Ammonia
The principles of ammonia formation and its influencing factors are well known. Degradation of
nitrogen containing organic substance results in ammonium formation (NH4+). There is an equilibrium
between ammonium and ammonia:
H2O + NH3 ⇌ OH− + NH4+
The degree to which ammonia forms the ammonium ion depends on the pH of the solution. If the pH is
low, the equilibrium shifts to the right: more ammonia molecules are converted into ammonium ions.
If the pH is high, the equilibrium shifts to the left: the hydroxide ion abstracts a proton from the
ammonium ion, generating ammonia.
Ammonia emissions are governed by the difference between solution and atmosphere NH3 partial
pressure. High NH3 concentrations in the solution and low NH3 concentrations in the surrounding
atmosphere increase NH3 emissions. According to Henry´s Law, ammonia emissions are also by
temperature dependent with rising temperatures increasing emissions (Figure 9).
Denmead et al. (1982) give the following equation:
NH3(solution) = NH3(solution) + NH4 (solution) /1 + 100.09018+(2729.92/T)- pH
NH3(solution) = NH3 concentration in the solution
NH3(solution) + NH4 (solution) = NH3 and NH4+ in the solution
T = Temperature in the solution [K]
pH = pH value in the solution
Figure 9. NH3 concentration in the solution depending on temperature for pH 7.0 and pH 7.5 (Denmead at al. 1982)
3.1.2 N2O and N2
The principles of micro biologic formation of N2O and N2 are well known and have been described by
a range of authors. N2O, NOx and N2 are formed during nitrification and denitrification. The “Leakage
model” developed by Firestone & Davidson (1989) shows N2O, and NOx losses as leakage flows during
nitrification and denitrification (Figure 10).
Figure 10. Leakage model for N2O and NOx losses during nitrification and denitrification (Firestone & Davidson 1989)
Nitrification oxidises ammonia via nitrite to nitrate. This process is strictly aerobic. Autotrophic
nitrifying bacteria belong to the widespread groupd of nitrosomonas, nitrospira and nitrobacter. They
growth is reliant on sources of CO2, O2 and NH4. Availability of NH4 is mostly the limiting factor as
CO2 and O2 are available in abundance. Low pH, lack of P and temperatures below 5°C or above 40 °C
lead to a reduction in nitrification activities. A water content of 60% is optimal for the nitrification
process.
With low pH values, nitrification is carried out by bacteria and funghi. In contrast to the autotrophic
nitrifiers, they need carob sources for their growth. Their turnover rate is much lower compared to the
autotrophic nitrifiers, but still a substantial total turnover can be achieved as a wider range of species
has the ability for heterotrophic nitrification. N2O production during nitrification is around 1%, NO
production ranges between 1 and 4 %.
Denitrification reduces nitrate to N2O, NO or N2 when oxygen availability is low. NO3-, NO and N2O
serve as alternative electron acceptors when O2 is lacking. Molecular N2 is the last part of the reaction
chain. Denitrification is the only biological process that can turn reactive nitrogen into molecular N2.
Denitrifying bacteria are heterotrophic and facultative anaerobic. This means that they use O2 as
electron acceptor and switch to alternative electron acceptors (NO3-, NO and N2O) when oxygen
availability is low. Denitrifying bacteria are wide spread and show a high biodiversity.
Influences on denitrification have been extensively investigated mainly under lab conditions. Complex
interactions exist between the various influencing factors which make a prediction of N2O emissions
difficult under practical conditions.
Denitrification is mainly governed by oxygen availability. Denitrification starts when the O2 content
falls below 5%. This may be in the case in poorly aerated soils, but also in soils where a high turnover
rate exceeds oxygen supply. Easily degradable carbon and nitrate concentrations also influence the
denitrification rate. Low temperature and low pH value limit denitrification.
The relationship between N2 and N2O formation is mainly governed by the relationship between
electron acceptor and reducing agent and by the O2 content in the substrate. N2 is only formed under
anaerobic conditions and a wide C: NO3- ratio. High nitrate concentrations increase the rate of N2O
production.
3.2 Livestock feeding
Ammonia emissions result from the degradation of urea by the ubiquitary enzyme urease which results
in NH4+ formation. Urea is mainly excreted in the urine and is much more prone to ammonia losses
than organic nitrogen excreted in the faeces. Crude protein (CP) content and composition in the animal
diet is the main driver of urine excretion. Excess CP is excreted and can be lost in the manure
management chain. Adaptation of crude protein in the diet to the animals´ needs is therefore the first
and most efficient measure to mitigate nitrogen emissions.
Reduction of crude protein in animal feed is one of the most cost-effective and strategic ways of
reducing NH3 emissions. For each per cent (absolute value) decrease in protein content of the animal
feed, NH3 emissions from animal housing, manure storage and the application of animal manure to land
are decreased by 5%–15%, depending also on the pH of the urine and dung. Low-protein animal feeding
also decreases N2O emissions, and increases the efficiency of N use in animal production. Moreover,
there are no animal health and animal welfare implications as long as the requirements for all amino
acids are met.
Low-protein animal feeding is most applicable to housed animals and less for grassland-based systems
with grazing animals, because grass is in an early physiological growth stage and thus high in
degradable protein, and grassland with leguminous species (e.g., clover and lucerne) have a relatively
high protein content. While there are strategies to lower the protein content in herbage (balanced N
fertilization, grazing/harvesting the grassland at later physiological growth stage, etc.), as well as in the
ration of grassland-based systems (supplemental feeding with low-protein feeds), these strategies are
not always fully applicable.
3.2.1 Feeding strategies for dairy and beef cattle
Lowering CP of ruminant diets is an effective strategy for decreasing NH3 loss. The following
guidelines hold:
(a) The average CP content of diets for dairy cattle should not exceed 15%–16% in the dry
matter (DM) (Broderick, 2003; Swensson, 2003). For beef cattle older than 6 months this could
be further reduced to 12%;
(b) Phase feeding can be applied in such a way that the CP content of dairy diets is gradually
decreased from 16% of DM just before parturition and in early lactation to below 14% in late
lactation and the main part of the dry period;
(c) Phase feeding can also be applied in beef cattle in such a way that the CP content of the diets
is gradually decreased from 16% to 12% over time.
In many parts of the world, cattle production is grassland-based or partly grassland-based. In such
systems, protein-rich grass and grass products form a significant proportion of the diet, and the target
values for CP may be difficult to achieve, given the high CP content of grass from managed grasslands.
The CP content of fresh grass in the grazing stage (2,000–2,500 kg DM/ha) is often in the range of
18%–20% (or even higher, especially when legumes are present), the CP content of grass silage is often
between 16% and 18% and the CP content of hay is between 12% and 15% (e.g., Whitehead, 2000). In
contrast, the CP content of maize silage is only in the range of 7%–8%. Hence, grass-based diets often
contain a surplus of protein and the magnitude of the resulting high N excretion strongly depends on
the proportions of grass, grass silage and hay in the ration and the protein content of these feeds. The
protein surplus and the resulting N excretion and NH3 losses will be highest for grass (or grass-legume)-
only summer rations with grazing of young, intensively fertilized grass or grass legume mixtures.
However, urine excreted by grazing animals typically infiltrates into the soil before substantial NH3
emissions can occur and overall NH3 emissions per animal are therefore less for grazing animals than
for those housed where the excreta is collected, stored and applied to land.
The NH3 emission reduction achieved by increasing the proportion of the year the cattle spent grazing
outdoors will depend on the baseline (emission of ungrazed animals), the time the animals are grazed,
and the N fertilizer level of the pasture. The potential to increase grazing is often limited by soil type,
topography, farm size and structure (distances), climatic conditions, etc. It should be noted that grazing
of animals may increase other forms of N emissions (e.g., nitrate-N leaching and N2O emissions).
However, given the clear and well quantified effect on NH3 emissions, increasing the period that
animals are grazing all day can be considered as a strategy to reduce emissions, but depending on
grazing time. The actual abatement potential will depend on the base situation of each animal sector in
each country. Changing from a fully housed period to grazing for part of the day is less effective in
reducing NH3 emissions than switching to complete (24-hour) grazing, since buildings and stores
remain dirty and continue to emit NH3.
In general, increasing the energy/protein ratio in the diet by using “older” grass (higher sward surface
height) or swathed forage cereal and/or supplementing grass by high energy feeds (e.g., silage maize)
is a well proven strategy. However, for grassland-based ruminant production systems, the feasibility of
these strategies may be limited, as older grass may reduce feeding quality, especially when conditions
for growing high energy feeds are poor (e.g., warm climates), and therefore have to be purchased.
Hence, full use of the grass production would no longer be guaranteed.
3.2.2 Feeding strategies for pigs
Feeding measures in pig production include phase feeding, formulating diets based on
digestible/available nutrients, using low-protein amino acid-supplemented diets, and feed
additives/supplements. Further techniques are currently being investigated (e.g., different feeds for
males (boars and castrated males) and females) and might be additionally available in the future.
The CP content of the pig ration can be reduced if the amino acid supply is optimized through the
addition of synthetic amino acids (e.g., lysine, methionine, threonine, tryptophan) or special feed
components, using the best available information on “ideal protein” combined with dietary
supplementation.
A CP reduction of 2%–3% in the feed can be achieved, depending on pig production category and the
current starting point. It has been shown that a decrease of 1% CP in the diet of finishing pigs results in
a 10% lower total ammoniacal nitrogen (TAN) content of the pig slurry and 10% lower NH3 emissions
(Canh and others, 1998).
3.2.3 Feeding strategies for poultry
For poultry, the potential for reducing N excretion through feeding measures is more limited than for
pigs because the conversion efficiency currently achieved on average is already high and the variability
within a flock of birds is greater. A CP reduction of 1%–2% may be achieved depending on the species
and the current starting point. Further applied nutrition research is currently being carried out in EU
member States and North America and this may support further possible reductions in the future. A
reduction of the CP content by 1%–2% is a well proven measure for growers and finishers.
3.3 Livestock Housing
Chadwick et al. (2011) state in their paper on “Manure management: Implications for greenhouse gas
emissions”: Manure management is a continuum from generation by livestock to storage and treatment
and finally to land spreading. There is the potential for NH3, N2O and CH4 emissions at each stage of
this continuum. For describing and estimating NH3 emissions from the manure management continuum,
a mass flow approach has been used (Webb and Misselbrook, 2004) as this allows effects of
management at one phase that reduces emissions and conserves manure N to be considered as the
manure passes to the next stage in the continuum. Other gaseous N losses, including N2O, are included
in this mass flow in a manner similar to that of Dämmgen and Hutchings (2008). The importance of
this whole system approach is that effects of mitigation methods at one stage are considered in
downstream stages (Sommer et al., 2009).
3.3.1 Cattle housing
When using measures to abate emission from cattle houses, it is important to minimize loss of the
conserved NH3 during downstream handling of the manure, in storage and spreading to maximize the
benefit from the cost of abatement.
Housing systems for cattle vary across the United Nations Economic Commission for Europe (UNECE)
region. While loose housing is most common, dairy cattle are still kept in tied stalls in some countries.
In loose housing systems all or part of the excreta is collected in the form of slurry. In systems where
solid manure is produced (such as straw-based systems), it may be removed from the house daily or it
remain there for up to the whole season, such as in deep litter stables. The system most commonly
researched is the “cubicle house” for dairy cows, where NH3 emissions arise from fouled slatted and/or
solid floors and from manure in pits and channels beneath the slats/floor.
Animal welfare considerations tend to lead to an increase of soiled walking area per animal, increased
ventilation, possibly cooler winter temperatures and an overall increase in emissions. Changes in
building design to meet the new animal welfare regulations in some countries (e.g., changing from tied
stall to cubicle housing) will therefore increase NH3 emissions unless abatement measures are
introduced at the same time to combat this increase.
Solid versus slurry manure systems. Straw-based systems producing solid manure for cattle are not
likely to emit less NH3 in the animal houses than slurry-based systems. Further, N2O and di-nitrogen
(N2) losses due to (de)nitrification tend to be larger in litter-based systems than slurry-based systems.
While straw-based solid manure can emit less NH3 than slurry after surface spreading on fields (e.g.,
Powell and others, 2008), slurry provides a greater opportunity for reduced emissions applications. The
physical separation of faeces (which contains urease) and urine in the housing system reduces
hydrolysis of urea, resulting in reduced emissions from both housing and manure spreading (Burton,
2007; Fangueiro and others, 2008a, 2008b; Møller and others, 2007). Verification of any NH3 emission
reductions from using solid-manure versus slurry-based systems and from solid-liquid separation
should consider all the stages of emission (housing, storage and land application).
Mitigation options: Mitigation options can be grouped into the following types:
Floor based systems and related management techniques (including scrapers and cleaning
robots);
Litter based systems (use of alternative organic material);
Slurry management techniques at pit level;
Indoor climate control techniques;
End-of-pipe techniques (hybrid ventilation + air cleaning techniques) and GHGs mitigation
techniques.
Several pathways can be identified to further optimize existing and develop new mitigation techniques.
With this respect emission reduction techniques at animal housing level should aim to affect one or
more of the following important key factors and/or driving forces of the ammonia emission process:
Draining capacity of the floor for direct transportation of urine to the manure storage
Residence time of open urine/manure sources;
Emitting surface area of open urine/manure sources;
Urease activity in urine puddles;
Urine/manure pH and temperature;
Indoor air temperature;
Air velocities at emitting surfaces (urine puddles and manure surface in the pit);
Air exchange between pit headspace and indoor air;
Exhaust of indoor air.
The “grooved floor” system for dairy and beef cattle housing, employing “toothed” scrapers running
over a grooved floor, is a reliable technique to abate NH3 emissions. Grooves should be equipped with
perforations to allow drainage of urine. This results in a clean, low-emission floor surface with good
traction for cattle to prevent slipping. Ammonia emission reduction ranges from 25% to 46% relative
to the reference system (Smits, 1998; Swierstra, Bram and Smits, 2001).
In houses with traditional slats (either non-sloping, 1% sloping or grooved), optimal barn climatization
with roof insulation (RI) and/or automatically controlled natural ventilation (ACNV) can achieve a
moderate emission reduction (20%) due to the decreased temperature (especially in summer) and
reduced air velocities (Braam, Ketelaars and Smits 1997; Bram and others, 1997; Smits, 1998; Monteny,
2000).
Decreasing the amount of animal excrement in animal housing systems through increased grazing is an
effective measure to decrease NH3 emissions. Though emissions from grazing will increase when
animals are kept outside, NH3 emissions from animal housing systems will decrease much more,
provided surfaces in the house are clean while the animals are grazing outside. Total annual emissions
(from housing, storage and spreading) from dairy systems may decrease by up to 50% with nearly all-
day grazing (Bracher and others, forthcoming), as compared with animals that are fully confined. While
increased grazing is a reliable emission reduction measure for dairy cows, the amount of emission
reduction depends on the daily grazing time and the cleanliness of the house and holding area. Grazing
is efficient in reducing NH3 emissions, if the animals are grazed all day or if very little floor area is
contaminated with manure each day. Less than 18 grazing hours per day must be considered as category
2 because of the uncertainty in quantifying emissions. In some cases grazing can contribute to increased
leaching or increased pathogen and nutrient loading of surface water.
Different improved floor types based on slats or solid, profiled concrete elements have been tested.
These designs combine emission reduction from the floor (increased run-off of urine) and from the pit
(reduction of air exchange by rubber flaps in the floor slots). The emission abatement efficiency depends
on the specific technical characteristics of the system.
Bedding material in animal housing can affect NH3 emission. The physical characteristics (urine
absorbance capacity, bulk density) of bedding materials are of more importance than their chemical
characteristics (pH, cation exchange capacity, carbon to nitrogen ratio) in determining NH3 emissions
from dairy barn floors (Misselbrook and Powell, 2005; Powell, Misselbrook and Casler, 2008; Gilhespy
and others, 2009). However, further assessment is needed on the effect of bedding on emissions for
specific systems while taking into account the whole manure management path.
Chemical or acid air scrubbers, while effective in decreasing NH3 emissions from force-ventilated pig
housing, cannot generally be implemented in cattle housing which are mostly naturally ventilated across
the ECE region. Also, there are few data for scrubbers on cattle (Ellen and others, 2008).
3.3.2 Pig housing
Designs to reduce NH3 emissions from pig housing systems have been described in detail in European
Commission (2003) and in the IPPC “BAT” document, and apply the following principles:
Reducing manure surfaces such as soiled floors, slurry surfaces in channels with sloped walls. Partly
slatted floors (~50% area), generally emit less NH3, particularly if the slats are metal- or plastic-coated
rather than concrete, allowing the manure to fall rapidly and completely into the pit below. Emissions
from the non-slatted areas are reduced by inclined, smooth surfaces, by locating the feeding and
watering facilities to minimize fouling these areas, and by good climate control in the building;
Removing the slurry from the pit frequently to an external slurry store with vacuum or gravity
removal systems or by flushing systems at least twice a week;
Additional treatment, such as liquid/solid separation;
Circulating groundwater in floating heat exchangers to cool the surface of the manure in the
under-floor pit to at least 12°C. Constraints include costs and need to locate a source of
groundwater away from the source of drinking water;
Changing the chemical/physical properties of the manure such as decreasing pH;
Using surfaces which are smooth and easy to clean (see subpara. (a) above);
Treatment of exhaust air by acid scrubbers or biotrickling filters;
Lowering the indoor temperature and ventilation rate, taking into account animal welfare and
production considerations, especially in winter;
Reducing air flow over the manure surface.
For a given slat width, manure drains from concrete slats less efficiently than from steel- and plastic-
covered slats and this is associated with greater emissions of NH3. Note that steel slats are not allowed
in some countries for animal welfare reasons. These cross-media effects have been taken into account
in defining BAT for the various housing designs. For example, frequent flushing of slurry (normally
once in the morning and once in the evening) causes nuisance odour events. Flushing slurry also
consumes energy unless manually operated passive systems are used.
Use of straw in pig housing is expected to increase due to concern for the welfare of the pigs. In
conjunction with (automatically controlled) naturally ventilated housing systems, straw allows the
animals to self-regulate their temperature with less ventilation and heating, reducing energy
consumption. In systems with litter, the pen is sometimes divided into solid areas with litter and slatted
dunging areas. However, pigs do not always use these areas in the desired way, using the littered area
to dung and the slatted area to cool off in warm weather. Generally, pens should be designed to
accommodate desired excreting behaviour of pigs to minimize fouling of solid floors. This is more
difficult in regions with a warm climate. Note that integrated evaluation of straw use should consider
the added cost of the straw and mucking out the pens; possible increased emissions from storage and
application of manure with straw; and the benefit of adding organic matter to the soil.
The reference system, used commonly in Europe, is a fully slatted floor with a deep manure pit
underneath and mechanical ventilation; emission ranges from 2.4 to 3.2 kg NH3 per pig place per year.
Since growers/finishers are always housed in a group, most systems used for group housing of sows are
applicable to growers.
Ammonia emission can be reduced by 25% by reduction of emitting surface area through frequent and
complete vacuum-assisted drainage of slurry from the floor of the pit. Where this is possible to do, this
technique has no cost. Partly slatted floors covering 50% of floor area generally emit 15%–20% less
NH3, particularly if the slats are metal or plastic-coated which is less sticky for manure than concrete.
Decreasing risk of emissions from the solid part of the floor can be achieved by using an inclined (or
convex), smoothly finished surface; by appropriate siting of the feeding and watering facilities to
minimize fouling of the solid areas; and by good climate control (Aarnink and others, 1996; Guigand
and Courboulay, 2007; Ye and others, 2008a, 2008b). Further reduction of the emitting area can be
achieved by making both the partly slatted area and the pit underneath smaller. With the smaller slatted
area, the risk of greater fouling of the solid area can be mitigated by installing a small second slatted
area with a water canal underneath at the other side of the pen where the pigs tend to eat and drink. The
canal is filled with about two centimetres (cm) of water to dilute any manure that might eventually drop
into it. This slatted area will have low emissions because any manure dropped here will be diluted. This
combined manure-canal and water-canal system can reduce NH3 emissions by 40%–50% depending on
the size of the water canal.
Reducing the emitting surface area by having one or two slanted pit walls, in combination with partly
slatted floors and frequent manure removal, can reduce emissions by up to 65%. Reducing the emitting
surface area with shallow V-shaped gutters (maximum 60 cm wide, 20 cm deep) can reduce emission
in pig houses by 40% to 65%, depending on pig category and the presence of partly slatted floors. The
gutters should be flushed twice a day with the liquid (thin) fraction of the slurry rather than water;
flushing with water dilutes the manure and increases the cost of transporting it.
Reducing NH3 emissions can also be achieved by acidifying the slurry to shift the chemical balance
from NH3 to NH4+. The manure (especially the liquid fraction) is collected into a tank with acidified
liquid (usually sulphuric acid, but organic acids can be used as well) maintaining a pH of less than 6.
In piglet housing emission reduction of 60% has been observed. Surface cooling of manure with fins
using a closed heat exchange system is a technique with a reduction efficiency of 45%–75% depending
on animal category and surface of cooling fins. This technique is most economical if the collected heat
can be exchanged to warm other facilities such as weaner houses (Huynh and others, 2004). In slurry
systems this technique can be retrofitted into existing buildings. This system is not applicable when
straw bedding is used or when the feed contains a lot of roughage because a layer of floating residue
may develop on top of the slurry.
Treatment of exhaust air by acid scrubbers (mainly sulphuric acid) or biotrickling filters has proven to
be practical and effective for large-scale operations in Denmark, Germany, France and the Netherlands
(e.g., Melse and Ogink, 2005; Guingand, 2009). This is most economical when installed in new houses
because retrofitting in existing housing requires costly modification of ventilation systems. Acid
scrubbers have demonstrated NH3 removal efficiencies of 70%–90%, depending on their pH-set values.
Scrubbers and biotrickling filters also reduce odour and particulate matter by 75% and 70%,
respectively (Guingand, 2009). Further information is needed on the suitability of these systems in
South and Central Europe. Operational costs of both acid scrubbers and trickling filters are especially
dependent on the extra energy use for water recirculation and to overcome increased back pressure on
the fans. Optimization methods are available to minimize costs (Melse, Hofschereuder and Ogink,
2012) and costs will be lower for large operations.
3.3.3 Poultry housing
Designs to reduce NH3 emissions from poultry housing systems apply the following principles:
Reducing emitting manure surfaces;
Removing the manure frequently to an external slurry store (e.g., with belt removal systems);
Quickly drying the manure;
Using surfaces which are smooth and easy to clean;
Treatment of exhaust air by acid scrubbers or biotrickling filters;
Lowering the indoor temperature and ventilation as animal welfare and/or production allow.
3.3.4 Housing systems for laying hens
The evaluation of housing systems for layers in the EU member States has to consider the requirements
laid down by Council Directive 1999/74/EC of 19 July 1999 laying down minimum standards for the
protection of laying hens. This Directive prohibits the use of conventional cage systems starting in 2012.
Instead, only enriched cages (also called furniture cages), or non-cage systems, such as litter (or deep
litter) housing systems or aviary systems, are allowed.
Ammonia emissions from battery deep-pit or channel systems can be lowered by reducing the moisture
content of the manure by ventilating the manure pit. The collection of manure on belts and the
subsequent removal of manure to covered storage outside the building can also reduce NH3 emissions,
particularly if the manure has been dried on the belts through forced ventilation. The manure should be
dried to 60%–70% DM to minimize the formation of NH3. Manure collected from the belts into
intensively ventilated drying tunnels, inside or outside the building, can reach 60%–80% DM content
in less than 48 hours, but in this case exposure to air and emissions are increased. Weekly removal from
the manure belts to covered storages reduces emissions by 50% compared with bi-weekly removal. In
general, emission from laying hen houses with manure belts will depend on: (a) the length of time that
the manure is present on the belts; (b) the drying systems; (c) the poultry breed; (d) the ventilation rate
at the belt (low rate = high emissions); and (e) the feed composition. Aviary systems with manure belts
for frequent collection and removal of manure to closed storages reduce emission by more than 70%
compared with the deep litter housing system.
Treatment of exhaust air by acid scrubber or biotrickling filters has been successfully employed in
several countries (Melse and Ogink, 2005; Ritz and others, 2006; Patterson and Adrizal, 2005; Melse,
Hofschreuder and Ogink, 2012). Acid scrubbers remove 70%–90% of NH3, while biological scrubbers
remove 70%; both also remove fine dust and odour. To deal with the high dust loads, multistage air
scrubbers with prefiltering of coarse particles have been developed (Ogink and Bosma, 2007; Melse,
Ogink and Bosma, 2008). Yet some Parties consider this technique as only category 2 because of the
dust loading issue.
3.3.5 Housing systems for broilers
To minimize NH3 emission in broiler housing, it is important to keep the litter dry. Litter moisture and
emissions are influenced by:
Drinking-water design and function (leakage and spills);
Animal weight and density, and duration of the growing period;
Ventilation rate, use of in-house air purification and ambient weather;
Use of floor insulation;
Type and amount of litter;
Feed.
Reducing spillage of water from the drinking system: A simple way to reduce spillage of water from
the drinking system is using a nipple instead of bell drinkers.
Air scrubber technology to remove NH3 from ventilation air is highly effective, but not widely
implemented because of costs. Packed-bed filters and acid scrubbers currently available in the
Netherlands and Germany remove 70%–90% of NH3 from exhaust air. Questions about long-term
reliability due to high dust loads must be further clarified. Various multi-pollutant scrubbers have been
developed to also remove odor and particulate matter (PM10 and PM2.5) from the exhaust air (Zhao
and others, 2011; Ritz and others, 2006; Patterson and Adrizal, 2005).
3.4 Manure Storage and Processing
Sustainable agriculture must aim at an optimal use of manure nutrients. Nutrients may be lost via nitrate
leaching and via gaseous emissions (NH3, N2O, NOx, and N2). Besides nutrient losses, methane
emissions to the atmosphere must be reduced as far as possible.
Slurry composition is not ideal with regard to fertiliser properties and low emission handling. In
particular, the high dry matter and carbon content pose several problems during storage, and during and
after slurry application (Table 11).
Table 11. Problems resulting from slurry high dry matter and carbon content
Problem
storage crust formation and sedimentation of solids
high energy consumption for pumping and mixing
emission of NH3, N2O, CH4, and odor
spreading NH3 losses
high technical effort for even and low emission application
suffering of plants due to etching by slurry
fertilisation less effective than mineral fertilizer
effect less predictable than from mineral fertilizer
N immobilisation in the soil
denitrification and subsequent N2O emissions
Slurry dry matter tends to crust formation on the slurry surface and/or to sedimentation on the bottom
of the slurry tank. In order to achieve an even distribution of nutrients in the slurry, slurry must be
homogenised prior to application. Homogenisation of slurry with high dry matter content is energy
consuming and increases NH3 emissions as slurry comes to close contact with the atmosphere. Thus,
slurry homogenisation is to be reduced as far as possible which is only possible if slurry dry matter
content is reduced.
Slurry contains considerable amounts of easily degradable carbon that serves as nutrient source to
microbes. During slurry storage a continuous degradation of organic matter can be observed.
Degradation intensity is strongly dependent on slurry dry matter content. Amon et al. (1995)
investigated changes in slurry composition over a 200-day storage period. Cattle, beef and pig slurry
was stored in 250-l-tanks. The influence of slurry dry matter content on changes in slurry composition
was tested with three different dry matter contents. Degradation or organic matter was significantly
greater with higher slurry dry matter content.
As conditions in the slurry are anaerobic, degradation of organic matter must always occur with
anaerobic pathways. This means, that CH4 and CO2 are formed as end products of the degradation
process. It is thus to be assumed that high dry matter slurry bears a greater risk for CH4 emissions.
After application NH3 emissions increase with an increase in slurry dry matter content. Ammonia
emissions not only have negative environmental impacts, but are also a loss of a valuable plant nutrient
that has in consequence to be bought as mineral fertiliser.
Figure 11. Changes in slurry composition to be achieved by successful manure treatment
Environmentally friendly slurry application requires the slurry to be evenly applied near or under the
surface. It is much more complicated to fulfil this requirement when the slurry has a high dry matter
content than when it has a low viscosity and can easily flow through band spreading hoses.
N availability to plants is difficult to calculate with high dry matter slurry. The narrower the C/N-ratio,
and the higher NH4-N content the more N is available to plants right after slurry application. With a
wide C/N-ratio, part of slurry N is immobilised in the soil N pool and becomes available only at a later
and non predictable stage. In addition, an increase in soil N content goes along with an increase in
denitrification rate and subsequent N2O losses (Dosch 1996).
It is thus necessary to reduce slurry dry matter and carbon content at an early stage of manure
management. This leads to several manure treatment options that have to be evaluated against the
requirements listed in Figure 11.
There are various techniques of manure treatment that can be classified as physical, chemical or
biological way of treatment (Figure 12). Manure treatment options presented in this chapter will be
evaluated against the following criteria:
reduction in dry matter content
item reduction in carbon content
narrowing of C/N ratio
impact on NH3, N2O and CH4 emissions
energy consumption
impact on effort for slurry application
influence on slurry properties as fertiliser
costs
Figure 12. Options of manure treatment
Slurry mixing is the most commonly applied manure treatment technology. Slurry is homogenised prior
to application in order to achieve an even distribution of nutrients. Apart from this, mixing does not
offer any additional benefits compared to untreated slurry. Neither dry matter nor carbon content are
reduced. C/N-ratio is not altered. No reduction in NH3, N2O or CH4 emissions is to be expected (Table
12).
Table 12. Assessment of impacts achieved by slurry mixing
criteria result achieved by mixing
energy consumption cattle slurry: 0.91 kWh m-3
pig slurry: 3.25 kWh m-3
DM and C content not changed
C/N-ratio not changed
pH not changed
NH3, N2O and CH4 losses not changed, maybe increase
N losses 11—22 % (during mixing)
costs 0.41- 0.64 EURO m-3
effort for slurry application high, not changed
fertilising effects not changed
Slurry dilution with water can reduce NH3 losses after slurry application. However, a significant effect
it only achieved if water-to-slurry-ratio is at least 2:1 (Beudert et al. 1988). This would result in a
dramatic increase in slurry volume that has to be stored and applied. Nutrient composition stays
unchanged and thus slurry fertiliser quality is not improved. Water dilution has positive effects only in
some criteria and cannot be recommended as very effective manure treatment option (Table 13).
Table 13. Assessment of impacts achieved by dilution with water
criteria result achieved dilution with water
energy consumption Increase (due to an increase in efforts for mixing and transport increase)
DM and C content reduction
C/N-ratio not changed
pH not changed
NH3, N2O and CH4 losses reduction
N losses reduction (if water-to-slurry-ratio is 2:1 or greater)
costs Increase (water, mixing, volume to be applied)
effort for slurry application reduction
fertilising effects not changed
Slurry additives can act on a chemical, physical or biological basis. Chemical-physical additives are
meant to adsorb NH4-N and thus reduce NH3 losses. However, this can only be achieved with high
amount of additives. For example, 25 kg of Zeolith per m3 slurry are necessary to adsorb 55 % of NH4-
N. On commercial farms it is neither possible nor economic to add such enormous amounts of slurry
additives.
Additives on an enzymatic basis shall increase biological degradation of organic matter with the aim to
reduce slurry dry matter content and thus avoid crust formation and sedimentation. In addition, odour
nuisance shall be reduced, as well.
Mode of action and composition of commercial additives are in most cases not known and it may be
questioned if the desired effects are achieved on commercial farms. Research has so far not been able
to proof significant effects of biological slurry additives. An increase in degradation of organic matter
during slurry storage improves slurry viscosity and reduces the potential for NH3 losses. However, as
organic matter is anaerobically degraded, potentials for CH4 emissions during storage increase.
Slurry aeration introduces oxygen into the slurry in order to allow aerobic microbes to develop.
Oxidation of organic matter to CO2 and H2O increases. Odorous compounds are degraded. Slurry dry
matter content decreases. Thus, less mixing is needed and technological properties of slurry are
improved. Successful aeration requires 200 m-3 oxygen per t of slurry (Burton 1998).
Slurry aeration results in an increase in NH3 emissions and in energy consumption. The potential for
N2O emissions is likely to increases, as well. The extent of these increases has so far not been exactly
quantified. This has to be done in order to allow a complete evaluation of slurry aeration (Table 14).
Table 14. Assessment of impacts achieved by slurry aeration
criteria result achieved by slurry aeration
energy consumption 3.6 - 17.6 kWh m-3(depending on slurry dry matter content)
DM and C content reduction
C/N-ratio not changed
pH increase
NH3, N2O and CH4 losses NH3: strong increase
N2O, CH4: unknown effect
N losses strong increase
costs 2.03 - 2.54 EURO m-3
effort for slurry application reduction
fertilising effects improvement
During slurry separation, solids are mechanically separated from slurry. This results in two fractions:
a liquid slurry fraction with low dry matter content and a solid fraction that can be stored in heaps.
Energy consumption for slurry separation is low. Dry matter content in the liquid fraction is reduced by
40 - 45%. Carbon content is reduced by 45-50 %. C/N-ratio decreases from about 10:1 to about 5:1
(Amon 1995). As carbon is removed from the slurry, microbial degradation of organic matter during
slurry storage is reduced.
The removal of solids reduces crust formation and sedimentation. Thus, less intensive mixing is
necessary to homogenise the slurry prior to application. Efforts for low emission application techniques
are reduced as separated slurry has a lower viscosity and flows more easily through band spreading
hoses. Slurries with low dry matter content can be spread with simple nozzle-beam-dischargers that can
be operated on slopes > 10 %, which is not possible with other band spreading techniques. Separated
slurry infiltrates rapidly into the soil. Thus, plants get less dirty and ammonia emissions after slurry
spreading are reduced. A reduction of ammonia emissions by slurry separation of up to 63 % is possible.
Separated slurry has a narrow C/N-ratio which reduces the potential for N immobilisation in the soil. N
availability is more predictable and can be better calculated in order to match nutrient requirements of
plants to fertilisation. Dosch (1996) investigated fertilisation with untreated and separated slurries. He
found significantly higher denitrification rates with untreated slurry. Separated slurry resulted in
significantly higher crop yield.
Slurry separation fulfils all requirements on manure treatment (Table 15). Costs for slurry separation
could be further reduced if the technology was more wide spread and more separators were built. As
fertiliser value of separated slurry is improved, mineral fertiliser input can be reduced. Slurry
application near the soil can be done with very simple low cost slurry spreaders.
Table 15. Assessment of impacts achieved by slurry separation
criteria result achieved by slurry separation
energy consumption cattle slurry: 0.10- 2.20 kWh m-3
pig slurry : 0.06 – 0.40 kWh m-3
DM and C content 40 – 45 % reduction
C/N-ratio reduction
pH not changed
NH3, N2O and CH4 losses reduction
N losses strong increase
costs 1.02 -2.03 EURO m-3
effort for slurry application reduction
fertilising effects improvement
Anaerobic digestion of animal manures is mainly implemented for energy production reasons.
Improvement of manure quality is a "by-product" of anaerobic digestion. Biogas production from
animal manures aims at maximising methane yield. Anaerobic degradation of organic substances is - in
contrast to other manure treatment options - not to be prohibited as far as possible, but to be enhanced.
Methane produced in an agricultural biogas plant is, however, not emitted into the atmosphere, but is
collected and transformed to electricity and heat in a combined heat and power coupling. Anaerobic
digestion not only reduces methane emissions from manure stores, but reduces consumption of fossil
fuels, as well. Both processes reduce anthropogenic greenhouse gas emissions.
Anaerobic digestion reduces manure carbon and dry matter content by about 50 % (Amon & Boxberger
2000). NH4-N content and pH in digested slurry are higher than in untreated slurry. Thus, potentials for
ammonia emissions during slurry storage are enhanced. Digested slurry has to be stored in covered
slurry stores that should be connected to the gas bearing system of the biogas plant, as methane is still
formed after the main digestion took place in the heated digester.
Due to the reduced dry matter content, biogas slurry can infiltrate more rapidly into the soil which
reduces ammonia emissions after slurry application. However, the increased NH4-N content and pH
give rise to higher ammonia loss potentials. It is to be recommended to apply biogas slurry with low
emission techniques near the soil surface. This considerably reduces ammonia emissions. N
immobilization and N2O losses are likely to be smaller than from untreated slurry. Energy consumption
for pumping and mixing is considerably reduced due to the reduced dry matter content. Anaerobic
digestion has multiple positive effects on environmental impacts of manure management (Table 16).
Table 16. Assessment of impacts achieved by anaerobic digestion
criteria result achieved by anaerobic digestion
energy consumption energy is produced
DM and C content up to 50 % reduction
C/N-ratio reduction
pH increase
NH3, N2O and CH4 losses reduction
N losses reduction (if low emission spreading techniques are applied)
costs for electricity production 0.15 - 0.20EURO kWh-1
effort for slurry application reduction
fertilising effects improvement
3.4.1 Conclusions, final remarks and research questions
It is clear that manure management impacts quantities of NH3, direct and indirect N2O emissions and
CH4 emissions at each stage of the manure management continuum (Chadwick et al. 2011). Since
production of these gases is of microbial origin, the DM content and temperature of manure and soil
are key factors in on farm manure management decisions that influence the magnitude of N and GHG
losses. There remains a degree of uncertainty in emission rates of N and GHG gases from different
stages of manure management, and researchers continue to investigate interactions of the management
and environmental factors which control emissions. Some specific approaches to reducing N and GHG
emissions from livestock housing and manure storage include optimising diet formulation, low emission
housing technologies, air scrubbers, manure storage outside the barn, cover of slurry stores, slurry
separation, and anaerobic digestion.
Some legislation may result in ‘win–win’ scenarios, such as the Nitrates Directive (91/676/EEC) which
has led to development of Nitrate Vulnerable Zone action plans to prevent application of (high available
N content manures slurry and poultry manure) in autumn, a practice which reduces N losses and direct
and indirect N2O losses. Whereas, other legislation may result in potential ‘pollution swapping’, as is
sometimes the case with use of slurry injection to reduce NH3 emissions at the expense of an increase
in N2O emissions. However, in this latter example there is no clear understanding of why this pollution
swapping only occurs on some occasions. The nature of the N cycle and its interaction with the C cycle
demands a holistic approach to addressing N and GHG emissions and mitigation research at a process
level of understanding. Systems based modelling must play a key role in integrating the complexity of
management and environmental controls on emissions. Progress has been made to this end (Sommer et
al., 2009), with some studies producing whole farm models encompassing livestock production (del
Prado et al., 2010). An evidence based database is required to validate and test such models to determine
the scope to which management practices can be used to reduce N and GHG from livestock manure.
The following research questions must be answered for an improvement of overall nitrogen efficiency:
Integrated concepts
relationship between nitrogen and GHG emissions
influence of climate change on nitrogen emissions
interaction between mitigation and adaptation measures
interaction between nitrogen emissions and animal welfare
integrated assessment of the whole manure management continuum
integrated assessment considering the three pillars of sustainability: economy, environment,
society
interaction between consumer demand and nitrogen emissions
development of region specific concepts for sustainable intensification
modelling of livestock production at regional, national and global scale
Detailed understanding at process level
assessment of emissions from naturally ventilated barns
assessment of emissions from new, animal friendly housing systems
development of mitigation measures esp. for naturally ventilated dairy barns (e.g. targeted
ventilation and air scrubber)
interaction between climate change and heat stress / animal behaviour / emissions
interaction between low protein diets and N and GHG emissions
life cycle assessment: grass based dairy feeding versus low protein dairy feeding
feed and manure additives for improved N use efficiency
manure treatment for maximum N use (increase of nutrient availability, decrease of emissions)
3.5 References
Aarnink, A. J. A. et al. (1996). Effect of slatted floor area on ammonia emission and on the excretory and lying
behaviour of growing pigs. Journal of Agriculture Engineering Research, vol. 64, pp. 299–310.
Amon, T., Boxberger, J. (2000). Biogas production from farmyard manure. In: Management Strategies for
Organic Wastes in Agriculture, FAO European Cooperative Research (ed.), Network on Recycling of
Agricultural, Municipal and Industrial Residues in Agriculture (RAMIRAN), 9th International Conference,
6 - 9th September 2000, Gargnano, Italy.
Amon, T. Boxberger, J. Gronauer, A. Neser, S. (1995). Einflüsse auf das Entmischungsverhalten, Abbauvorgänge
und Stickstoffverluste von Flüssigmist während der Lagerung. In: Bau und Technik in der
landwirtschaftlichen Nutztierhaltung, Beiträge zur 2. Internationalen Tagung am 14./15. März 1995 in
Potsdam. Institut für Agrartechnik Bornim, MEG, KTBL, AEL (eds), pp 91 – 98.
Beudert, B. Döhler, H. Aldag, R. (1988): Ammoniakverluste aus mit Wasser verdünnter Rindergülle im
Modellversuch. Schriftenreihe 28, VDLUFA, Kongreßband Teil II.
Bittman, S., Dedina, M., Howard C.M., Oenema, O., Sutton, M.A., (eds), 2014, Options for Ammonia Mitigation:
Guidance from the UNECE Task Force on Reactive Nitrogen, Centre for Ecology and Hydrology,
Edinburgh, UK.
Braam, C. R., J. Ketelaars and M. C. J. Smits (1997). Effects of floor design and floor cleaning on ammonia
emission from cubicle houses for dairy cows. Netherlands Journal of Agricultural Science, vol. 45, pp. 49–
64.
Braam, C. R., and others (1997). Ammonia Emission from a Double-Sloped Solid Floor in a Cubicle House for
Dairy Cows. Journal of Agricultural Engineering Research, vol. 68, No. 4 (December), pp. 375–386.
Broderick, G. A. (2003). Effects of Varying Dietary Protein and Energy Levels on the Production of Lactating
Dairy Cows. Journal of Dairy Science, vol. 86, pp. 1370–1381.
Burton, C.H. (1998). Processing strategies for organic wastes. In: Management strategies for organic waste use in
agriculture, Martinez, Jose (ed.), Abstracts of papers of 8th international conference of the FAO network
on recycling of agricultural, municipal and industrial residues in Agriculture.
Burton, C. H. (2007). The potential contribution of separation technologies to the management of livestock
manure, Livestock Science, vol. 112, pp. 208–216.
Canh, T. T., and others (1998). Dietary protein affects nitrogen excretion and ammonia emission from slurry of
growing-finishing pigs. Livestock Production Science, vol. 56, No. 5 (December), pp. 181–191.
Chadwick, D., Sommer, S., Thorman, R., Fangueiro, D., Cardenasa, L. Amon, B., Misselbrook, T. (2001). Manure
management: Implications for greenhouse gas emissions; Animal Feed Science and Technology 166– 167
(2011) 514– 531.
Dämmgen, U., Hutchings, N.J. (2008). Emissions of gaseous nitrogen species from manure management: a new
approach. Environ. Pollut. 154, 488–497.
del Prado, A., Chadwick, D., Cardenas, L., Misselbrook, T., Scholefield, D., Merino, P., 2010. Exploring systems
responses to mitigation of GHG in UK dairy farms. Agric. Ecosyst. Environ. 136, 318–332.
Denmead, O.T., Freney, L.R., J.R. (1982). Dynamics of ammonia volatilization during furrow irrigation of maize.
Soil Sci. Soc. Am. J., 46.
Dosch, P. (1996). Optimierung der Verwertung von Güllestickstoff durch Separiertechnik und
kulturartspezifische Applikationstechniken. Bayerisches Staatsministerium für ELuF, Gelbe Reihe,
Landtechnische Berichte aus Praxis und Forschung, No 56.
Ellen, H. H., and others (2008). Ammoniakemissie en kosten van chemische luchtwasser met bypassventilatoren
bij vleesvarkens (Ammonia emission and costs of a chemical air scrubber with bypass ventilation at a pig
house). Animal Sciences Group Report 151. Wageningen, the Netherlands: Wageningen University and
Research Centre. Available from http://edepot.wur.nl/35138.
Fangueiro, D., and others (2008a). Effect of cattle slurry separation on greenhouse gas and ammonia emissions
during storage. Journal of Environmental Quality, vol. 37, No. 6 (November) pp. 2322–2331.
Fangueiro, D., and others (2008b). Laboratory assessment of the effect of cattle slurry pre-treatment on organic
N degradation after soil application and N2O and N2 emissions, Nutrient Cycling in Agroecosystems, vol.
80, pp. 107–120.
Firestone, M.K., Davidson, E.A. (1989). Microbial basis of NO and N2O production and consumption in soil. In:
Andreae, M.O., Schimel, D.S. (Eds.), Exchange of Trace Gases between Terrestrial Ecosystems and the
Atmosphere. Wiley, New York, NY, USA, pp. 7–21.
Gilhespy, S. L., and others (2009). Will additional straw bedding in buildings housing cattle and pigs reduce
ammonia emissions? Biosystems Engineering, vol. 102, pp. 180–189.
Guingand N. (2009). Wet scrubber: one way to reduce ammonia and odours emitted by pig units. Paper presented
at the sixtieth meeting of the European Association for Animal Production, Barcelona, Spain, 24–27
August 2009.
Guingand, N., and V. Courboulay (2007). Reduction of the number of slots for concrete slatted floor in fattening
buildings: consequences for pigs and environment. In G. J. Monteny and E. Hartung, eds., Proceedings of
the International Conference on Ammonia in Agriculture: Policy, Science, Control and Implementation,
19–21 March 2007, Ede, Netherlands, pp. 147–148. Wageningen, the Netherlands: Wageningen Academic
Publishers.
Huynh, T. T. T., and others (2004). Effects of floor cooling during high ambient temperatures on the lying
behavior and productivity of growing finishing pigs. Transactions of the ASAE,15 vol. 47, No. 5, pp. 1773–
1782.
Melse, R. W., N. W. M. Ogink and B. J. J. Bosma (2008). Multi-pollutant scrubbers for removal of ammonia,
odor, and particulate matter from animal house exhaust air. In Proceedings of the Mitigating Air Emissions
from Animal Feeding Operations Conference, 19–21 May 2008, Des Moines, Iowa, United States of
America.
Melse, R. W., P. Hofschreuder and N. W. M. Ogink (2012). Removal of Particulate Matter (PM10) by Air
Scrubbers at Livestock Facilities: Results of an On-Farm Monitoring Program. Transactions of the
ASABE,16 vol. 55, pp. 689–698.
Melse, R. W., and N. W. M. Ogink (2005). Air scrubbing techniques for ammonia and odor reduction at livestock
operations: Review of on-farm research in the Netherlands. Transactions of the ASAE, vol. 48, pp. 2303–
2313.
Misselbrook, T. H., and J. M. Powell (2005). Influence of Bedding Material on Ammonia Emissions from Cattle
Excreta. Journal of Dairy Science, vol. 88, pp. 4304–4312.
Møller, H. B., J. D. Hansen and C. A. G. Sørensen (2007). Nutrient recovery by solid–liquid separation and
methane productivity of solids. Transactions of the ASABE, vol. 50, pp. 193–200.
Monteny, G. J. (2000). Modelling of ammonia emissions from dairy cow houses. PhD thesis, Wageningen
University, Wageningen, the Netherlands (with summaries in English and Dutch).
Ogink, Nico W. M., and Bert J. J. Bosma (2007). Multi-phase air scrubbers for the combined abatement of
ammonia, odor and particulate matter emissions. In Proceedings of the International Symposium on Air
Quality and Waste Management for Agriculture, Broomfield, Colorado, 16–19 September 2007. ASABE.
Available from http://elibrary.asabe.org/conference.asp?confid=aqwm2007.
Patterson, P. H., and Adrizal (2005). Management Strategies to Reduce Air Emissions: Emphasis — Dust and
Ammonia. Journal of Applied Poultry Research, vol. 14, No. 3 (Fall), pp. 638–650.
Powell, J. M., T. H. Misselbrook and M. D. Casler (2008). Season and bedding impacts on ammonia emissions
from tie-stall dairy barns. Journal of Environmental Quality, vol. 37, pp. 7–15.
Ritz, C. W., and others (2006). Improving In-House Air Quality in Broiler Production Facilities Using an
Electrostatic Space Charge System. Journal of Applied Poultry Research, vol. 15, No. 2 (summer), pp.
333–340.
Smits, M. C. J. (1998). Groeven maken in een dichte V-vormige vloer: enkele observaties naar loopgedrag en
ammoniakemissies (Grooving a solid V-shaped floor: some observations on walking behaviour and
ammonia emission). DLO18-IMAG19 Report P 98–60. Wageningen, the Netherlands.
Sommer, S.G., Olesen, J.E., Petersen, S.O., Weisbjerg, M.R., Valli, L., Rohde, L., Béline, F. (2009). Region-
specific assessment of greenhouse gas mitigation with different manure management strategies in four
agroecological zones. Glob. Change Biol. 15, 2825–2837.
Swensson, C. (2003). Relationship between content of crude protein in rations for dairy cows, N in urine and
ammonia release. Livestock Production Science, vol. 84, No. 2 (December), pp. 125–133.
Swierstra, D., C. R. Braam and M. C. J. Smits (2001). Grooved floor systems for cattle housing: ammonia emission
reduction and good slip resistance. Applied Engineering in Agriculture, vol. 17, pp. 85–90.
Webb, J., Misselbrook, T.H. (2004). A mass-flow model of ammonia emissions from UK livestock production.
Atmos. Environ. 38, 2163–2176.
Whitehead, D. C. (2000). Nutrient Elements in Grassland: Soil-Plant-Animal Relationships. Wallingford, United
Kingdom: CABI Publishing.
Ye, Z. Y., and others (2008a). Influence of airflow and liquid properties on the mass transfer coefficient of
ammonia in aqueous solutions. Biosystems Engineering, vol. 100, No. 3 (July), pp. 422–434.
Ye, Z. Y., and others (2008b). Ammonia emissions affected by airflow in a model pig house: effects of ventilation
rate, floor slat opening and headspace height in a manure storage pit. Transactions of the ASABE, vol. 51,
pp. 2113–2122.
Zhao, Y., and others (2011). Effectiveness of multi-stage scrubbers in reducing emissions of air pollutants from
pig houses. Transactions of the ASABE, vol. 54, pp. 285–293.
4 Housed livestock, manure storage, manure
processing: working group report
Author: Barbara Amon
The following chapter builds upon the “Housed livestock, manure storage and manure processing:
background document (chapter 3)”, and provides a summary of discussions held during the workshop
by the working group for this theme.
4.1 Housing
The Guidance document shall give general information on housing systems
detailed descriptions of housing systems in the Annex and / or in link to already existing
documents (e.g. pig & poultry in the IPPC BREFR document, NH3 in the UNECE GD
document)
Slurry versus FYM systems
o Describe what happens in the system
o Describe the pro’s and con’s
o assessment must cover the whole chain
Detailed description of housing systems exists for pig and poultry and is lacking for cattle.
There is a need to compile the current state of the art of housing systems and emissions from
cattle houses
Ventilation is an important issue (most important for cattle), but more research is needed on
o influence on ventilation on emission rates
o targeted ventilation for optimum barn climate and low emissions
Only limited information available on N2O and hardly any on N2 emissions => lack of research
collate UNECE + IPCC; check for possible synergies or antagonisms
Check airscrubbers / biofilters for their impact on NH3 + N2O + N2;
give guidance on best practice management of airscrubbers / biofilters
Outside yard: may elevate NH3 emissions
o give guidance on management
o possible conflict between animal welfare and NH3
Measures in housing often less easily applicable than storage and spreading, because houses
have to be newly built or retro-fit
GD on integrated N management shall distinguish short / medium / long term measures
Urease activity: use floors with less urease activity (e.g. metal floors)
Acidification in the house reduces NH3 and CH4 emissions
General principle: reduce slurry pH
General principle: urine – faeces separation urease activity down
Dilution with water: lower NH3 emissions, but increases costs, water consumption, storage &
application volume
4.2 Livestock Feeding
Improve N retention, decrease N input, Data on reduction of N excretion are available
Breeding can also be a measure, more research needed
With cattle:
Consider possible side effects on methane emissions
Priority should be given to conversion of roughage to high value products
region specific concepts are required
With pigs:
Feeding is well developed
Further reduction lead to elevated costs (artificial amino acids)
4.3 Treatment
4.3.1 Aims of manure treatment
increase fertiliser value of manures
reduce emissions to air and water
4.3.2 Slurry treatment
anaerobic digestion: CH4 reduced, TAN and pH increased => improved fertiliser value, but low
emission application technologies are required
co-digestion required for economic reasons
slurry should go directly to the digester
ammonia liquor NH3 stripping? Struvite?: more research and literature review required
slurry separation: do it after AD,
o liquid fraction CH4 and NH3 and N2O reduced
o solid fraction? contradictory results on emissions, proper management required, take
measures to lower emissions from solid storage
FYM: transport to arable regions possible, export of nutrients possible
FYM: suitability varies across Europe, e.g. Spain: three harvests per year, low carbon in the
soil, apply FYM directly, crust forms immediately on a FYM heap (heat!), hardly any emissions
composting requires sophisticated, well advanced technology, higher risks for elevated
emissions during the composting process
Manure treatment plants (e.g. membrane technologies): results from Life project in Italy
become available in 2017
open questions: what manure treatment solutions are available and economically feasible for
small farms?
4.3.3 Storage
Slurry shall be moved to a cool outside storage to keep NH3 and CH4 emissions down
Cover of stores is required (see GD and springer book on ammonia abatement) and
Influence of the crust is unclear, more research is needed
Effect on N2O formation?
Effect on CH4 oxidation?
Include guidance on how to cover manure stores and lagoons (i.e. technology and management)
Efficiency of crust depends on the region / climate / water through rain
Italy uses larger storage bags in replacement of lagoons
Low tech covers can be implemented as short term measures
efficient covers should be used for newly built stores in the medium and long term
4.4 N guidance document
4.4.1 Aspects of N guidance document
Forms of N to be covered:
NH3, NH4, NO3, N2O,
N2, NOx, Norg
Develop N flux model including pictures ((some countries already have this)
A document on integrated N management should link to a range of aspects of sustainable land
management, including:
o CH4
o energy use
o water consumption
o cost / economy
o animal welfare and health
o livestock density; amount of N surplus
o productivity
o consumer demand
o outside framework conditions (e.g. financial conditions, political conditions)
o region specific and flexible concepts
o agronomic conditions
o measures for different climates
o landscape
o biodiversity
o farm structure
N guidance requires detailed activity data
5 Field application of organic and inorganic
fertilizers: Background Document
Authors: Tom Misselbrook, Shabtai Bittman, Claudia Cordovil, Bob Rees, Roger Sylvester-Bradley,
Jørgen Olesen, Antonio Vallejo
The following chapter provides an overview of field application of organic and inorganic fertilizers,
and was used as a background document by the “Field application of organic and inorganic fertilizers
working group”.
5.1 Types and quantities of materials being applied
Nitrogen is applied directly to agricultural land as a crop nutrient in the form of manufactured inorganic
fertilizers, as livestock manures or as other organic amendments deriving from waste or by-products
(e.g. sewage sludge, digestate from anaerobic digestion, composts). Managed land will also receive
nitrogen inputs more indirectly from recycling of crop residues, from dung and urine deposition by
grazing livestock and through N fixation by legumes. Together, these direct and indirect inputs total
approximately 25,000 Gg N per year for the EU28 (Figure 13). In addition to this is a further 2,000 Gg
N per year input from atmospheric deposition but management of that is considered outside the scope
of this background document. The characteristics of these different sources of N and their management
are important in determining the agronomic value to crop and forage production and potential
environmentally damaging impacts.
Figure 13. Estimate of N inputs to agricultural soils for EU28 (Gg N yr-1) for 2014.
43%
19%
2%
20%
12%
4%
Mineral fertilizer
Manure applied
Other organics applied
Crop residues
Grazing returns
Biological N fixation
10,875
4,765
615
4,985
3,160
1,000
25,400Total
Gg N yr-1
Values derived from the 2016 GHG inventory submission to UNFCCC by the European Union (http://unfccc.int/national_reports/annex_i_ghg_inventories/national_inventories_submissions/items/9492.php) with the
exception of Biological N fixation which was derived from Leip et al. (2011a) for the year 2002.
5.1.1 Inorganic mineral fertilizers
Manufactured inorganic mineral fertilizers represent the largest category of N inputs to agricultural land
in the European Union (Fig. 1). There are a number of different formulations and blends of N-containing
fertilizers used in Europe but these can be broadly considered to deliver nitrogen in the chemical form
of ammonium, nitrate or urea. Ammonium and nitrate are directly available for plant uptake, although
ammonium will also convert to nitrate in the soil through the microbial process of nitrification. These
two forms of N will behave differently in the soil, with ammonium more susceptible to losses via
ammonia volatilization while nitrate is more susceptible to losses via denitrification and leaching. Urea
hydrolyses after application to form ammonium (and subsequently nitrate); the hydrolysis process is
associated with an increase in pH which greatly increases the susceptibility to losses via ammonia
volatilization. Straight N fertilizer products include ammonium nitrate (AN), calcium ammonium
nitrate (CAN), urea and urea ammonium nitrate (UAN, a liquid formulation). Anhydrous ammonia is a
liquid (gas under pressure) fertilizer that special equipment and safety measures for application.
Combinations with other nutrients include ammonium sulphate, diammonium phosphate and potassium
nitrate. Ammonium nitrate and CAN represent the major fertilizer forms used in Europe, with urea
(either as urea or UAN) accounting for approximately 17% of total fertilizer N use in the EU28 in 2014
(based on background data supplied with the 2016 European Union GHG submission to the UNFCCC).
Other nitrogen fertilizers including inhibitors and slow release formulations are discussed in Section
6.1.
5.1.2 Livestock manures
The major livestock types for which managed manure is applied to land are cattle (dairy and beef), pigs
and poultry. Nitrogen will be present in organic and inorganic (ammonium and nitrate and, for poultry,
uric acid and urea) forms. Manure characteristics depend on livestock diet and performance, housing
and storage systems (including bedding use) and any subsequent processing prior to land application.
For cattle and pigs, manure type can be categorized as either slurry, consisting of mixed urine, faeces
and water with very little bedding material and with a dry matter content typically in the range 1-10%,
or as farm yard manure (FYM) consisting of urine and faeces mixed with large amounts of bedding
material (typically straw) having higher dry matter content. Slurries will typically contain 40-80% of
the N in the ammonium form with the remainder as organic N and none as nitrate. Farm yard manure
typically contains a much lower proportion of the N in the ammonium form and may contain a small
fraction in the nitrate form. Pig manure will typically have a higher total N and available (mineral) N
content than cattle manure but this depends on water content.
For poultry, manure can generally be categorized as litter, deriving from systems where excreta are
mixed with bedding (e.g. broiler houses) or as manure where excreta are collected, generally air-dried,
without bedding material. Both have relatively high dry matter contents (>30%) and higher total N
contents than cattle or pig manures. Between 30-50% of the total N may be in an inorganic form as uric
acid or ammonium.
Manures will also vary regarding the content of other nutrients and application rates of all manures may
be limited by the concentration of phosphorus (P) rather than N. The mineralization, availability and
utilization of manure N is strongly influenced by C:N ratio.
5.1.3 Other organic N amendments
A range of other N-containing organic amendments are applied to agricultural land and while the total
applied is currently small, this is likely to increase (and be encouraged) as the concept of the circular
economy becomes more prevalent. These materials may be liquids (e.g. digestates) or solids (e.g.
composts), deriving from human wastes, food processing, green wastes, etc., and for the purposes of
this background document they will be implicitly included in discussions regarding management of
livestock manures. Even though this recycling is important for the overall sustainability of society, the
additional N added to agricultural systems are likely to be small compared to manure and fertiliser
inputs. However, processing such organic amendments (e.g. anaerobic digestion) may increase the plant
availability of N.
5.1.4 Crop residues
The quantity of N returned to agricultural soils through crop residues is of a similar magnitude to that
applied as livestock manures (Fig. 1). These will include above and below ground residues, the N
content of which will depend largely on crop type, yield and fertilizer management. The N will be
almost entirely in an organic form, the rate of mineralization of which will depend on a number of crop,
soil and environmental factors, and the potential for N losses will be mostly through nitrate leaching
and denitrification rather than ammonia volatilization. In some cases (e.g. for high C residues) N from
residues will be stored in soils as organic matter.
5.1.5 Grazing returns
Cattle and sheep can spend a substantial proportion of the year at pasture grazing depending on regional
soil and climate characteristics and management systems. During grazing, dietary N not retained by the
animal is deposited directly back to the pasture as dung and urine. Dung contains mostly organic N
forms, which will subsequently mineralize at a rate dependant on soil and environmental factors,
whereas N in urine is predominantly in an inorganic form and immediately susceptible to losses via
ammonia volatilization, leaching and denitrification (Selbie et al., 2015).
5.1.6 N fixation
Cultivated legumes are grown on a relatively small proportion of the European Union agricultural area
and their production in Europe has been declining over several decades despite an increased reliance by
Europe on imported grain legumes (Luscher et al., 2014). This somewhat paradoxical situation
contributes to global imbalances in protein production and consumption and the EU is currently
considering options to increase home grown legumes to reduce the reliance on imported protein
predominantly for livestock feed. Clover is an important constituent in many grasslands across Europe
but the quantity of N provided by pasture is highly uncertain. During the growing season, N fixed by
legumes will be mostly utilized by the crop (legume or companion crop) but when active growth slows
or ceases then fixed N may be released to the soil through mineralization with potential subsequent
losses through leaching and denitrification, in particular if the grassland is ploughed as part of a rotation
system.
The FP7 project Legume Futures recently estimated that biological N fixation in Europe provided an
input of 0.81 Mt N fixed in EU27 in 2009 (225 kt N from grain legumes and 586 kt N from grassland
which was broadly similar to the mean estimate of 1.12 Mt from four European N budget models (de
Vries et al., 2011) and the value of 1.1 Mt submitted to the United Nations Framework Convention on
Climate Change (EEA, 2008). Most of the difference occurs because the N budget models allow for
~5 kg ha-1 of N fixation by free-living microbes in all non-legume arable land, in contrast to the Legume
Futures focus on legumes
5.1.7 Current estimates of Nitrogen losses
Figure 14. Estimates of N losses from agricultural soils in EU28 (Gg N yr-1) for the year 2014.
Values derived from the 2016 GHG inventory submission to UNFCCC by the European Union
(http://unfccc.int/national_reports/annex_i_ghg_inventories/national_inventories_submissions/items/9492.php) with
the exception of NOx and N2 emissions which were estimated as a ratio of reported N2O emission based on values given
by Leip et al. (2011a).
Estimates of N losses from agricultural soils for the EU28 are given in Figure 14, based on the 2016
European Union GHG submission to UNFCCC for ammonia, nitrous oxide and leaching and runoff
losses and using the ratio of NOx and N2 to N2O emissions for 2002 as reported by Leip et al. (2011a)
to derive revised NOx and N2 emission estimates for 2014. These loss estimates are subject to large
uncertainties, but imply that approaching 50% of N inputs to agricultural soils in the EU28 (including
the estimate for atmospheric deposition) are subsequently lost to the environment through gaseous
emissions, leaching and runoff. Of this, almost half is via leaching and run-off and another third as
dinitrogen via denitrification. Dinitrogen is environmentally benign, but this represents a large loss of
N which otherwise would have enabled agricultural N inputs to be reduced with subsequent savings in
other parts of the system.
16%
3%0%
32%
49%
NH3 emission
N2O emission
NOx emission
N2 emission
Leaching and runoff
2,075
350
75
4,100
6,365
12,965Total
Gg N yr-1
Emissions of ammonia, nitrous oxide and particularly NOx account for smaller proportions of the total
N loss from agricultural soils, but magnitude of loss doesn’t necessarily equate with magnitude of
impact. For nitrous oxide and ammonia, agricultural soils represent one of the most significant emission
sources and therefore a key target area for interventions to meet national and international emission
reduction targets.
5.1.8 Spatial distribution across Europe
Nitrogen inputs to agricultural soils vary considerably across Europe according to locations of livestock
and crop areas and specific management practices, as driven by underlying factors including soils,
climate and socioeconomics, as well as governance systems that regulate N inputs at farm scale. Mineral
N fertilizer inputs tend to be higher across broad areas of NW Europe, while manure N inputs are more
localised to areas with high livestock densities with particular ‘hotspots’ in the Netherlands and N Italy
for example due to cost of transporting the manures (Figure 15; NB data shown for 2005). Finely
distributed N input estimates across space will have a greater level of uncertainty than national- or
European-scale estimates and will vary across the region, particularly for manure N inputs where robust
data on spatial variation in key factors influencing livestock N excretion (diet, management) and
subsequent manure management practices may not be available.
Figure 15. Estimates of spatial distribution of mineral fertilizer and manure N to agricultural land for 2005 (Bouraoui
et al., 2009.).
Spatial distribution of the different N losses across Europe relies on modelling, which can be performed
at different complexities. At the simplest, national N loss estimates can be spatially distributed using
nationally averaged emission factors (e.g. per livestock head or per kg of fertilizer N) according to
national survey data on livestock numbers, cropping and fertilizer use. More informatively, empirical
or process-based models can be used which reflect the spatial (and temporal) distribution in underlying
factors driving the loss processes (soils, climate) and therefore better reflect spatial distribution of
losses, albeit with uncertainties associated with required parameters and data inputs and model accuracy
and performance. Such an approach will result in different ‘emission factors’ for different regions (and
different nationally-averaged emission factors). For example, Leip et al. (2011b) used the DNDC-
Europe model to derive spatially distributed nitrous oxide emission factors across Europe and showed
that while on average the default IPCC emission factor (1% of applied N being emitted as N2O-N) was
appropriate across Europe, spatial variability was large with national averaged emission factors ranging
from 0.4 to 4.1%.
Similarly, there is currently significant uncertainty around the ammonia emission factor for urea
fertilizer application to land, with the EMEP/EEA Air Pollutant Inventory Guidebook of 2009 giving
an emission factor relating to the average spring temperature, but a subsequent revision in the 2013
Guidebook removing the temperature dependence and giving a default emission factor for urea of 24.3%
of applied N being lost as ammonia-N. This implied a very large change in ammonia emission estimates
for countries with lower spring temperatures (e.g. Germany) with potential consequences regarding
compliance with agreed national emission ceiling targets. Further Guidebook revision is ongoing, with
an expected return to a process-model approach able to reflect regional differences. However, European
countries may apply different approaches in their national inventory models depending on the data they
have available, from a Tier 1 approach which applies a default emission factor to all fertilizer N
regardless of type, through Tier 2 which reflects fertilizer type in emission factor, to Tier 3 where a
country can use its own measurement data or apply a more detailed model. This highlights the
importance of having, and using a robust understanding of the N loss processes when compiling
estimates of the different loss pathways and of using a consistent approach across all regions, despite
different contexts and activity data.
Finally, the impacts of N losses from agricultural soils on the environment will also have a spatial
dimension. A large proportion of ammonia emissions from N applied to agricultural soils will be
redeposited locally, with potential impacts through eutrophication and acidification, but a proportion
will also be subject to longer range transport and processes associated with aerosol formation with
subsequent human health implications. Similarly, N losses through leaching and runoff will have a
local, catchment and potentially regional effect on water quality depending on flow pathway and N
transformation and reduction processes along this pathway. For these reactive N species therefore, a
good understanding of source-receptor matrices is required including appropriate spatial and temporal
distributions. In contrast, nitrous oxide has a global, rather than local impact as a greenhouse gas and
dinitrogen is environmentally benign. For these gases an understanding of the spatial and temporal
influences on their emissions is important, but such influences on dispersion and impacts need not be
considered.
5.1.9 Management practices and influence on N losses
Nitrogen is the nutrient recovered in largest quantities from soil by agricultural crops, and the
availability of nitrogen to crops has a major impact on yields. Management of the different N inputs to
agricultural soils will influence the subsequent N cycling, N utilisation by crops and losses of N in
different forms to the environment. Until now, focus has largely been on controlling individual N loss
pathways – e.g. nitrate leaching (Nitrates Directive), ammonia (Gothenburg Protocol, NECD and
Habitats Directive) and nitrous oxide (Kyoto protocol) and guidance given accordingly (e.g. TFRN
Options for Ammonia Mitigation Guidance document). It is critical in trying to develop a more joined-
up approach to N guidance to have a good understanding of how management practices and targeted
mitigation measures might impact on the whole N cycle and not just one specific pathway. This section
presents briefly the main management practices that will influence N utilization and losses from the
different N sources. A summary of the impacts on the different N losses is given in Appendix 1.
Additionally, the concept of precision agriculture for enhanced Nitrogen use efficiency is very relevant
here and complements the management practices discussed. Enhancing N use efficiency is not only a
question of proper fertilisation strategies, it also is also very much related maintaining a health crop,
where good soil quality, good crop establishment and proper control of weeds, pests and diseases play
major roles.
5.1.10 Inorganic mineral fertilizers
Use of fertilizer N commonly doubles crop yields, and the longer term economic benefits of N fertilizer
use are even larger because fertilizer N serves to build soil fertility. Thus fertilizer N is vital to the
profitability of crop production in all regions of the EU and N fertilizers are used by almost all farms
other than those committed to ‘organic’ production.
Quantities of N required by crops (and used) are crudely related to their productivities. Thus productive
crops need more N, whilst crops with short life-cycles or subject to drought need less N. Whilst plant
breeding and improved agronomy have increased the efficiency of crop N use a little, most attempts to
increase crop productivity are nevertheless also associated with increased N requirements (Sylvester-
Bradley & Kindred, 2009). Best responses to fertiliser N are generally through application in spring,
just prior to rapid crop growth, whilst soils are usually drying (evapotranspiration exceeding rainfall).
Thus most gaseous losses occur soon after application but most leaching losses are delayed until after
harvest; they arise from fertiliser N that has been immobilized (partly in crop residues) and re-
mineralized. This legacy of immobilized N, especially from inefficient crops, tends to build soil fertility
and reduce N requirements of succeeding crops (Sylvester-Bradley, 1996).
Guidance on N application rates and timings is often available at a national level (e.g. UK RB209) but,
due to local factors and conditions including soil, weather, disease incidence etc, recommendations are
generally imprecise with, at best, half of them differing by more than 50 kg/ha from the true optimum
(Sylvester-Bradley et al., 2008). However, N losses relate better to absolute amounts applied than to
imprecision, so they could be reduced more by improving fertiliser efficiencies or targeting for lower
crop N contents (e.g. protein concentrations) than by than improving fertilizer recommendations.
Inhibitors can be incorporated into fertilizer products to reduce specific N loss pathways and improve
efficiency (Abalos et al., 2014). Urease inhibitors used with urea fertilizer products are very effective
at reducing ammonia emissions, and generally give an associated enhancement in crop yield, although
the potential for nitrous oxide emissions (and nitrate leaching) may be marginally increased as more
available N is retained in the soil. Nitrification inhibitors used with urea and ammonium based fertilizers
can be very effective at reducing nitrous oxide emissions, although efficacy varies according to soil and
weather conditions. Positive impacts on crop yields have been more difficult to show, and there is a
potential increase in ammonia emission. The use of double inhibitors with urea-based fertilizers has
been trialled to reduce all losses and improve N utilization with mixed results (e.g. Harty et al., 2016;
Zaman et al., 2009).
5.1.11 Livestock manures
There has been considerable research and development of slurry application methods associated with
lower ammonia emissions than surface broadcast application and these methods are well established,
even if not well implemented across Europe. Impacts of these methods on other N pathways is perhaps
less well established, with mixed evidence regarding increases in nitrous oxide emissions and benefits
of ammonia emission reduction not always being apparent in higher crop yields or N uptake. A recent
review showed that nitrous oxide emissions can range between 0.1-9.5% of the total N contained in the
slurry, with this range being affected by slurry type, application method, soil conditions and climate
(Chadwick et al., 2011). The use of trailing shoe and injection technology can dramatically reduce
ammonia emissions and odour and thus reduces indirect nitrous oxide emissions. However, studies have
shown that such techniques increase direct nitrous oxide emissions (Bourdin et al., 2014; Thorman et
al., 2007). A recent comparison between splash plate and injection techniques in Ireland concluded that
there was no significant difference in net greenhouse gas emissions from the two techniques (Bourdin
et al., 2014). Slurry acidification as a means of reducing ammonia emissions is also very effective and
in recent years has been demonstrated to be a practical option with significant implementation in
Denmark. Effects on crop yields have generally shown to be positive, but longer term impacts on soil
quality across the range of European soils and conditions still need further investigation.
Slurry dilution and application through fertigation in areas where irrigation is required is another option
aimed at reducing ammonia emissions, through more rapid soil infiltration and, while the potential for
nitrous oxide and nitrate leaching is to increase the risk of this is low if applied at agronomically sensible
times and rates. Pre-processing, such as slurry separation, may also improve the ability to use the slurry
nutrients more efficiently, but impacts on N flows will depend on the subsequent use of the liquid and
solid fractions.
Rapid soil incorporation of manures by tillage significantly reduces ammonia emission, again with the
potential to increase nitrous oxide emissions and nitrate leaching depending on timing and conditions.
There is some discussion regarding practicalities of rapid incorporation, and what time period is
considered ‘rapid’, and monitoring compliance of such a measure may present difficulties.
Nitrification inhibitors can be used to reduce direct nitrous oxide emissions and nitrate leaching
associated with manure application to land, but have the potential to increase ammonia emissions and
positive effects on yield or crop N uptake are small if seen at all.
Part of the N in manure is applied in organic form, which is not readily available for plant uptake, and
which through mineralisation may enhance leaching losses outside of the main crop growing season.
Anaerobic digestion of manures enhances the proportion of mineral (ammonium) part of the liquid
manure, which enhances crop N uptake and reduces N leaching. However, anaerobic digestion also
results in higher slurry pH which may increase ammonia volatilisation during storage and after
application. The enhanced volatilisation of the digested slurry is to some extent mitigated by a more
rapid infiltration into the soil due to changes in viscosity.
The focus for integrated guidance should therefore be on maximizing manure N (and nutrient)
utilization through development of a nutrient management plan including fertilizer use depending on
crop requirements, considering application rate, timing and method according to local soil and
environmental conditions.
5.1.12 Legumes and crop residues
Leguminous crops input N to agricultural systems by biological N fixation, in which a symbiotic
relationship is formed between the legume and N-fixing bacteria. Fixation (compared with mineral
fertilizer use) is associated with reduced GHG emissions for two reasons; firstly, emissions from N
manufacture are avoided, and secondly, the process of N fixation itself is associated with an emission
factor of 0 (IPCC 2006), unlike inorganic N fertilisers. For grassland systems the challenge is to
maintain an appropriate proportion of clover in the sward within a season and across multiple seasons
and manage mineral N fertilization to achieve an optimal delivery of fixed N to the mixed sward. Crop
residues are known to contribute to both nitrous oxide and ammonia losses, although this is related to
residues quality, environmental conditions and method of incorporation. Recent research suggests that
nitrous oxide emissions from crop residues may be lower than previously thought (Sylvester-Bradley
et al., 2015). Management considerations should include the avoidance of high available soil mineral N
contents when crop uptake is low.
Winter cover crops are used in some circumstances to minimize high soil available mineral N content
over the high risk period for nitrate leaching but their success in increasing N use efficiency over the
whole cropping cycle depends on effective management of the cover crop residue. Tillage options
influencing N mineralisation will impact on potential N losses and uptake. In colder climates, freeze
thaw cycles over the winter period can cause significant nutrient release and nitrous oxide emissions.
In order to minimise N loss it is necessary to time tillage operations in order to optimise synchrony
between N release and uptake by a subsequent crop N uptake.
5.1.13 Grazing returns
The management of grazing livestock and the impact of the N returns through dung and urine can be of
significant importance for countries where there is a high reliance on grazing to feed ruminants (e.g.
Ireland, UK). The key management tool available to influence soil N losses from grazing is to remove
grazing animals prior to periods of high risk of N loss (via leaching and denitrification), i.e. having a
shorter grazing period than consideration of soil condition and herbage availability alone would suggest.
However, this has to be weighed against the implications for N flows occurring during the housing of
the livestock, where ammonia emissions are likely to be greater. The use of appropriate forage species
and fertilizer management to optimize the feed quality for the grazing animal will improve N utilization
and reduce N excretion. Information on the influence of different grazing practices (set stocking,
rotational paddock grazing, mob grazing) on herbage N utilization, N excretion and N losses is required
to develop guidance on improved N use at the system level. The use of nitrification inhibitors to
specifically reduce nitrous oxide emissions and nitrate leaching associated with urine patches represents
another management tool for which cost-effective delivery mechanisms need to be developed and the
issues of inhibitor retention in milk or meat need to be addressed.
5.1.14 Nitrogen use efficiency and precision management
The EU Nitrogen Expert Panel (2015) have introduced the concept of a target range for N use efficiency
taking into account a minimum level of desired productivity, a desired maximum N surplus (per ha)
and an acknowledgment that long-term mining of soil N reserves is unsustainable (Figure 16). The N
output target must take into account both quantity and quality of product, whether that be food or feed,
so that N is not wasted in a later part of the food production/consumption chain. This targeting of
optimal N use efficiency might provide a starting framework for joined-up Nitrogen guidance for food,
air, water and climate co-benefits. The concept of precision agriculture is very relevant to this,
understanding the importance of all other factors being right (other macro-and micro-nutrient supply,
water supply, soil ‘health’, management of pests and diseases) in order to achieve optimal N use
efficiency.
Historically most fertiliser recommendation systems in Europe have taken little account of spatial
variability in N cycling processes, despite the well established heterogeneity of N cycling processes
within landscapes. Our rapidly developing ability to observe and analyse spatial and temporal
heterogeneity of plant and soil condition, coupled with information and sensor technologies that are
able to manage fertiliser, lime and tillage operations on a more spatially explicit basis are beginning to
offer opportunities to develop precision N management. Optimising the use of such technologies will
depend upon a further development in understanding of underlying soil processes, but offers the
potential to deliver increased N use efficiency in agricultural systems {Diacono, 2013}. However,
recent research shows that, so far, the imprecisions that apply at a field-scale, also apply at a sub-field
scale (Kindred et al., 2015).
Figure 16. Conceptual framework of the N use efficiency (NUE) indicator (EU Nitrogen Expert Panel, 2015)
5.1.15 Water and N use efficiency
Water is a driver of the main environmental problems caused by excessive N inputs (mineral or organic
fertilizers) in agroecosystems. Excessive water input, either by rain or irrigation, enhances nitrate
contamination of water bodies or increases emissions of nitrous oxide. Therefore, sustainable
intensification of agriculture should take into account management strategies towards increasing water
and N use efficiency simultaneously.
In irrigated agriculture, water application is a management option that the farmers may use to enhance
NUE and reduce losses (Quemada and Gabriel 2016). In this sense, new techniques such fertigation
have great potential for increasing N use efficiency of fertilizers. Fertigation is a particular case of
scheduled irrigation combined with nutrient application. In conventional fertilization the fertilizer is
split in one, two or three applications. During a certain period, there is an excess of N in soil that could
reduce NUE. With fertigation the fertilizers are dissolved and supplied with irrigation. The number of
applications can be high and adapted to crop demand, therefore reducing N potential lost (Abalos et al
2014).
5.2 References
Abalos, D., Jeffery, S., Sanz-Cobena, A., Guardia, G., Vallejo, A. (2014). Meta-analysis of the effect of urease
and nitrification inhibitors on crop productivity and nitrogen use efficiency. Agriculture, Ecosystems
and Environment 189, 136-144.
Abalos, D., Sanchez-Martín, L., García-Torres, L., van Groenigen, J.W., Vallejo, A. (2014). Management of
irrigation frequency and nitrogen fertilization to mitigate GHG and NO emissions from drip-fertigated
crops. Science of the Total Environment 490, 880-888.
Bourdin, F., Sakrabani, R., Kibblewhite, M.G., Lanigan, G.J. (2014). Effect of slurry dry matter content,
application technique and timing on emissions of ammonia and greenhouse gas from cattle slurry
applied to grassland soils in Ireland. Agriculture, Ecosystems & Environment 188, 122-133.
Bouraoui F., Grizzetti B., Aloe, A. (2009). Nutrient discharge from rivers to seas. JRC EUR 24002 EN, 72pp.
Chadwick, D., Sommer, S., Thorman, R., Fangueiro, D., Cardenas, L., Amon, B., Misselbrook, T. (2011).
Manure management: Implications for greenhouse gas emissions. Animal Feed Science and
Technology 166-67, 514-531.
De Vries, W., Leip, A., Reinds, G.J., Kros, J., Lesschen, J.P. & Bouwman, A.F. (2011b). Comparison of land
nitrogen budgets for European agriculture by various modeling approaches. Environmental Pollution
159, 3254-3268.
EEA (2008). Annual European Community Greenhouse Gas Inventory 1990-2006 and Inventory Report 2008.
UNFCCC Secretariat, European Environment Agency.
EU Nitrogen Expert Panel (2015) Nitrogen Use Efficiency (NUE) - an indicator for the utilization of nitrogen in
agriculture and food systems. Wageningen University, Alterra, PO Box 47, NL-6700 Wageningen,
Netherlands. Available online at www.eunep.com
Fangueiro, D., Surgy, S., Fraga, I., Vasconcelos, E., Coutinho, J. (2015). Acid treatment of animal slurries:
potential and limitations. International Fertiliser Society Proceedings 775.
Harty, M.A., Forrestal, P.J., Watson, C.J., McGeough, K.L., Carolan, R., Elliot, C., Krol, D., Laughlin, R.J.,
Richards, K.G., LAnigan, G.J. (2016). Reducing nitrous oxide emissions by changing N fertiliser use
from calcium ammonium nitrate (CAN) to urea based formulations. Science of the Total Environment
563-564, 576-586.
Kindred, D.R., Milne, A.E., Webster, R., Marchant, B.P., Sylvester-Bradley, R. (2015). Exploring the spatial
variation in the fertilizer-nitrogen requirement of wheat within fields. The Journal of Agricultural
Science 153, 25-41.
Leip et al 2011 European Nitrogen Assessment
Leip, A., Busto, M. Winiwarter, W. (2011). Developing spatially stratified N2O emission factors for Europe.
Environmental Pollution 159, 3223-3232.
Luscher, A., Mueller-Harvey, I., Soussana, J.F., Rees, R.M., Peyraud, J.L. (2014). Potential of legume-based
grassland-livestock systems in Europe. Grass and Forage Science 69, 206-228.
Quemada, M., Gabriel, J.J. (2016). Approaches for increasing nitrogen and water use efficiency simultaneously.
Global Food Security 9, 29-35.
Selbie, D.R., Buckthought, L.E., Shepherd, M.A. (2015). The challenge of the urine patch for managing
nitrogen in grazed pasture systems. Advances in Agronomy 129, 229-292.
Sylvester-Bradley, R., Kindred, D.R. (2009). Analysing nitrogen responses of cereals to prioritize routes to the
improvement of nitrogen use efficiency. Journal of Experimental Botany 60, 1939-1951.
Sylvester-Bradley, R. (1996). Adjusting N applications according to N applied for the last crop. Aspects of
Applied Biology, Rotations and Cropping Systems 47, 67-76.
Sylvester-Bradley, R., Kindred, D.R., Blake, J., Dyer, C.J., Sinclair, A.H. (2008). Optimising fertiliser nitrogen
for modern wheat and barley crops. Project Report No. 438, HGCA, London. 116 pp.
Sylvester-Bradley, R., Thorman, R.E., Kindred, D.R., Wynn, S.C., Smith, K.E., Rees, R.M., Topp, C.F.E.,
Pappa, V.A., Mortimer, N.D., Misselbrook, T.H., Gilhespy, S., Cardenas, L.M., Chauhan, M., Bennett,
G., Malkin, S., Munro, D.G. (2015). Minimising nitrous oxide intensities of arable crop products
(MIN-NO). AHDB Project Report No. 548. Pp. 228.
Thorman, R., Sagoo, E., Williams, J.R., Chambers, B.J., Chadwick, D.R., Laws, J.A., Yamulki, S. (2007). The
effect of slurry application timings on direct and indirect N2O emissions from free draining grassland.
In: Towards a better efficiency in N use (Bosch, A., Teira, M.R., Villar, J.M. [eds.]), Proceedings of the
15th Nitrogen Workshop, 297-299. Lleida (Spain).
Zaman, M., Saggar, S., Blennerhassett, J.D., Singh, J. (2009). Effect of urease and nitrification inhibitors on N
transformation, gaseous emissions of ammonia and nitrous oxide, pasture yield and N uptake in grazed
pasture system. Soil Biology and Biochemistry 41, 1270-1280.
6 Field application of organic and inorganic
fertilizers: working group document
Author: Tom Misselbrook
The following document builds upon the “Field application of organic and inorganic fertilizers:
background document (chapter 5)”, and provides a summary of discussions held during the workshop
by the working group for this theme.
6.1 Group composition
The working group for theme 3 comprised approximately 30 people with interests covering GHG
emissions, soil C, ammonia emissions, N leaching, water quality, catchment management, bio-
economy, fertilizers, recycling organic wastes, crop production, crop quality, soil quality, bio-based
fertilizers, agroecology, ecosystems approach and optimization of nutrient cycles. Countries
represented were Belgium, Canada, Czech Republic, Denmark, the EU Commission, France, Germany,
Italy, the Netherlands, Norway, Poland, Portugal, Spain, Ukraine and the United Kingdom.
6.2 Boundaries
It was agreed that the focus of the report should remain as N but should also include some consideration
of the implications of potential N mitigation measures on the cycling/loss pathways of other nutrients,
on soil C and other ecosystem services as appropriate.
In terms of regional boundaries, the primary focus is the EU although inclusion of the wider European
region is entirely appropriate. Categorisation of agro-climatic regions within this was considered as
useful (considering the key drivers of different processes, relative importance of N pathways and
regional differences in management practices). However, the report should not be overly constrained
by regional aspects and there is a danger of becoming too site-specific, but while the overall aim is to
improve N use efficiency and minimise losses to the environment, there will be areas where one form
of N loss is considered more important to control than another. Inclusion of references to specific
(existing) case-studies may be appropriate in this context.
6.3 Knowledge and data gaps
The usefulness of a join-up N Guidance Document will depend on the completeness and robustness of
the underlying data, models and assumptions. It is important therefore to identify current gaps and
uncertainties, the extent to which these may compromise guidance and what steps might be taken to
address this. The group identified several issues in this respect:
Baseline data regarding agricultural practices – the availability, detail and quality of data on
agricultural practices which will influence N uptake and loss pathways varies considerably
across different countries.
Data availability for modelling – even where data exist, they are often difficult to obtain for
modelling purposes and there will be inherently large (generally unquantified) uncertainties in
model outputs at regional scale.
Characterisation and management of crop residues – these are often poorly quantified but may
be important in determining the soil mineral N content at times of high vulnerability to e.g.
nitrate leaching.
Soil N balances – particularly over the longer term and may represent a significant source or
sink according to management which is currently overlooked.
Nitrogen returns to the atmosphere through total denitrification – this is often a large part of
the overall N budget but is the N2 component is associated with very large uncertainty; while
environmentally benign, more certainty around the fate of applied N either as a loss as N2
through denitrification or potentially as an increase in the soil N content could improve
subsequent guidance.
Table 1. Potentail impact of management practices on Nitrogen losses from agricultural soils.
Practice Leaching/runoff Ammonia volatilization Nitrous oxide Notes
Inorganic mineral
fertilizers
Appropriate rate and timing Timing (wet) that reduces
NH3 my increase leaching
or denitrification
Replace urea with AN ~ ~ Urea is cheaper and possibly
safer. OK for some
situations (injection)
Use urease inhibitor ~ ~ Can reduce synchrony
between crop demand and
availability of N. May
increase leaching of urea.
Use nitrification inhibitor ~ Can reduce synchrony
between crop demand and
availability of N
Use slow release fertilizers ~ ~ ~
Livestock manures
Integrated N management
plan
Apply slurries by band
spreading/trailing shoe
~ ~
Apply slurries by injection ~ ~ Shallow injection can create
runoff channels
Slurry dilution for fertigation ~ ~
Slurry acidification ~ ~
Use nitrification inhibitors ~
Rapid incorporation of
manures after application
~ ~
Anaerobic digestion ~ ~ ~ Depends on management of
facility and subsequent
digestate
Livestock grazing
Shorter grazing season Needs to be assessed across
the full system
Use nitrification inhibitors ~
Tillage and cropping
Use cover crops ~
Use minimum tillage
practices
~ ~
Use legumes Potential for higher winter
losses due to mineralization
and freeze thaw
Crop residue management? ~ ~
Choice of low protein
varieties
These have low N demands,
but must be reconciled with
end-users & markets.
6.4 Next steps
Further plenary discussion among all proposed chapters for the Guidance Document to agree
focus, structure and content
Draft ‘Land application’ chapter (BG3 document authors) for circulation to wider WG3
participants
Present ‘Land application’ chapter to next Brussels meeting for agreement/discussion/revision
7 Land use and landscape management:
background documents
Author: Tommy Dalgaard
The following chapter provides an overview of land use and landscape management practices that can
contribute to better nitrogen management in agiculture systems, and was used as a background
document by the “land use and landscape management working group”.
7.1.1 Introduction
The present document aims to review how different types of land use and landscape management
practices can contribute to a more sustainable use of nitrogen (N) for production while mitigating the
negative effects of reactive nitrogen (Nr) in the environment, and thereby summarize which elements
to include in future joined-up nitrogen guidance for air, water and climate co-benefits.
The work is related to the UN Task Force on Reactive Nitrogen (UNECE-TFRN, http://www.clrtap-
tfrn.org/). In line with previous guidance documents on Options for Ammonia Mitigation (Bittman et
al. 2014), it synthesizes knowledge from national and international studies within the area, based on
expert knowledge.
7.1.2 Why consider landscape level management?
There are at least, two important reasons to consider land use changes and landscape level management
practices for a better use of nitrogen, and the mitigation of unwanted air, water or climate related Nr
effects:
1. The problems with Nr can be addressed exactly where they appear; both in space and time. For
example hot spots of ammonia emissions from livestock houses and slurry tanks can be mitigated
by planting trees around the source area, specifically in the major wind directions; or vegetation
can be established specifically around protected nature areas, or in buffer zones around protected
streams, to effectively catch Nr right before it reaches the vulnerable environment. Another example
could be the strategic establishment of smaller or larger wetlands to clean/treat polluted water from
field drains or dikes via denitrification and sedimentation before it reaches vulnerable surface
waters, or spatio-temporal timing of grassland management and manure distribution for
minimization of N-losses in vulnerable areas or times of the year (For example in dedicated
groundwater protection areas).
2. The measures can be cheaper compared to the other types of measures3, because they can be placed
outside valuable production areas, without limiting the production, and thereby potentially at lower
costs. In this way additional nature and recreational values from the new landscape elements in the
form of hedgerows, forests, extensive buffer-zones around streams, and wetlands could be created.
Thereby, it can be stated that strategic land use changes and landscape level management practices have
benefits via a combination of environmental (point 1) and economic (point 2) effects, corresponding to
the biophysical and socioeconomic factors.
As a recent example, both the environmental and the economic factors have been put forward as an
argument for the paradigm shift towards a more landscape level measures in the Danish nitrogen
regulation, with more geographically differentiated and targeted measures to be implemented over the
coming years (Dalgaard et al. 2013, 2016). The environmental argument is that the requirements of the
EU Water Framework- and The National Emissions Ceiling Directives can only be met by new
geographically targeted, landscape scale measures on top of the exiting general measures, and therefore
they are urgently needed. The economic argument is that a shift towards more landscape scale measures
will be a cheaper solution, because of the arguments under point 2 above, and because the
implementation extent of the general measures have been so large that they go considerably over both
the farm- and the welfare economic optimum (for instance the N fertilisation of crops have until now
been restricted to 15-18% below the production economic optimum).
One of the major challenges for the shift towards more geographically targeted, landscape level N
measures is the knowledge about- and documentation of their effects. This was also the conclusion from
the landscape component of the Nitro-Europe project (http://www.nitroeurope.eu/), where pilot
research studies were carried out in 6 European case landscapes (see for example Dalgaard et al. 2012),
and the corresponding chapter of the European Nitrogen Assessment (Cellier et al. 2011) experiences
from key national research projects was included, covering studies from The Netherlands, Scotland,
France, Denmark and others. Based on these studies, Cellier et al. (2011) synthesized that “At field or
farmstead scales, processes of N transformation and transfer have been extensively studied, and have
given a fair insight into the fate of N at small space and time scales. When going beyond the field or
farmstead boundaries (i.e. the landscape, watershed, regional scales), N can be transferred in significant
amounts from Nr sources (e.g. farmsteads, field after slurry/fertilizer application, etc.) to the recipient
ecosystems by a variety of pathways. For example, atmospheric NH3 emitted from animal housing or a
field can be re-deposited to the foliage of nearby ecosystems in amounts that increase the closer the
source is horizontally to the recipient ecosystem and vertically to the soil surface (Fowler et al. 1998;
Loubet et al. 2006). Similarly, wetlands or crops/grasslands at the bottom of slopes can recapture NO3−
in the groundwater that originates from N applied further up the slope. In both cases, this can lead to
large inputs of N to the receptor ecosystem that may have potential impacts on the ecosystem (Pitcairn
et al. 2003) and the biogeochemical cycles, possibly leading to enhanced N2O and NO emission
(Beaujouan et al. 2001; Skiba et al. 2006; Pilegard et al, 2006) and further feeding the N cascade
(Galloway et al. 2003) (see below, Figure 1). These N2O emissions resulting from N transfer in receptor
ecosystem are usually called indirect emissions and may represent a significant fraction of total N2O
emissions, although how much remains uncertain (Mosier et al. 1998). The importance of uncultivated
or marginal areas that are outside or peripheral to the agricultural systems for flows and budgets of
energy and matter, including N, emphasizes the need to adopt a landscape perspective”.
3 Described in the theme reports of Amon (2016) and Misselbrook et al. (2016)
7.1.3 Nitrogen flows in the rural landscape
Figure 17 gives an overview of the reactive N flows in rural landscapes, and show the cascade of
reactions from Nr input in the form of fertilisers and feed, through the cropping and livestock system,
and to the natural ecosystems. It is especially the Nr flows to and from the natural/semi-natural
ecosystems that are targeted by the landscape level measures exemplified above. These flows can be
divided in those relating to air pollution, including the related greenhouse gas (GHG) emissions (Figure
18), those related to surface- and groundwater pollution (Figure 19), and those related to sources and
sinks of nitrogen.
Figure 17. Simplified overview of nitrogen flows highlighting major anthropogenic sources, the cascade of reactive
nitrogen forms (adapted from Sutton et al. 2013)
7.1.4 Air pollution and related greenhouse gas emissions
Figure 18. Nitrogen flows in rural landscape (Adapted after Kros et al. 2007, cf. Cellier et al. 2011).
7.1.5 Surface and groundwater pollution
Figure 19. Conceptual model of the shallow groundwater bodies and their interaction with dependent aquatic
ecosystems in the Odense Pilot River Basin, Denmark. The N and P transport pathways to the aquatic ecosystems are
indicated (Hilsby et al 2008)
7.1.6 Scale issues
Nitrogen flow and transformations are determined by the fine scale topography and spatial variability
of the biogeochemical and physical characteristics of the soil. These together with climate and
agricultural N management determine, in particular the nitrification and denitrification processes, which
determine the fluxes of NO, N2O, N2 to the atmosphere and the leaching of dissolved organic N and
NO3 to the rivers and other aqueous bodies.
In order to model N flow through the landscape it is important to have field scale/farm scale ‘activity’
data, such as agronomic management, N application rates, soil types and topography etc. New
technologies, e.g. drones, satellites, aircrafts, are valuable tools to provide these data (e.g. soil moisture,
topography, vegetation types). An example is the use of satellite vegetation maps to estimate landscape
scale CH4 fluxes (Dinsmore et al, 2016).
7.2 Summary and conclusions
The following table is provided for discussion and outlines how different landscape management
strategies can impact nitrogen losses (Table 17).
Table 17. Landscape management impact on nitrogen losses
Practice Leaching
/runoff
Ammonia
volatilization
Nitrous oxide
emissions Notes
Riparian buffer
strips
N2O mitigation rate depends on the
soil matter content and soil wetness
Agroforestry Chickens or pigs in woodlands
Planting trees on
steep slopes
Taking these areas out of agriculture
will reduce N translocation and
accumulation in the valleys, and
reduce erosion, dust
Shelterbelts around
large NH3 point
sources
Concentrates N deposition to the
shelterbelts, so less NH3 deposition
onto other, perhaps fragile land, but
increased NO, N2O emissions and
NO3 leaching from these shelterbelts
Biodiversity buffer
strips around fields ?
Can improve crop yield, thereby
NUE and less N losses
Reduction of Pathogen transfer
Hedgerows
May intercept some of the NH3 from
the field, when on slopes can reduce
NO, N2O & NO3
Increased biomass = C
sequestration,
Mixed farm model
and crop rotation
Include outdoor pigs/chickens in
crop rotation, and reduce fertiliser N
input rates at landscape scale
In the European Nitrogen Assessment, Cellier et al. (2011) summarized the following key points in
relation to nitrogen flows and fate in rural landscapes.
Nature of the problem:
The transfer of nitrogen by either farm management activities or natural processes (through the
atmosphere and the hydrological network) can feed into the N cascade and lead to indirect and
unexpected reactive nitrogen emissions.
This transfer can lead to large N deposition rates and impacts to sensitive ecosystems. It can
also promote further N2O emission in areas where conditions are more favourable for
denitrification.
In rural landscapes, the relevant scale is the scale where N is managed by farm activities and
where environmental measures are applied.
Approaches:
Mitigating nitrogen at landscape scale requires consideration of the interactions between natural
and anthropogenic (i.e. farm management) processes.
Owing to the complex nature and spatial extent of rural landscapes, experimental assessment
of reactive N flows at this scale are difficult and often incomplete. It should include
measurement of N flows in the different compartments of the environment and a comprehensive
datasets on the environment (soils, hydrology, land use, etc.) and on farm management.
Modelling is the preferred tool to investigate the complex relationships between anthropogenic
and natural processes at landscape scale although verification by measurements is required. Up
to now, no model includes all the components of landscape scale N flows: farm functioning,
short range atmospheric transfer, hydrology and ecosystem modelling.
Key findings/state of knowledge:
The way N is managed as well as the location of farming activities can have a strong influence
on N flows at landscape scale. Consequently, environmental measures can be more or less
effective according to the landscape and farming system, and the interactions between them.
The magnitude of nitrate transfers and subsequent impacts is linked to the hydrology of the area
(e.g. subsurface versus deep hydrological flows).
The magnitude of N losses to the atmosphere depends on the agronomic management, soil
properties and climate. There is a need to design mitigation options for local conditions.
Source-sink relationships for atmospheric transfer are linked to land use (e.g. patchiness,
hedgerows) and distance between sources and sensitive areas.
A verified integrated landscape model would be useful for investigating the N flows in rural
landscapes, as well as evaluating different N management strategies and environmental
measures at the landscape scale.
Major uncertainties/challenges:
The multiple pathways of N transfer, the interactions between natural and anthropogenic
processes and the risk of pollution swapping requires complex high resolution modelling.
Linkage of the different model components and the verification and uncertainty assessment of
the integrated model are big challenges.
A network of European landscapes, including different climatic conditions, hydrology and
farming systems, should be established as case studies to assess the influence of landscape
processes on N budgets.
Relevant data to verify the models.
Recommendations:
When designing and implementing new environmental measures, the landscape scale should
be considered in order to take into account processes (such as N deposition to sensitive areas
or indirect N2O emissions) that may mitigate the efficiency of the measures.
The implementation of environmental measures should consider the variety of landscape types
and allow adaptation to local conditions since their effectiveness might vary according to
landscape features and farming systems.
Environmental measures applied to different landscapes and farming systems should be
established and evaluated by modelling and verified, if possible, by monitoring once the
measures are in place.
7.3 References
Amon B (2016) Housed Livestock, manure storage and manure processing. Background document for the Joint
DG ENV & TFRN workshop: Towards joined-up nitrogen guidance for air, water and climate co-
benefits. Brussels, October 11th and 12th, 2016.
Beaujouan V., Durand P. and Ruiz L. (2001) Modelling the effect of the spatial distribution of agricultural
practices on nitrogen fluxes in rural catchments. Ecological Modelling 137, 93-105.
Bittman S, Dedina M, Howard CM, Oenema O and Sutton M (eds.) Options for Ammonia Mitigation. Guidance
from the UNECE Task Force on Reactive Nitrogen. Centre for Ecology and Hydrology, The UK. ISBN
978-1-906698-46-1.
Cellier P, Durand P, Hutchings N, Dragosits U, Theobald M, Drouet JL, Oenema O, Bleeker A, Breuer L,
Dalgaard T, Duretz S, Kros H, Loubet B, Olesen JE, Mérot P, Viaud V, de Vries W and Sutton MA
(2011) Nitrogen flows and fate in rural landscapes. In: Sutton MA, Howard CM, Erisman JW, Billen G,
Bleeker A, Grennfelt P, Grinsven H and Grizzetti B (eds.) The European Nitrogen Assessment. Chapter
11. P. 229-248 Cambridge University Press. ISBN 978-1-10700-612-6.
Dalgaard T, Brock S, Børgesen CD, Graversgaard M, Hansen B, Hasler B, Hertel O, Hutchings NJ, Jacobsen B,
Stoumann Jensen L, Kjeldsen C, Olesen JE, Schjørring JK, Sigsgaard T, Andersen PS, Termansen M,
Vejre H, Odgaard MV, de Vries W, and Wiborg I (2016) Solution scenarios and the effect of top down
versus bottom up N mitigation measures – Experiences from the Danish Nitrogen Assessment. Feature
Presentation for the International Nitrogen Initiative Conference INI2016. Melbourne, Australia.
http://www.ini2016.com/1236.
Dinsmore,K.J., Drewer,J., Levy,P.E., George,C., Lohila,A., Aurela,M. & Skiba,U.M. 2016 Growing season CH4
and N2O fluxes from a sub-arctic landscape in northern Finland. Biogeosciences Discussion10.5194/bg-
2016-238, 2016
Fowler D, Pitcairn CER, Sutton MA, Fléchard C, Loubet B, Coyle M, and Munro RC (1998) The mass budget
of atmospheric ammonia in woodland within 1 km of livestock buildings. Environmental Pollution, 102,
343-348.
Hinsby K, Condesso de Melob MT and Dahl M (2008) European case studies supporting the derivation of
natural background levels and groundwater threshold values for the protection of dependent ecosystems
and human health. Science of the Total Environment. Vol. 401, Issues 1–3, 15 August 2008, p. 1–20.
Misselbrook et al. (2016) Field application of organic and inorganic fertilizers. Background document for the
Joint DG ENV & TFRN workshop: Towards joined-up nitrogen guidance for air, water and climate co-
benefits. Brussels, October 11th and 12th, 2016.
Mosier A., Kroeze C., Nevison C., Oenema O., Seitzinger S. and van Cleemput O (1998) Closing the global
N2O budget: nitrous oxide emissions through the agricultural nitrogen cycle. Nutrient Cycling in
Agroecosystems, 52 (2-3), 225-248.
Pilegaard,K., Skiba,U., Ambus,P., Beier,C., Brueggemann,N., Butterbach-Bahl,K., Dick,J., Dorsey,J.,
Duyzer,J., Gallagher,M., Gasche,R., Horvath,L., Kitzler,B., Leip,A., Pihlatie,M., Rosenkranz,P.,
Seufert,G., Vesala,T., Westrate,H. & Zechmeister-Boltenstern,S. 2006. Factors controlling regional
differences in forest soil emission of nitrogen oxides (NO and N2O). Biogeosciences, 3, 651-661.
Pitcairn C E R, Fowler, D., Leith I. D., Sheppard L. J., Sutton M. A., Kennedy V, Okello E. (2003)
Bioindicators of enhanced nitrogen deposition. Environmental Pollution, 126 (3): 353-361.
Skiba,U., Dick,J., Storeton-West,R., Lopez-Fernandez,S., Woods,C., Tang,S. & van Dijk,N. 2006. The
relationship between NH3 emissions from a poultry farm and soil NO and N2O fluxes from a downwind
forest. Biogeosciences, 3, 375-382.
Sutton MA, Howard CM, Erisman JW, Billen G, Bleeker A, Grennfelt P, Grinsven H and Grizzetti B (2011,
eds.) The European Nitrogen Assessment. Cambridge University Press. ISBN 978-1-10700-612-6. 612 p.
8 Land use and landscape management:
working group report
Author: Tommy Dalgaard
The following document builds upon the “Land use and landscape management: background
document (chapter 7)”, and provides a summary of discussions held during the workshop by the
working group for this theme.
The present document summarizes the workshop results and conclusions and aims to review how
different types of land use and landscape management practices can contribute to a more sustainable
use of nitrogen (N) for production while mitigating the negative effects of reactive nitrogen (Nr) in the
environment, and thereby summarize which elements to include in future joined-up nitrogen guidance
for air, water and climate co-benefits.
The work is related to the UN Task Force on Reactive Nitrogen (UNECE-TFRN, http://www.clrtap-
tfrn.org/) and synthesizes expert knowledge from national and international studies within the area.
8.1 Summary and conclusions
Based on the European Nitrogen Assessment, and for further development, the following key points in
relation to nitrogen flows and fate in rural landscapes are summarized (Cellier et al. 2011): ”
8.2 Nature of the problem
The transfer of nitrogen by either farm management activities or natural processes (through the
atmosphere and the hydrological network) can feed into the N cascade and lead to indirect and
unexpected reactive nitrogen emissions.
This transfer can lead to large N deposition rates and impacts to sensitive ecosystems. It can
also promote further N2O emission in areas where conditions are more favourable for
denitrification.
In rural landscapes, the relevant scale is the scale where N is managed by farm activities and
where environmental measures are applied.
8.3 Approaches
Mitigating nitrogen at landscape scale requires consideration of the interactions between natural
and anthropogenic (i.e. farm management) processes.
Owing to the complex nature and spatial extent of rural landscapes, experimental assessment
of reactive N flows at this scale are difficult and often incomplete. It should include
measurement of N flows in the different compartments of the environment and a comprehensive
datasets on the environment (soils, hydrology, land use, etc.) and on farm management.
Modelling is the preferred tool to investigate the complex relationships between anthropogenic
and natural processes at landscape scale although verification by measurements is required. Up
to now, no model includes all the components of landscape scale N flows: farm functioning,
short range atmospheric transfer, hydrology and ecosystem modelling.
8.4 Key findings/state of knowledge
The way N is managed as well as the location of farming activities can have a strong influence
on N flows at landscape scale. Consequently, environmental measures can be more or less
effective according to the landscape and farming system, and the interactions between them.
The magnitude of nitrate transfers and subsequent impacts is linked to the hydrology of the area
(e.g. subsurface versus deep hydrological flows)
The magnitude of N losses to the atmosphere depends on the agronomic management, soil
properties and climate. There is a need to design mitigation options for local conditions.
Source-sink relationships for atmospheric transfer are linked to land use (e.g. patchiness,
hedgerows) and distance between sources and sensitive areas
A verified integrated landscape model would be useful for investigating the N flows in rural
landscapes, as well as evaluating different N management strategies and environmental
measures at the landscape scale.
8.5 Major uncertainties/challenges
The multiple pathways of N transfer, the interactions between natural and anthropogenic
processes and the risk of pollution swapping requires complex high resolution modelling.
Linkage of the different model components and the verification and uncertainty assessment of
the integrated model are big challenges.
A network of European landscapes, including different climatic conditions, hydrology and
farming systems, should be established as case studies to assess the influence of landscape
processes on N budgets.
Relevant data to verify the models
8.6 Recommendations
When designing and implementing new environmental measures, the landscape scale should
be considered in order to take into account processes (such as N deposition to sensitive areas
or indirect N2O emissions) that may mitigate the efficiency of the measures
The implementation of environmental measures should consider the variety of landscape types
and allow adaptation to local conditions since their effectiveness might vary according to
landscape features and farming systems.
Environmental measures applied to different landscapes and farming systems should be
established and evaluated by modelling and verified, if possible, by monitoring once the
measures are in place.”
9 Plans for a future joined up guidance
document
9.1 Key questions regarding a guidance document
The working groups discussed a number of important questions relating to a suggested “EC / UNECE
Guidance Document on Joined-up Nitrogen Management in Agriculture“. The following texts
summarises some of the key questions raised and the repsonse provided.
Why write this guidance document?”
• Awareness raising beyond the traditional departments;
• N is central to many current policy issues, including the SDGs, COP-Paris; sense of urgency
• Shared common approach
• Energizing policy makers
• The promises of overall nitrogen management
– Greater effectiveness of (policy) measures
– Less implementation & transaction costs
– More synergy, less negative side effects
– More social support
• Guidance/recommendations
– Illustration of successful cases
Who is the audience for this document?
• Policy makers,
– Central agencies (Agric, Env., Finance, Health, Trade)
– Leaders in food industry and agriculture,
– Scientists
– Extension services
• UN-ECE region, including north America, EECCA - region, European Union
What would a guidance document look like?
• Effective communication is extremely important
• Compelling story, with convincing graphics
– “highlighting the severity of issues”
– “highlighting lots of opportunities to improve the situation”
• Start broad, focus on agriculture (funneling)
• Key messages on one page
• Maximal 20 pages
• Extended version for die-hards
• Summary of key messages in video/online
What should be included in a guidance document?
impacts of all important N loss pathways should be included (NH3, N2O, total denitrification,
leaching); quantification as far as possible, indication of direction of change where less
certainty
impact on crop yield
notes on important impacts to other pollutants
notes on key drivers regarding effect (and therefore potential regional differences in impact)
an indication of costs
extent to which the practice might be realised
barriers to implementation
level of confidence regarding the estimates of impacts
notes on ease of monitoring/verifying uptake
What are the top multi-beneficial measures that should be included?
Discussion as to which practices and specific mitigation methods should be included in the Guidance
document was not exhaustive and an iterative process would be required to fully populate such a list.
However, working groups did discuss the difficulties of defining a baseline practice (from which to
measure impacts of change), which may vary considerable across the European region and would
therefore have to be clearly defined in any guidance document. Additionally, the importance of
explaining the drivers for key loss processes and therefore the need to target the guidance or ensure
appropriate interpretation where specific regional differences occur was stressed. There was also some
discussion regarding generic vs specific measures (e.g. ‘a farm-specific nutrient management plan’ vs
‘use of a urease inhibitor with urea fertilizer applications’) and how these might best be dealt with and
presented.
Key measures that we suggested included:
1. Introducing targets for NUE, Nsurplus and Noutput
2. Spatial and temporal scales important
3. Targets for protein intake for animals and humans
4. Law of the optimum (law of Liebscher)
5. 5 R principles
6. Reduce food waste and losses
7. Utilize animal excrements, residues, and household wastes effectively
8. Improve education and research
9. Need for technology development
10. Develop novel financial instruments/incentives
What are the next steps in developing such a guidance document?
Further plenary discussion among all proposed chapters for the Guidance Document to agree
focus, structure and content
Revision of the timeline
Start drafting
10 DG-ENV Guidance Document – A skeleton
plan for a future “EC/UNECE Guidance
Document on Joined-up Nitrogen
Management in Agriculture”.
10.1 Feedback on document structure
How to best summarize the wealth of information that should be included in a a future “EC / UNECE
Guidance Document on Joined-up Nitrogen Management in Agriculture, in a readable, readily-
understandable way is still for further discussion. The document would need to include consideration
of how other chapters are structured, potential overlap and/or linking of messages across chapters and
the amount of detail presented versus referenced material.
A simplified structure of a suggested report below, was suggested by working group one:
• Abstract/summary (1 page)
• Introduction (why, why now) (1 page)
• Context (issues, scales, economics) (5 pages)
o N in society and the environment
o N in food systems
o N in agriculture
o N targets
• Principles of overall nitrogen management (5 pages)
• Tools for overall nitrogen management (2 pages)
• Communication/stakeholders (2 pages)
• Recommendations/consequences for policy (1 page)
• Annexes, underlying reports
Whilst working group 3, suggested that structuring could be ordered by N inputs to land (mineral
fertilizers, livestock manure, other organic amendments, crop residues, grazing returns, biological N
fixation), with specific measures/practices, or groups of measures applicable to each (there would be
some overlap).
Each working group leader was asked to provide a list of suggested headings for a chapter based on
their theme and the feedback they had received from working group discussions. Their response provide
the ‘more‘ detailed ‘skeleton structure’ below.
105
10.2 Suggested skeleton structure of a joined up guidance document
Executive Summary
Chapter 1: Principles of overall N management
Based on suggestions by Oene Oenema
1.1 Nitrogen management
1.2 Dimensions of integration
Vertical integration
Horizontal organization
Integration of other elements and compounds
Stakeholder involvement and integration
Regional integration
1.3 Tools for integrated approaches to N management
Nitrogen balances
Integrated assessment modeling
Logistics and chain management
Stakeholder dialogue
1.4 Elements of integrated nitrogen management
Integrated management pracitices
Farm Nitrogen Budgets
1.5 Measures to prevent and nitrogen losses
Livestock feeding strategies
Animal Housing
Manure Storage
Manure application techniques
Fertilizer application techniques
1.6 Existing nitrogen policies
1.7 The Nitrates Directive
Recommendations for measures under the Nitrates Directive
Example recommendations for measures
1.8 Chapter Conclusions, final remarks and research questions
Chapter 2: Housed livestock, manure storage and manure processing
Based on suggestions by Barbara Amon
2.1 Overview of nitrogen management in livestock production
2.2 Livestock Housing
Pig housing
Poultry housing
Housing systems for laying hens
106
Housing systems for broilers
2.3 Livestock feeding
Feeding strategies for dairy and beef cattle
Feeding strategies for pigs
Feeding strategies for poultry
Cattle housing
2.4 Manure Storage and Processing
2.5 Mitigation options
2.6 Chapter Conclusions, final remarks and research questions
Chapter 3: Field application of organic and inorganic fertilizers
Based on suggestions by Tom Misselbrook
3.1 Nitrogen applied to land
3.2 Potential nitrogen loss pathways
Regional considerations
Spatial considerations
3.4 Guidance on measures, practices and monitoring – (grouped according to nitrogen input category);
Nitrogen loss pathways
Yield effect
Other pollutants
Key influencing drivers
Costs
Scope for implementation
Barriers
Confidence in current knowledge
Ease of monitoring/verification
3.5 Chapter Conclusions, final remarks and research questions
Chapter 4: Land use and landscape management
Based on suggestions by Tommy Dalgaard
4.1 Why consider landscape level management?
4.2 Background: Nitrogen flows in the rural landscape
Air pollution and related greenhouse gas emissions
Surface- and groundwater pollution
Nitrogen sinks and sources
4.3 Guidance catalogue of land use and landscape management practices
4.4 Geographically targeted land use change:
Set aside
Integrated Buffer Zones (Riparian Buffer Strips)
Biodiversity buffer strips around fields
107
Hedgerows and afforestation
Changed crop rotation/ perennial crops (for e.g. permanent grasslands)
Agroforestry
Wetlands and watercourse restoration
Constructed mini-wetlands
4.5 Geographically targeted management:
Soil tillage and conservation (for e.g. no till on organic soils)
Drainage and controlled drainage
Grassland management
Placement of livestock production
Manure (re)distribution
Fertigation
Placement of biogas plants and bio-refineries for biomass redistribution
4.6 Important factors for the overall assessment of Land Use and Landscape management measures
Heterogeneity effects
Biophysical factors
Socioeconomic factors
Scale issues
4.7 Chapter Conclusions, final remarks and research questions
References
Appendix
108
11 Existing guidance A range of existing guidance documents/sources regarding N use, losses and mitigation in the context
of managed agricultural land include:
Options for Ammonia Abatement: Guidance from the UNECE Task Force on Reactive
Nitrogen (http://www.clrtap-tfrn.org/content/options-ammonia-abatement-guidance-unece-
task-force-reactive-nitrogen)
HELCOM Baltic Sea Action Plan (http://helcom.fi/baltic-sea-action-plan) See p86-96 for
agricultural measures
EU Project report: ‘Resource efficiency in Practice – Closing Mineral Cycles’
(http://ec.europa.eu/environment/water/water-
nitrates/pdf/Closing_mineral_cycles_final%20report.pdf) See p87 onwards. Also see project
outputs - Region-specific leaflets on best-practices
(http://ec.europa.eu/environment/water/water-nitrates/index_en.html)
Mainstreaming climate change into rural development policy post 2013. European
Commission 2014
(http://ecologic.eu/sites/files/publication/2015/mainstreaming_climatechange_rdps_post2013
_final.pdf) See Table 3 for list of measures
National fertilizer recommendations (e.g. UK RB209)
https://ahdb.org.uk/documents/RB209/RB209_Section1.pdf
National codes for good agricultural practice for EU countires
In addition to these, the working group identified the Best Available Technique Refence Document
(BREF) for intensive pig and poultry production under the Industrial Emissions Directive
(http://eippcb.jrc.ec.europa.eu/reference/). Regarding N, this has a focus on ammonia emissions and the
recently published (Feb 2017) BAT Conclusions document provides a list of those measures agreed to
give worthwhile reductions and generally applicable. However, little information is given regarding
impacts/interactions with other N pathways.