Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

CHAPTER 11

N2O EMISSIONS FROM MANAGED
SOILS, AND CO2 EMISSIONS FROMLIME AND UREA APPLICATION

2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories

11.1

Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Authors
Kristell Hergoualc’h (France), Hiroko Akiyama (Japan), Martial Bernoux (FAO), Ngonidzashe Chirinda (CGIAR,
Zimbabwe), Agustin del Prado (Spain), Åsa Kasimir (Sweden), James Douglas MacDonald (Canada), Stephen
Michael Ogle (USA), Kristiina Regina (Finland), Tony John van der Weerden (New Zealand)

Contributing Authors
Chang Liang (Canada), Alasdair Noble (New Zealand)

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Contents
11.

N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application
11.1

Introduction ....................................................................................................................................... 11.5

11.2

Nitrous oxide (N2O) Emissions from Managed Soils ....................................................................... 11.5

11.2.1

Direct N2O emissions ............................................................................................................. 11.5

11.2.1.1

Choice of method........................................................................................................ 11.6

11.2.1.2

Choice of emission factors.........................................................................................11.11

11.2.1.3

Choice of activity data ...............................................................................................11.14

11.2.1.4

Uncertainty assessment..............................................................................................11.21

11.2.2

Indirect N2O emissions .........................................................................................................11.21

11.2.2.1

Choice of method.......................................................................................................11.22

11.2.2.2

Choice of emission, volatilisation and leaching factors .............................................11.25

11.2.2.3

Choice of activity data ...............................................................................................11.27

11.2.2.4

Uncertainty assessment..............................................................................................11.27

11.2.3Completeness, Time series, QA/QC .....................................................................................11.27

11.3

CO2 Emissions from Liming ............................................................................................................11.27

11.4

CO2 Emissions from Urea Fertilization............................................................................................11.27

Annex 11A.2

Estimation of Default Emission Factor(s) for EF1 .....................................................11.29

Annex 11A.3

Estimation of Default Emission Factor(s) for EF1FR ..................................................11.32

Annex 11A.4

Estimation of Default Emission Factor(s) for EF3PRP ................................................11.33

Annex 11A.5

Estimation of Default Emission Factor(s) for EF4 .....................................................11.35

Annex 11A.6

Estimation of Default Emission Factor(s) for EF5 .....................................................11.36

Annex 11A.7

Estimation of Default Factor(s) for FracGASF .............................................................11.37

Annex 11A.8

Estimation of Default Factor for FracGASM ................................................................11.39

Annex 11A.9

Estimation of Default Factor for FracLEACH-(H) ...........................................................11.40

References..............................................................................................................................11.11.41

Equations
Equation 11.1

Direct N2O emissions from managed soils (Tier 1) .................................................... 11.6

Equation 11.2

Direct N2O emissions from managed soils (Tier 2) .................................................... 11.8

Equation 11.3

N from organic N additions applied to soils (Tier 1) .................................................11.14

Equation 11.4

N from animal manure applied to soils (Tier 1) ........................................................11.15

Equation 11.5

N in urine and dung deposited by grazing animals on pasture, range and paddock (Tier 1)...................................................................................................................................11.15

Equation 11.6 (Updated) N from crop residues and forage/pasture renewal (Tier 1) .....................................11.16
Equation 11.7

Dry-weight correction of reported crop yields...........................................................11.17

Equation 11.8

N mineralised in mineral soils as a result of loss of soil C through change in land use or
management (Tiers 1 and 2) ......................................................................................11.20

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Equation 11.9

N2O from atmospheric deposition of N volatilised from managed soils (Tier 1) ......11.22

Equation 11.10

N2O from N leaching/runoff from managed soils in regions where leaching/runoff occurs(Tier 1) .......................................................................................................................11.23

Equation 11.11

N2O from atmospheric deposition of N volatilised from managed soils (Tier 2) ......11.24

FigureFigure 11.1

Schematic diagram illustrating the sources and pathways of N that result in direct andindirect N2O emissions from soils and waters ............................................................ 11.9

Figure 11.2

Decision tree for direct N2O emissions from managed soils .....................................11.10

Figure 11.3

Decision tree for indirect N2O emissions from managed soils ..................................11.23

TablesTable 11.1 (Updated)

Default emission factors to estimate direct N2O emissions from managed soils .......11.13

Table 11.1a (New)

Default values for N AG(T), N BG(T), R AG(T), RS (T) and DRY to be used in Equations 11.6 and11.7 ............................................................................................................................11.18

Table 11.2 (Updated)

Alternative method and data for estimating above-ground residue (AGDM(T)) ...........11.19

Table 11.3 (Updated)

Default emission, volatilisation and leaching factors for indirect soil N2O emissions...................................................................................................................................11.26

Table 2A.1

Sample size, mean, and uncertainty range of the EF1 disaggregated by length of theexperiment (days) and n application rate (kg N ha-1 period-1) ...................................11.30

Table 2A.2

Sample size, mean, and uncertainty range of the EF1 disaggregated by climate, fertiliser
form and irrigation practice .......................................................................................11.31

Table 4A.1

EF values for cattle and sheep dung and urine, in wet and dry climates...................................................................................................................................11.34

Table 5A.1

Results from review papers on N addition experiments at non-agricultural sites ......11.35

Table 5A.2

Results from review papers on N2O emissions and N deposition at non-agricultural sites...................................................................................................................................11.35

Table 7A.1

Fertiliser consumption in the period 2007-2015 expressed as thousand tonnes nutrientsand % of total fertiliser consumed .............................................................................11.37

Table 7A.2

Assumptions on the potential mix of different IFA fertiliser products ......................11.37

Table 7A.3

Emission factors for % NH3–N and NOx-N (N applied)–1 from different fertiliser types
resulting from two meta-analysis and number of studies involved............................11.38

Table 8A.1

Emission factors for NH3–N and NOx-N (N applied or deposited)–1 from manure
application and excreta patches .................................................................................11.39

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

11.

N 2 O EMISSIONS FROM MANAGED SOILS,AND CO 2 EMISSIONS FROM LIME AND
UREA APPLICATION

Users are expected to go to Mapping Tables in Annex 1 Volume 4 (AFOLU), before reading this chapter. This isrequired to correctly understand both the refinements made and how the elements in this chapter relate to thecorresponding chapter in the 2006 IPCC Guidelines.

11.1

INTRODUCTION

No refinement.

11.2

NITROUS OXIDEMANAGED SOILS(N 2 O)EMISSIONSFROMThis section presents the methods and equations for estimating total national anthropogenic emissions of N2O(direct and indirect) from managed soils. The generic equations presented here can also be used for estimating
N2O within specific land-use categories or by condition-specific variables (e.g., N additions to rice paddies) if thecountry can disaggregate the activity data to that level (i.e., N use activity within a specific land use).
Nitrous oxide is produced naturally in soils through the processes of nitrification and denitrification. Nitrificationis the aerobic microbial oxidation of ammonium to nitrate, and denitrification is the anaerobic microbial reductionof nitrate to nitrogen gas (N2). Nitrous oxide is a gaseous intermediate in the reaction sequence of denitrification
and a by-product of nitrification that leaks from microbial cells into the soil and ultimately into the atmosphere.
One of the main controlling factors in this reaction is the availability of inorganic N in the soil. This methodology,
therefore, estimates N2O emissions using human-induced net N additions to soils (e.g., synthetic or organic
fertilisers, deposited manure, crop residues, sewage sludge), or of mineralisation of N in soil organic matter
following drainage/management of organic soils, or cultivation/land-use change on mineral soils (e.g., Forest
Land/Grassland/Settlements converted to Cropland).
The emissions of N2O that result from anthropogenic N inputs or N mineralisation occur through both a direct
pathway (i.e., directly from the soils to which the N is added/released), and through two indirect pathways: (i)following volatilisation of ammonia (NH3) and nitrogen oxides (NOx) from managed soils and from fossil fuelcombustion and biomass burning, and the subsequent redeposition of these gases and their products NH4+ andNO3- to soils and waters; and (ii) after leaching and runoff of N, mainly as NO3-, from managed soils. The principal
pathways are illustrated in Figure 11.1.
Direct emissions of N2O from managed soils are estimated separately from indirect emissions, though using acommon set of activity data. The Tier 1 methodologies do not take into account different land cover, soil type,climatic conditions or management practices (other than specified below). Neither do they take account of any lagtime for direct emissions from crop residue N, and allocate these emissions to the year in which the residues are
returned to the soil. These factors are not considered for direct or (where appropriate, indirect) emissions because
limited data are available to provide appropriate emission factors. Countries that have data to show that default
factors are inappropriate for their country should utilise Tier 2 equations or Tier 3 approaches and include a full
explanation for the values used.

11.2.1 Direct N 2 O emissions
In most soils, an increase in available N enhances nitrification and denitrification rates which then increase theproduction of N2O. Increases in available N can occur through human-induced N additions or change of land-use
and/or management practices that mineralise soil organic N.
The following N sources are included in the methodology for estimating direct N2O emissions from managed soils:• synthetic N fertilisers (FSN);• organic N applied as fertiliser (e.g., animal manure, compost, sewage sludge, rendering waste, waste water
effluent) (FON);• urine and dung N deposited on pasture, range and paddock by grazing animals (FPRP);

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application• N in crop residues (above-ground and below-ground), including from N-fixing crops 1 and from forages during
pasture renewal 2 (FCR);• N mineralisation associated with loss of soil organic matter resulting from change of land use or managementof mineral soils (FSOM); and• Drainage/management of organic soils (i.e., Histosols) 3 (FOS).

11.2.1.1 C HOICE OF METHOD
The decision tree in Figure 11.2 provides guidance on which tier method to use.
Tie r 1
In its most basic form, direct N2O emissions from managed soils are estimated using Equation 11.1 as follows:
EQUATION 11.1
DIRECT N2O EMISSIONS FROM MANAGED SOILS (TIER 1)

N 2ODirect −N = N 2O −N N inputs +N 2O−N OS +N 2O−N PRP

Where:

[(FSN + FON + FCR + FSOM ) • EF1 ] + 
N 2O−N N inputs = [(FSN + FON + FCR + FSOM )FR • EF1FR ]

( FOS ,CG ,Temp • EF2CG ,Temp ) + ( FOS ,CG ,Trop • EF2CG ,Trop ) +N 2O−N OS = ( FOS , F ,Temp , NR • EF2 F ,Temp , NR ) + ( FOS , F ,Temp , NP • EF2 F ,Temp , NP ) + ( FOS , F ,Trop • EF2 F ,Trop )






N 2O−N=PRP
( FPRP ,CPP • EF3 PRP ,CPP ) + ( FPRP , SO • EF3 PRP , SO ) 
Where:
N 2 ODirect −N = annual direct N2O–N emissions produced from managed soils, kg N2O–N yr-1

N 2 O−N N inputs = annual direct N2O–N emissions from N inputs to managed soils, kg N2O–N yr-1
N 2 O−N OS= annual direct N2O–N emissions from managed organic soils, kg N2O–N yr-1

1Biological nitrogen fixation has been removed as a direct source of N2O because of the lack of evidence of significant
emissions arising from the fixation process itself (Rochette and Janzen, 2005). These authors concluded that the N2O
emissions induced by the growth of legume crops/forages may be estimated solely as a function of the above-ground andbelow-ground nitrogen inputs from crop/forage residue (the nitrogen residue from forages is only accounted for during
pasture renewal). Conversely, the release of N by mineralisation of soil organic matter as a result of change of land use or
management is now included as an additional source. These are significant adjustments to the methodology previously
described in the Revised 1996 IPCC Guidelines. Countries may consider a Tier 2 approach for disaggregating low-N
concentration crop residues from high-N concentration residues. Current knowledge shows no evidence for such adisaggregation at Tier 1 (Graham et al. 2017).

2

The nitrogen residue from perennial forage crops is only accounted for during periodic pasture renewal, i.e. not necessarily
on an annual basis as is the case with annual crops.

3

Soils are organic if they satisfy the requirements 1 and 2, or 1 and 3 below (FAO, 1998): 1. Thickness of 10 cm or more. A
horizon less than 20 cm thick must have 12 percent or more organic carbon when mixed to a depth of 20 cm; 2. If the soil isnever saturated with water for more than a few days, and contains more than 20 percent (by weight) organic carbon (about
35 percent organic matter); 3. If the soil is subject to water saturation episodes and has either: (i) at least 12 percent (byweight) organic carbon (about 20 percent organic matter) if it has no clay; or (ii) at least 18 percent (by weight) organiccarbon (about 30 percent organic matter) if it has 60 percent or more clay; or (iii) an intermediate, proportional amount oforganic carbon for intermediate amounts of clay (FAO, 1998).

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

N 2 O−N PRP= annual direct N2O–N emissions from urine and dung inputs to grazed soils, kg N2O–N yr1

FSN= annual amount of synthetic fertiliser N applied to soils, kg N yr-1

FON

= annual amount of animal manure, compost, sewage sludge and other organic N additions
applied to soils (Note: If including sewage sludge, cross-check with Waste Sector to ensure
there is no double counting of N2O emissions from the N in sewage sludge), kg N yr-1

FCR

= annual amount of N in crop residues (above-ground and below-ground), including N-fixing
crops, and from forage/pasture renewal, returned to soils, kg N yr-1

FSOM

= annual amount of N in mineral soils that is mineralised, in association with loss of soil C
from soil organic matter as a result of changes to land use or management, kg N yr-1

FOS

= annual area of managed/drained organic soils, ha (Note: the subscripts CG, F, Temp, Trop,
NR and NP refer to Cropland and Grassland, Forest Land, Temperate, Tropical, Nutrient
Rich, and Nutrient Poor, respectively)

FPRP= annual amount of urine and dung N deposited by grazing animals on pasture, range andpaddock, kg N yr-1 (Note: the subscripts CPP and SO refer to Cattle, Poultry and Pigs, andSheep and Other animals, respectively)

EF1= emission factor for N2O emissions from N inputs, kg N2O–N (kg N input)-1(Table 11.1)

EF1FR= is the emission factor for N2O emissions from N inputs to flooded rice, kg N2O–N (kg N
input)-1 (Table 11.1) 4

EF2= emission factor for N2O emissions from drained/managed organic soils, kg N2O–N ha-1 yr1; (See guidance in 2013 Supplement to the 2006 IPCC Guidelines for National Greenhouse
Gas Inventories: Wetlands (Wetlands Supplement), Chapter 2, Table 2.5 where further
disaggregation by climate and land use is available) (Note: the subscripts CG, F, Temp, Trop,
NR and NP refer to Cropland and Grassland, Forest Land, Temperate, Tropical, Nutrient
Rich, and Nutrient Poor, respectively)

EF3PRP= emission factor for N2O emissions from urine and dung N deposited on pasture, range andpaddock by grazing animals, kg N2O–N (kg N input)-1; (Table 11.1) (Note: the subscripts
CPP and SO refer to Cattle, Poultry and Pigs, and Sheep and Other animals, respectively)

Conversion of N2O–N emissions to N2O emissions for reporting purposes is performed by using the following
equation:
N2O = N2O–N * 44/28
Tie r 2
If more detailed emission factors and corresponding activity data are available to a country than are presented in
Equation 11.1, further disaggregation of the terms in the equation can be undertaken. For example, if emission
factors and activity data are available for the application of synthetic fertilisers and organic N (FSN and FON) under
different conditions i, Equation 11.1 would be expanded to become 5:

4

When the total annual quantity of N applied to flooded paddy rice is known, this N input may be multiplied by a lower default
emission factor applicable to this crop, EF1FR (Table 11.1) or, where a country-specific emission factor has been determined,by that factor instead.

5

It is important to note that Equation 11.2 is just one of many possible modifications to Equation 11.1 when using the Tier 2
method. The eventual form of Equation 11.2 will depend upon the availability of condition-specific emission factors and theability to which a country can disaggregate its activity data.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

EQUATION 11.2
DIRECT N2O EMISSIONS FROM MANAGED SOILS (TIER 2)

N 2ODirect −N=∑ ( F + F ) • EF + ( F + F ) • EF + N O−N
i

SN

ON

i

1i

CR

SOM

1

2

OS

+ N 2O−N PRP

Where:
EF1i= emission factors developed for N2O emissions from synthetic fertiliser and organic N
application under conditions i (kg N2O–N (kg N input)-1); i = 1, …nEquation 11.2 may be modified in a variety of ways to accommodate any combination of N source-, crop type-,
management-, land use-, climate-, soil- or other condition-specific emission factors that a country may be able toobtain for each of the individual N input variables (FSN, FON, FCR, FSOM, FOS, FPRP).

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Figure 11.1

Schematic diagram illustrating the sources and pathways of N that
result in direct and indirect N 2 O emissions from soils and waters

Note: Sources of N applied to, or deposited on, soils are represented with arrows on the left-hand side of thegraphic. Emission pathways are also shown with arrows including the various pathways of volatilisation of NH3
and NOx from agricultural and non-agricultural sources, deposition of these gases and their products NH4+ andNO3-, and consequent indirect emissions of N2O are also illustrated. “Applied Organic N Fertilisers” include
animal manure, all compost, sewage sludge, tankage, etc. “Crop Residues” include above- and below-groundresidues for all crops (non-N and N fixing) and from perennial forage crops and pastures following renewal. On
the lower right-hand side is a cut-away view of a representative sections of managed land; Histosol cultivation isrepresented here.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Figure 11.2

Decision tree for direct N 2 O emissions from managed soils
Start

For
each N source ask:
Do you have country-specificactivity data1?

No

Obtain countryspecific data

Is thisa key category2 and is thisN source significant3?

Yes

Yes

No

Estimate emissions using Tier 1 equations,default emission factors, FAO activity data
for mineral N fertiliser use and livestock
populations, and expert opinion on otheractivity data.

Do youhave rigorously
documented country-specificemission factors
for EF1, EF2, and/or
EF3PRP?

Yes

Box 1: Tier 1

No

Estimate emissions using Tier 2 equation
and available country-specific emission
factors, or Tier 3 methods.

Estimate emissions using the Tier 1
default emission factor value andcountry-specific activity data.

Box 3: Tier 2 or 3

Box 2: Tier 1

Note
1: N sources include: synthe tic N fe rtiliser, organic N additions, urine a nd dung deposited during grazing, crop/forage residue, minera lisa tionof N containe d in soil organic matte r that acc ompanies C loss from soils following a change in land use or m ana gem ent and drainage/
management of organic soils. Other organic N additions (e.g. compost, sewage sludge, rendering waste) can be included in this calc ulation if
suff icient informa tion is ava ilable. The waste input is m easure d in units of N and added as an additiona l source sub-term under FON in
Equation 11.1 to be m ultiplied by EF1.
2: Se e Volum e 1 C hapter 4, "Methodological Choice and Ide ntif ication of Ke y Ca tegories" (noting Section 4.1.2 on limite d resources), for
discussion of key categor ies and use of decision trees.
3: As a rule of thumb, a sub-category would be signif icant if it accounts for 25-30% of emissions from the source cate gory.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Compilers can develop Tier 2 emission factors specific to mitigation options such as the application of nitrification
inhibitors (Akiyama et al. 2010, Ruser & Schulz 2015, Gilsanz et al. 2016). Compilers can also consider an
exponential response of N2O emissions to N application by developing country-specific emission factors (vanGroenigen et al. 2010, Shcherbak et al. 2014, Gerber et al. 2016). This method will require activity data on specificfertiliser application rates to individual fields in order to apply rate-specific emission factors that capture theexponential response 6. The influence of other environmental conditions, such as freeze-thaw cycles (WagnerRiddle et al. 2017) can also be addressed with the development of Tier 2 emission factors.
Conversion of N2O–N emissions to N2O emissions for reporting purposes is performed by using the following
equation:
N2O = N2O–N * 44/28
Tie r 3Tier 3 methods are modelling or measurement approaches. Models are useful because in appropriate forms they
can relate the soil and environmental variables responsible for N2O emissions to the size of those emissions. These
relationships may then be used to predict emissions from whole countries or regions for which experimental
measurements are impracticable. Models should only be used after validation by representative experimental
measurements. Care should also be taken to ensure that the emission estimates developed through the use of models
or measurements account for all anthropogenic N2O emissions 7. Guidance that provides a sound scientific basis
for the development of a Tier 3 Model-based system is given in Chapter 2, Section 2.5.
According to Equation 11.1, direct emissions of N2O from managed soils are calculated in the Tier 1 approach on
the basis of total N applied to soils as synthetic and organic fertilisers and/or soil N mineralisation. The processesof run-off of N, volatilization of NH3 and NOx, emissions of N2O, and leaching of N, however, do not occur
simultaneously but in a sequence, with the peak of run-off and NH3+NOx volatilization happening before emissionsof N2O and losses of N through leaching. For example, an application technique affecting the volatilization rate of
NH3+NOx is likely to change the flow rates of subsequent processes. To illustrate, injecting slurry instead ofbroadcasting the organic amendment may increase the availability of N for N2O emissions and/or N-leaching,depending on climatic and soil conditions (Chadwick et al. 2011). It is therefore good practice to carefully assess
such ’pollution swapping’ effects when implementing a Tier 3 approach and adopting the N-flow principle whenestimating direct N2O emissions. The same applies when estimating indirect N2O emissions from leaching andrunoff (see Section 11.2.2.1). This adoption can be achieved by accounting for the decreased pool of nitrogen thatis available for direct N2O emissions (and nitrogen leaching).

11.2.1.2 C HOICE OF EMISSION FACTORS
Tie r s 1 a nd 2
Three emission factors (EF) are needed to estimate direct N2O emissions from managed soils. The default values
presented here may be used in the Tier 1 equation or in the Tier 2 equation in combination with country-specificemission factors. The first EF (EF1) refers to the amount of N2O emitted from the various synthetic and organic N
applications to soils, including crop residue and mineralisation of soil organic carbon in mineral soils due to landuse change or management. The second EF (EF2) refers to the amount of N2O emitted from an area ofdrained/managed organic soils, and the third EF (EF3PRP) estimates the amount of N2O emitted from urine anddung N deposited by grazing animals on pasture, range and paddock. Default emission factors for the Tier 1 method
are summarised in Table 11.1. For EF2, see guidance in 2013 Supplement to the 2006 IPCC Guidelines for National
Greenhouse Gas Inventories: Wetlands, Chapter 2, Table 2.5.
The default value for EF1 has been set at 1 percent of the N applied to soils or released through activities that resultin mineralisation of organic matter in mineral soils 8. Given the growing number of studies highlighting the role
6 The Tier 1 method is designed as a simple method for estimating direct N O emissions with top-down commodity data on
2

fertiliser production, import/export, or sales data. With these data, it is not possible to know the application rates to individual
fields, which is needed for emission factors that are adjusted with application rates. However, variable emission factors canbe developed with the Tier 2 method.

7

Natural N2O emissions on managed land are assumed to be equal to emissions on unmanaged land. These latter emissions
are very low. Therefore, nearly all emissions on managed land are considered anthropogenic. Estimates using the IPCC
methodology are of the same magnitude as total measured emissions from managed land. Some Tier 3 methods may estimate
only part of or aggregate some of the emission sources. Developers of Tier 3 methods should be aware of which componentsof Equation 11.2 are included in the estimate produced by their country-specific method.

8

The value of EF1 draws on a much larger number of measurements (see Annex 11A.2) than were available for the previous
value used for EF1 in the 2006 IPCC Guidelines (Bouwman et al. 2002a,b; Novoa & Tejeda 2006; Stehfest & Bouwman2006).

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11.11

Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Applicationof climate and fertiliser type in determining EF1 (Flechard et al. 2007, Aguilera et al. 2013, Cayuela et al. 2017),
alternative emission factors that are disaggregated by climatic zone and fertiliser type are also provided. In wet
climates, the default value has been set at 0.6 percent of organic N inputs and 1.6 percent of synthetic N inputs. In
dry climates, the default value has been set at 0.5 percent of N inputs for both organic and synthetic N. These
alternative factor values for EF1 can be used by compilers that are able to disaggregate their activity data by
climate 9 and fertiliser type. There are data to suggest that the emission factor could also be further disaggregatedas part of a Tier 2 method. This disaggregation could be based on (1) environmental factors (soil organic C content,
soil texture, drainage, soil pH and climate such as temperature and freeze-thaw cycle); and (2) management-related
factors (N application rate per fertiliser type; fertiliser type, liquid or solid form of organic fertiliser; irrigation andtype of crop with differences between legumes, non-leguminous arable crops, and grass) (e.g. Cayuela et al. 2017,
Chadwick et al. 2018, Rochette et al. 2018, Wagner-Riddle et al. 2017).

9 Wet climates occur in temperate and boreal zones where the ratio of annual precipitation: potential evapotranspiration > 1,

and tropical zones where annual precipitation > 1000 mm. Dry climate occur in temperate and boreal zones where the ratioof annual precipitation: potential evapotranspiration < 1, and tropical zones where annual precipitation < 1000 mm (cf. Figure
3A.5.1 in Chapter 3 of Vol. 4 provides a map subdividing wet and dry climates based on these criteria).

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

TABLE 11.1 (UPDATED)DEFAULT EMISSION FACTORS TO ESTIMATE DIRECT N2O EMISSIONS FROM MANAGED SOILS
AggregatedEmission factor

Default
value

Uncertainty
range

EF1 for N additions fromsynthetic fertilisers, organic
amendments and crop
residues, and N mineralised
from mineral soil as a result ofloss of soil carbon1 [kg N2O–
N (kg N)-1]

0.010

EF1FR for flooded rice fields2,7[kg N2O–N (kg N)-1]

0.004

0.000 – 0.029

EF3PRP, CPP for cattle (dairy,
non-dairy and buffalo), poultry
and pigs3 [kg N2O–N (kg N)-1]

0.004

0.000– 0.014

EF3PRP, SO for sheep and ‘otheranimals’3 [kg N2O–N (kg N)-1]

0.003

0.000 – 0.010

0.002 – 0.018

Disaggregated
Disaggregation4

Default
value

Uncertainty
range

Synthetic fertiliser
inputs5 in wet climates

0.016

0.013 – 0.019

Other N inputs6 in wet
climates

0.006

0.001 – 0.011

All N inputs in dry
climates

0.005

0.000 – 0.011

Continuous flooding

0.003

0.000 – 0.010

Single and multiple
drainage

0.005

0.000 – 0.016

Wet climates

0.006

0.000 – 0.027

Dry climates

0.002

0.000 – 0.007

-

-

-

Sources:
Stehfest & Bouwman 2006; van Lent et al. 2015; Grace et al. 2016; van der Weerden et al. 2016; Albanito et al. 2017; Cayuela et al.
2017; Liu et al. 2017; Rochette et al. 2018.

1

2

Akiyama et al. 2005; Albanito et al. 2017; Cayuela et al. 2017.

Yamulki et al. 1998; Galbally et al. 2000; Liebig et al. 2008; Cai & Akiyama 2016; Cardenas et al. 2016; Di et al. 2016; Hoogendoorn etal. 2016; Hyde et al. 2016; Krol et al. 2016; Li et al. 2016; Luo et al. 2016; Marsden et al. 2016; Misselbrook et al. 2016; Nichols et al.
2016; O’Connor et al. 2016; Owens et al. 2016; Pelster et al. 2016; Ward et al. 2016; Balvert et al. 2017; Byrnes et al. 2017; Forrestal etal. 2017; Marsden et al. 2017; Owens et al. 2017; Thomas et al. 2017a, b; Tully et al. 2017; van der Weerden et al. 2017; Cardoso et al.
2018; Chadwick et al. 2018; Nichols et al. 2018.
3

4
Disaggregation of EF1 and EF3PRP, CPP by climate (based on long-term averages): Wet climates occur in temperate and boreal zones where
the ratio of annual precipitation: potential evapotranspiration > 1, and tropical zones where annual precipitation > 1000 mm. Dry climatesoccur in temperate and boreal zones where the ratio of annual precipitation: potential evapotranspiration < 1, and tropical zones whereannual precipitation < 1000 mm (cf. Figure 3A.5.1 in Chapter 3 of Vol. 4 provides a map subdividing wet and dry climates based on thesecriteria). In wet climates, the EF1 is further disaggregated by synthetic fertiliser N inputs and other N inputs.

This emission factor should be used for synthetic fertiliser applications, and fertiliser mixtures that include both synthetic and organic
forms of N.
5

6
Other N input refers to organic amendments, animal manures (e.g. slurries, digested manures), N in crop residues and mineralised N fromsoil organic matter decomposition.
7
Disaggregation of EF1FR: Single and multiple drainage also include alternate wetting and drying. Disaggregated EF1FR for rain-fed anddeep-water systems not provided due to lack of data. The EF1 should be used for upland rice.

Notes:
EF1: Uncertainty range of disaggregated EF1 based on the 95% confidence interval of fitted values. Uncertainty range of aggregated EF1 isbased on the 2.5th to 97.5th percentile of the dataset (See methods, data and results in Annex 11A.2).
EF1FR: Uncertainty range is based on the 2.5th to 97.5th percentile (See methods and data in Annex 11A.3).
EF3PRP, CPP and EF3PRP, SO: Uncertainty range is based on the 2.5th to 97.5th percentile (See methods and data in Annex 11A.4).
For EF2, see guidance in 2013 Supplement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories: Wetlands, Chapter 2,
Table 2.5.

Compilers that are able to disaggregate their activity data from all or some of these factors may choose to use
disaggregated emission factors with the Tier 2 approach.
The default value for EF3PRP is 0.4 percent of the N deposited by all animal types except ‘sheep’ and ‘other’ animals.
For these latter species, a default emission factor of 0.3 percent of the N deposited may be used 10. EF3PRP for cattle,

10 This is an update on the 2006 IPCC Guidelines, with over 400 cattle and sheep dung and urine EF values collated from 13
3countries (See Annex 11A.4). As noted in the 2006 IPCC Guidelines, reasons for the lower EF3PRP for sheep include moreeven urine distribution (smaller and more frequent urinations), and smaller effects on soil compaction during grazing. There
are no or very limited data for N2O emission factors of other animal types, and the emission factor for poultry and swine isassumed to be the same as for cattle. However, a value of 0.3% of the nitrogen deposited may be used for animals classified
as ‘other animals’ which includes goats, horses, mules, donkeys, camels, reindeer, and camelids, as these are likely to have2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

pigs and poultry (EF3PRP, CPP) is also disaggregated by wet and dry climates with values of 0.6 percent and 0.2
percent, respectively. There is no difference in EF3PRP for sheep and other animals (EF3PRP, SO) when disaggregatedinto wet and dry climates, therefore only an aggregated value is provided.

11.2.1.3 C HOICE OF ACTIVITY DATA
Tie r s 1 a nd 2
This section describes generic methods for estimating the amount of various N inputs to soils (FSN, FON, FPRP, FCR,
FSOM, FOS) that are needed for the Tier 1 and Tier 2 methodologies (Equations 11.1 and 11.2).
Applied synthetic fertiliser (FSN)
The term FSN refers to the annual amount of synthetic N fertiliser applied to soils 11. It is estimated from the total
amount of synthetic fertiliser consumed annually. Annual fertiliser consumption data may be collected fromofficial country statistics, often recorded as fertiliser sales and/or as domestic production and imports. If countryspecific data are not available, data can be used from the International Fertilizer Association (IFA)(http://www.fertilizer.org/ifa/statistics.asp) on total fertiliser use by type and by crop, or from the Food andAgriculture Organisation of the United Nations (FAO) (http://fao.org/faostat/) on synthetic fertiliser consumption.
It may be useful to compare national statistics to international databases such as those of the IFA and FAO. If
sufficient data are available, fertiliser use may be disaggregated by fertiliser type, crop type and climatic regime
for major crops. These data may be useful in developing revised emission estimates if inventory methods are
improved in the future. It should be noted that most data sources (including FAO) might limit reporting toagricultural N uses, although applications may also occur on Forest Land, Settlements, or other lands. This
unaccounted N is likely to account for a small proportion of the overall emissions. However, it is recommended
that countries seek out this additional information whenever possible.
Applied organic N fertilisers (FON)The term “applied organic N fertiliser” (FON) refers to the amount of organic N inputs applied to soils other thanby grazing animals and is calculated using Equation 11.3. This includes applied animal manure, sewage sludge
applied to soil, compost applied to soils, as well as other organic amendments of regional importance to agriculture(e.g., rendering waste, guano, brewery waste, etc.). Organic N fertiliser (FON) is calculated using Equation 11.3:
EQUATION 11.3
N FROM ORGANIC N ADDITIONS APPLIED TO SOILS (TIER 1)

FON = FAM + FSEW + FCOMP + FOOA
Where:
FON= total annual amount of organic N fertiliser applied to soils other than by grazing animals,
kg N yr-1

FAM= annual amount of animal manure N applied to soils, kg N yr-1

FSEW

= annual amount of total sewage N (coordinate with Waste Sector to ensure that sewage N is
not double-counted) that is applied to soils, kg N yr-1

FCOMP

= annual amount of total compost N applied to soils (ensure that manure N in compost is notdouble-counted), kg N yr-1

nitrogen excretion rates and patterns that are more similar to sheep than to cattle. For disaggregation of EF3 by dung andurine nitrogen for each livestock group, see Annex 11.4.
11 For the Tier 1 approach, the amounts of applied mineral nitrogen fertilisers (FSN) and of applied organic nitrogen fertilisers(FON) are no longer adjusted for the amounts of NH3 and NOx volatilisation after application to soil. This is a change fromthe methodology described in the Revised 1996 IPCC Guidelines. The reason for this change is that field studies that havedetermined N2O emission factors for applied N were not adjusted for volatilisation when they were estimated. In other words,
these emission factors were determined from: fertiliser-induced N2O–N emitted / total amount of N applied, and not from:fertiliser-induced N2O–N emitted / (total amount of N applied – NH3 and NOx volatilised). As a result, adjusting the amountof N input for volatilisation before multiplying it with the emission factor would in fact underestimate total N2O emissions.
Countries using Tier 2 or Tier 3 approaches should be aware that correction for NH3/NOx volatilisation after mineral ororganic N application to soil may be required depending on the emission factor and/or the inventory methodology used.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

FOOA= annual amount of other organic amendments used as fertiliser (e.g., rendering waste, guano,
brewery waste, etc.), kg N yr-1

The term FAM is determined by adjusting the amount of manure N available (NMMS_Avb; see Equation 10.34 in
Chapter 10) for the amount of managed manure used for feed (FracFEED), burned for fuel (FracFUEL), or used forconstruction (FracCNST) as shown in Equation 11.4. Data for FracFUEL, FracFEED, FracCNST can be obtained fromofficial statistics or a survey of experts. However, if these data are not available use NMMS_Avb as FAM without
adjusting for FracFUEL, FracFEED, FracCNST.
EQUATION 11.4
N FROM ANIMAL MANURE APPLIED TO SOILS (TIER 1)=
FAM N MMS Avb • 1 − ( FracFEED + FracFUEL + FracCNST ) 
Where:
FAM= annual amount of animal manure N applied to soils, kg N yr-1

N MMS Avb

= amount of managed manure N available for soil application, feed, fuel or construction, kg
N yr-1 (see Equation 10.34 in Chapter 10)

FracFEED= fraction of managed manure used for feed

FracFUEL= fraction of managed manure used for fuel

FracCNST= fraction of managed manure used for construction

Urine and dung from grazing animals (FPRP)The term FPRP refers to the annual amount of N deposited on pasture, range and paddock soils by grazing animals.
It is important to note that the N from managed animal manure applied to soils is included in the FAM term of FON.
The term FPRP is estimated using Equation 11.5 from the number of animals in each livestock species/category T(N(T)), the annual average amount of N excreted by each livestock species/category T (Nex(T)), and the fraction ofthis N deposited on pasture, range and paddock soils by each livestock species/category T (MS(T, PRP)). The dataneeded for this equation can be obtained from the livestock chapter (see Chapter 10, Section 10.5).
Equation 11.5 provides an estimate of the amount of N deposited by grazing animals:
EQUATION 11.5
N IN URINE AND DUNG DEPOSITED BY GRAZING ANIMALS ON PASTURE, RANGE AND PADDOCK(TIER 1)

FPRP=

∑ ( NT

(T )• Nex(T ) ) • MS(T , PRP ) 

Where:
FPRP= annual amount of urine and dung N deposited on pasture, range, paddock by grazing
animals, kg N yr-1

N (T )= number of head of livestock species/category T in the country (see Chapter 10, Section
10.2)

Nex(T )

= annual average N excretion per head of species/category T in the country, kg N animal-1 yr1MS(T , PRP )(see Chapter 10, Section 10.5)= fraction of total annual N excretion for each livestock species/category T that is depositedon pasture, range and paddock 12 (see Chapter 10, Section 10.5)

12 In the livestock section, pasture, range and paddock is referred to as one of the manure management systems denoted as “S”.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Crop residue N, including N-fixing crops and forage/ pasture renewal, returned to soils (FCR)
The term FCR refers to the amount of N in crop residues (above-ground and below-ground), including N-fixing
crops, returned to soils annually 13. It also includes the N from N-fixing and non-N-fixing forages11.16 mineralized
during forage or pasture renewal 14. It is estimated from crop yield statistics and default factors for above-/belowground residue:yield ratios and residue N contents. In addition, the method accounts for the effect of residue
burning or other removal of residues (direct emissions of N2O from residue burning are addressed under Chapter
2, Section 2.4). Because different crop types vary in residue:yield ratios, renewal time and N contents, separate
calculations should be performed for major crop types and then N values from all crop types are summed up. At aminimum, it is recommended that crops be segregated into: 1) non-N-fixing grain crops (e.g., maize, rice, wheat,barley); 2) N-fixing grains and pulses (e.g., soybean, dry beans, chickpea, lentils); 3) root and tuber crops (e.g.,
potato, sweet potato, cassava); 4) N-fixing forage crops (alfalfa, clover); and 5) other forages including perennial
grasses and grass/clover pastures. Equation 11.6 provides the equation to estimate N from crop residues andforage/pasture renewal, for a Tier 1 approach. As regards crop residue N, a cross check with the amount ofNbeddingMS of the Equation 10.34 “Managed manure N available for application to managed soils, feed, fuel orconstruction uses” (Volume 4, Chapter 10 Section 10.5.4) and biomass burning (Volume 4, Chapter 5 Section
5.2.4), relative to the amount of agricultural residues that is returned to soils other than the amount of agriculturalresidues that is removed for other purposes (e.g. bedding) or burnt should be done, in order to eliminate thepossibility of double counting.
EQUATION 11.6 (UPDATED)N FROM CROP RESIDUES AND FORAGE/PASTURE RENEWAL (TIER 1)=
FCR∑ { AGR • N
T(T )AG (T )()}

• 1 − FracRe move (T ) − ( FracBurnt (T ) • C f )  +  BGR(T ) • N BG (T )  
AGR(T ) = AGDM (T ) • Area(T )()

BGR(T ) = Crop(T ) + AGDM (T ) • RS(T ) • Area(T ) • FracRenew(T )AGDM (T ) = Crop(T ) • RAG (T )Where:
FCR= annual amount of N in crop residues (above and below ground), including N-fixing crops,
and from forage/pasture renewal, returned to soils annually, kg N yr-1

AGR(T )

= annual total amount of above-ground crop residue for crop T, kg d.m. yr-1.

N AG (T )= N content of above-ground residues for crop T, kg N (kg d.m.) -1 (Table 11.1a)

FracRe move (T ) = fraction of above-ground residues of crop T removed annually for purposes such as feed,

bedding and construction, dimensionless. Survey of experts in country is required to obtaindata. If data for FracRemove are not available, assume no removal
FracBurnt (T ) = fraction of annual harvested area of crop T burnt, dimensionlessCf= combustion factor (dimensionless) (refer to Chapter 2, Table 2.6)

BGR(T )

= annual total amount of belowground crop residue for crop T, kg d.m. yr-1

N BG (T )= N content of below-ground residues for crop T, kg N (kg d.m.)-1, (Table 11.1a)

AGDM (T )= Above-ground residue dry matter for crop T, kg d.m. ha-1

13 The equation to estimate F
CR has been modified from the Revised 1996 IPCC Guidelines to account for the contribution of

the below-ground nitrogen to the total input of nitrogen from crop residues, which previously was ignored in the estimate of
FCR. As a result, FCR now represents a more accurate estimate of the amount of nitrogen input from crop residue, whichmakes it possible to assess the contribution to residue nitrogen arising from the growth of forage legumes such as alfalfa,
where the harvesting of virtually all the above-ground dry matter results in no significant residue except the root system.

14 The inclusion of nitrogen from forage or pasture renewal is a change from the Revised 1996 IPCC Guidelines.

11.16

2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories

Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application(Use factors for RAG (T ) in Table 11.1a, or alternatively, AGDM (T ) may be estimated using the method anddata in Table 11.2)
Crop(T )= harvested annual dry matter yield for crop T, kg d.m. ha-1

RAG (T )= ratio of above-ground residue dry matter to harvested yield for crop T (Crop(T)), kg d.m. ha1

Area(T )(kg d.m. ha-1)-1, (Table 11.1a)= total annual area harvested of crop T, ha yr-1

FracRenew(T ) = fraction of total area under crop T that is renewed annually 15, dimensionless. For countries

where pastures are renewed on average every X years, FracRenew = 1/X. For annual crops
FracRenew = 1
RS(T )= ratio+ of below-ground root biomass to above-ground shoot biomass for crop T, kg d.m.
ha-1 (kg d.m. ha-1)-1, (Table 11.1a)T= crop or forage type

Data on crop yield statistics (yields and area harvested, by crop) may be obtained from national sources. If suchdata are not available, FAO publishes data on crop production: (http://fao.org/faostat/).
Since yield statistics for many crops are reported as field-dry or fresh weight, a correction factor should be applied
to estimate dry matter yields (Crop(T)) where appropriate (Equation 11.7). The proper correction to be used isdependent on the standards that are applied for yield reporting, which may vary between countries. Alternatively,
the default values for dry matter content given in Table 11.1a may be used.
EQUATION 11.7
DRY-WEIGHT CORRECTION OF REPORTED CROP YIELDS

Crop (T ) = Yield Fresh(T ) • DRY
Where:
Crop(T )= harvested dry matter yield for crop T, kg d.m. ha-1

Yield Fresh(T ) = harvested fresh yield for crop T, kg fresh weight ha-1

DRY

= dry matter fraction of harvested crop T, kg d.m. (kg fresh weight)-1

An improvement on this approach for determining FCR (i.e., Tier 2) would be the use of country-specific data rather
than the values provided in Table 11.1a, as well as country-specific values for the fraction of above-ground residue
burned.

15 This term is included in the equation to account for lower N release rates in grasslands that are not replanted annually (e.g.,van der Weerden et al., 1999; Davies et al., 2001).

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

TABLE 11.1A (NEW)DEFAULT VALUES FOR N AG(T), N BG(T), R AG(T), RS (T) AND DRY TO BE USED IN EQUATIONS 11.6 AND 11.7

Crops

N content ofabove-groundresidues

N content of
below-groundresidues

Ratio of aboveground residue
dry matter toharvested yield

Ratio ofbelow-groundbiomass toabove-groundbiomass

Dry matter
fraction of
harvested
product(N AG(T))a(N BG(T))a

(RAG (T))b

(RS (T))a(DRY)aCrops
Generic value forcrops not indicatedbelowc0.008 (± 75%)d

0.009 (± 75%)d

1.0

0.22

0.85

Generic Grains

0.006 (± 75%)d

0.009 (± 75%)d1.3

0.22 (±16%)0.88

Winter Wheat

0.006 (± 75%)d

0.009 (± 75%)d

1.3

0.23 (±41%)0.89

Spring Wheat

0.006 (± 75%)d

0.009 (± 75%)d

1.3

0.28 (±26%)

0.89

Barley0.007 (± 75%)d0.014 (± 75%)d1.2

0.22 (± 33%)

0.89

Oats

0.007 (± 75%)d

0.008 (± 75%)d1.3

0.25 (± 120%)

0.89

Maize

0.006 (± 75%)d

0.007 (± 75%)d1.00.22 (± 26%)

0.87

Rye

0.005 (± 75%)d0.011 (± 75%)d

1.6

-e

0.88

Rice

0.007 (± 75%)d

-e

1.4

0.16 (± 35%)

0.89

Millet0.007 (± 75%)d

-e

1.4

-e

0.90

Sorghum

0.007 (± 75%)d

0.006 (± 75%)d

1.4

-e

0.89

Beans and Pulses

0.008 (± 75%)d

0.008 (± 75%)d2.1

0.19 (± 45%)

0.91

Soybeans

0.008 (± 75%)d

0.008 (± 75%)d2.1

0.19 (± 45%)

0.91

Potatoes and Tubers

0.019 (± 75%)d0.014 (± 75%)d0.40.20 (± 50%)f

0.22

Peanuts

0.016 (± 75%)d

-e

1.0

-e

0.94

Alfalfa

0.027 (± 75%)d0.019 (± 75%)d-e

0.40 (± 50%)g

0.90

Non-legume hay

0.015 (± 75%)d

0.012 (± 75%)d-e

0.54 (± 50%)g

0.90

N-fixing forages

0.027 (± 75%)d

0.022 (± 75%)d0.3

0.40 (± 50%)

0.90

Non-N-fixing forages

0.015 (± 75%)d

0.012 (± 75%)d0.3

0.54 (± 50%)

0.90

Perennial Grasses

0.015 (± 75%)d

0.012 (± 75%)d0.30.80 (± 50%)h

0.90

Grass-Clover
Mixturesc

0.025 (± 75%)d0.016 (± 75%)d0.30.80 (± 50%)h

0.90

Sources:a
Literature review by Stephen A. Williams, Natural Resource Ecology Laboratory, Colorado State University. A list of the originalreferences is given in Annex 11A.1 of the 2006 IPCC Guidelines.
b
Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories (GPG2000). Chapter 4 Table 4.16 for R
AG(T) except forages, grasses and grass-clover mixes, which are from the 2006 IPCC Guidelines, Chapter 11, Table 11.2, and the genericvalue for all crops, which is the expert opinion of authors.
Notes:
It is assumed here that grass dominates the system by 2 to 1 over legumes.
d
No uncertainty is provided in the original study. This uncertainty is expert-based judgment.
e
No estimate is available. The most appropriate generic value can be used based on expert judgment, in absence of more specific information
available to develop a country-specific value.
fThis is an estimate of non-tuber roots based on the root:shoot values found for other crops. If unmarketable tuber yield is returned to thesoil then data derived from Vangessel & Renner 1990 (see Annex 11A.1 of the 2006 IPCC Guidelines) (unmarketable yield = 0.08 *marketable yield = 0.29 * above-ground biomass) suggest that the total residues returned might then be on the order of 0.49 * above-groundbiomass. Default s.d.
gThis is an estimate of root turnover in perennial systems. Default s.d.
hEstimate of root turnover to above-ground production based on the assumption that in natural grass systems below-ground biomass isapproximately equal to twice (one to three times) the above-ground biomass and that root turnover in these systems averages about 40%(30% to 50%) per year. Default s.d.
c

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

TABLE 11.2 (UPDATED)ALTERNATIVE METHOD AND DATA FOR ESTIMATING ABOVE-GROUND RESIDUE (AGDM(T))
Above-ground residue dry matter AGDM (T) (kg d.m. ha-1):
AGDM(T) = Crop(T) • Slope(T) + Intercept(T)Crop
Slope(T)± 2 s.d. as % of mean

Intercept(T)± 2 s.d. as % of mean

R2 adj.

Grains

1.09

± 2%

0.88

± 6%

0.65

Beans & pulsesb

1.13

± 19%

0.85

± 56%

0.28

Tubersc

0.10

± 69%

1.06

± 70%

0.18

Root crops, otherd

1.07

± 19%

1.54

± 41%

0.63

N-fixing forages

0.3± 50% default

0

-

-

Non-N-fixing forages

0.3± 50% default

0

-

-

Perennial grasses

0.3± 50% default

0

-

-

Grass-clover mixtures

0.3± 50% default

0

-

-

Maize

1.03

± 3%

0.61

± 19%

0.76

Wheat

1.51

± 3%

0.52

± 17%

0.68

Winter wheat

1.61

± 3%

0.40

± 25%

0.67

Spring wheat

1.29

± 5%

0.75

± 26%

0.76

Rice

0.95

±19%

2.46

± 41%

0.47

Barley

0.98

± 8%

0.59

± 41%

0.68

Oats

0.91

± 5%

0.89

± 8%

0.45

Millet

1.43

± 18%

0.14

± 308%

0.50

Sorghum

0.88

± 13%

1.33

± 27%

0.36

Ryee

1.09

± 50% default

0.88± 50% default-

Soybeanf

0.93

± 31%

1.35

± 49%

0.16

Dry beang

0.36± 100%

0.68

± 47%

0.15

Potatoh

0.10

± 69%

1.06

± 70%

0.18

Peanut (w/pod)i

1.07

± 19%

1.54

± 41%

0.63

Alfalfa

0.29j

± 31%

0

-

-

Non-legume hay

0.18± 50% default

0

-

-

Major crop types

Individual crops

Sources:a
Literature review by Stephen A. Williams, Natural Resource Ecology Laboratory, Colorado State University. A list of the originalreferences is given in Annex 11A.1 of the 2006 IPCC Guidelines.

Notes:b
The average above-ground residue:grain ratio from all data used was 2.0 and included data for soya bean, dry bean, lentil, cowpea, blackgram, and pea.
c

Average of other crops.

dModelled after peanuts.

e

No data for rye. Slope and intercept values are those for all grain. Default s.d.

f

The average above-ground residue:grain ratio from all data used was 1.9.

Ortega, 1988 (see Annex 11A.1 of the 2006 IPCC Guidelines). The average above-ground residue:grain ratio from this single source was
1.6. default s.d. for root:AGB.
gh

The mean value for above-ground residue: tuber ratio in the sources used was 0.27 with a standard error of 0.04.

i

The mean value for above-ground residue: pod yield in the sources used was 1.80 with a standard error of 0.10.

jThis is the average above-ground biomass reported as litter or harvest losses. This does not include reported stubble, which averaged 0.165* Reported Yields. Default s.d.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Mineralised N resulting from loss of soil organic C stocks in mineral soils through land-use change ormanagement practices (FSOM) 16
The term FSOM refers to the amount of N mineralised from loss in soil organic C in mineral soils through land-use
change or management practices. As explained in Chapter 2, Section 2.3.3, land-use change and a variety ofmanagement practices can have a significant impact on soil organic C storage. Organic C and N are intimately
linked in soil organic matter. Where soil C is lost through oxidation as a result of land-use or management change,
this loss will be accompanied by a simultaneous mineralisation of N. Where a loss of soil C occurs, this mineralised
N is regarded as an additional source of N available for conversion to N2O (Smith and Conen, 2004); just as
mineral N released from decomposition of crop residues, for example, becomes a source. The same default
emission factor (EF1) is applied to mineralised N from soil organic matter loss as is used for direct emissions
resulting from fertiliser and organic N inputs to agricultural land. This is because the ammonium and nitrate
resulting from soil organic matter mineralisation is of equal value as a substrate for the microorganisms producing
N2O by nitrification and denitrification, no matter whether the mineral N source is soil organic matter loss fromland-use or management change, decomposition of crop residues, synthetic fertilisers or organic amendments.
(Note: the opposite process to mineralisation, whereby inorganic N is sequestered into newly formed SOM, is nottaken account of in the calculation of the mineralisation N source. This is because of the different dynamics of
SOM decomposition and formation, and also because reduced tillage in some circumstances can increase both
SOM and N2O emission).
For all situations where soil C losses occur (as calculated in Chapter 2, Equation 2.25) the Tier 1 and 2 methods
for calculating the release of N by mineralisation are shown below:
Calculation steps for estimating changes in N supply from mineralisation
Step 1: Calculate the average annual loss of soil C (∆CMineral, LU) for the area, over the inventory period, using
Equation 2.25 in Chapter 2. Using the Tier 1 approach, the value for ∆CMineral, LU will have a single value for allland-uses and management systems. Using Tier 2, the value for ∆CMineral, LU will be disaggregated by individual
land-use and/or management systems.
Step 2: Estimate the N mineralised as a consequence of this loss of soil C (FSOM), using Equation 11.8:
EQUATION 11.8
N MINERALISED IN MINERAL SOILS AS A RESULT OF LOSS OF SOIL C THROUGH CHANGE IN LANDUSE OR MANAGEMENT (TIERS 1 AND 2)FSOM =∑  ∆C
LU

Mineral , LU•1
 • 1000 R

Where:
FSOM= the net annual amount of N mineralised in mineral soils as a result of loss of soil carbon
through change in land use or management, kg N

∆CMineral , LU = average annual loss of soil carbon for each land-use type (LU), tonnes C (Note: for

Approach 1 for land representation, ∆CMineral , LU will have a single value for all land-uses
and management systems. Using Approaches 2 and 3 for land representation the value for∆CMineral , LU will be disaggregated by individual land-use and/or management systems.
R= C:N ratio of the soil organic matter. A default value of 15 (uncertainty range from 10 to 30)
for the C:N ratio (R) may be used for situations involving land-use change from Forest Landor Grassland to Cropland, in the absence of more specific data for the area. A default valueof 10 (range from 8 to 15) may be used for situations involving management changes on
Cropland Remaining Cropland. C:N ratio can change over time, land use, or management
practice 17. If countries can document changes in C:N ratio, then different values can be usedover the time series, land use, or management practice.

LU= land-use and/or management system type

16 The inclusion of the term F
SOM is a change from the previous Revised 1996 IPCC Guidelines, which did not include the Nfrom mineralisation associated with a loss of soil organic C.

17 Information on C:N ratios in forest and cropped soils may be found in the following references: Aitkenhead-Peterson et al.

2005; Garten et al. 2000; John et al. 2005; Lobe et al. 2001; Snowdon et al. 2005, and other references cited by these authors.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Step 3: For Approach 1 for land representation, the value for FSOM is calculated in a single step. For Approaches
2 and 3 for land representation, FSOM is calculated by summing across all land-uses and/or management system
types (LU).
Countries that are not able to estimate gross changes of mineral soil C will create a bias in the N2O estimate, and
it is good practice to acknowledge this limitation in the reporting documentation. It is also good practice to use
specific data for the C:N ratios for the disaggregated land areas, if these are available, in conjunction with the datafor carbon changes.
Area of drained/managed organic soils (FOS)The term FOS refers to the total annual area (ha) of drained/managed organic soils (see footnote 3 for definition).
This definition is applicable for both the Tier 1 and Tier 2 methods. For all land uses, the areas should be stratified
by climate zone (temperate and tropical). In addition, for temperate Forest Land the areas should be further
stratified by soil fertility (nutrient rich and nutrient poor). The area of drained/managed organic soils (FOS) may becollected from official national statistics. Alternatively, total areas of organic soils from each country are available
from FAO (http://fao.org/faostat/), and expert judgement may be used to estimate areas that are drained/managed.
For Forest Land, national data will be available at soil survey organisations and from wetland surveys, e.g., forinternational conventions. In case no stratification by soil fertility is possible, countries may rely on expert
judgment.

11.2.1.4 U NCERTAINTY ASSESSMENT
No refinement.

11.2.2 Indirect N 2 O emissions
In addition to the direct emissions of N2O from managed soils that occur through a direct pathway (i.e., directlyfrom the soils to which N is applied), emissions of N2O also take place through two indirect pathways (i.e., ‘offsite’ N2O emission from N volatilisation/deposition and N leaching, as illustrated above in Section 11.2).
The first of these pathways is the volatilisation of N as NH3 and oxides of N (NOx), and the deposition of thesegases and their products NH4+ and NO3- onto soils and the surface of lakes and other waters. The sources of N as
NH3 and NOx are not confined to agricultural fertilisers and manures, but also include fossil fuel combustion,
biomass burning, and processes in the chemical industry (see Volume 1, Chapter 7, Section 7.3). Thus, theseprocesses cause N2O emissions in an exactly analogous way to those resulting from deposition of agriculturally
derived NH3 and NOx, following the application of synthetic and organic N fertilisers and /or urine and dungdeposition from grazing animals. The second pathway is the leaching and runoff from land of N from synthetic
and organic fertiliser additions, crop residues 18, mineralisation of N associated with loss of soil C in mineral anddrained/managed organic soils through land-use change or management practices, and urine and dung deposition
from grazing animals. Some of the inorganic N in or on the soil, mainly in the NO3- form, may bypass biologicalretention mechanisms in the soil/vegetation system by transport in overland water flow (runoff) and/or flow
through soil macropores or pipe drains. Where NO3- is present in the soil in excess of biological demand, e.g.,under cattle urine patches, the excess leaches through the soil profile. The nitrification and denitrification processes
described at the beginning of this chapter transform some of the NH4+ and NO3- to N2O. This may take place inthe groundwater below the land to which the N was applied, or in riparian zones receiving drain or runoff water,
or in the ditches, streams, rivers and estuaries (and their sediments) into which the land drainage water eventuallyflows.
This methodology described in this chapter addresses the following N sources of indirect N2O emissions frommanaged soils arising from agricultural inputs of N:• synthetic N fertilisers (FSN);• organic N applied as fertiliser (e.g., applied animal manure 19, compost, sewage sludge, rendering waste, waste
water effluent and other organic amendments) (FON);• urine and dung N deposited on pasture, range and paddock by grazing animals (FPRP);

18 Crop residues should be included as an N input into the leaching and runoff component.
19 Volatilisation and subsequent deposition of nitrogen from the manure in manure management systems is covered in the

manure management section of this volume.

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11.21

Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application• N in crop residues (above- and below-ground), including N-fixing crops and forage/pasture renewal returned
to soils (FCR) 20; and• N mineralisation associated with loss of soil organic matter resulting from change of land use or managementon mineral soils (FSOM).
The generic Tier 1 and Tier 2 methods described below can be used to estimate aggregate total indirect N2Oemissions from agricultural N additions to managed soils for an entire country. If a country is estimating its direct
N2O from managed soils by land-use category, the indirect N2O emissions can also be estimated by the same
disaggregation of land-use categories using the equations presented below with activity data, partitioning fractions,
and/or emission factors specific for each land-use category. The methodology for estimating indirect N2Oemissions from combustion-related and industrial sources is described in Volume 1, Chapter 7, Section 7.3.

11.2.2.1 C HOICE OF METHOD
Refer to the decision tree in Figure 11.3 (Indirect N2O Emissions) for guidance on which tier method to use.
Tie r 1Volatilisation, N2O(ATD)
The N2O emissions from atmospheric deposition of N volatilised from managed soil are estimated using Equation
11.9:
EQUATION 11.9
N2O FROM ATMOSPHERIC DEPOSITION OF N VOLATILISED FROM MANAGED SOILS (TIER 1)

N 2O( ATD ) −=N ( FSN • FracGASF ) + ( ( FON + FPRP ) • FracGASM )  • EF4
Where:

N 2 O( ATD ) −N = annual amount of N2O–N produced from atmospheric deposition of N volatilised frommanaged soils, kg N2O–N yr-1
FSN

= annual amount of synthetic fertiliser N applied to soils, kg N yr-1

FracGASF= fraction of synthetic fertiliser N that volatilises as NH3 and NOx, kg N volatilised (kg of N
applied)-1 (Table 11.3)

FON= annual amount of managed animal manure, compost, sewage sludge and other organic N
additions applied to soils, kg N yr-1

FPRP

= annual amount of urine and dung N deposited by grazing animals on pasture, range andpaddock, kg N yr-1

FracGASM= fraction of applied organic N fertiliser materials (FON) and of urine and dung N depositedby grazing animals (FPRP) that volatilises as NH3 and NOx, kg N volatilised (kg of N appliedor deposited)­1 (Table 11.3)

EF4= emission factor for N2O emissions from atmospheric deposition of N on soils and water
surfaces, [kg N–N2O (kg NH3–N + NOx–N volatilised)-1] (Table 11.3)

Conversion of N2O(ATD)-N emissions to N2O emissions for reporting purposes is performed by using the following
equation:
N2O(ATD) = N2O(ATD) –N * 44/28

20 Nitrogen from these components is only included in the leaching/run-off component of indirect N O emission.
2

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Figure 11.3

Decision tree for indirect N 2 O emissions from managed soils
Start

For each
agricultural N source1, for bothvolatilization and leaching/runoff, ask:
Do you have country-specificactivity data?

Is this a
key category2
and is this N source
significant3?

No

Obtain countryspecific data

Yes

For each N source, do
you have rigorously documented
country-specific emission factors (EF4 or EF5) and as
appropriate rigorously documented country-specificpartitioning fractions (FracGASF,
Frac,GASM, FracLEACH)
values?

Yes

Yes
No

Do youhave rigorously documented countryspecific EF values (EF4 or EF5) and as appropriate
rigorously documented country-specific partitioning
fractions (FracGASF, FracGASM, FracLEACH)
values?

Yes

No

Estimate emissions using Tier 2equation, country-specific activity dataand country-specific emissions factors
and partitioning fractions, or Tier 3
methodEstimate emissions with Tier 2equation, using a mix of countryspecific and other available data andcountry-specific emission andpartitioning factors

Box 4: Tier 2 or 3

Box 2: Tier 2

No

Estimate emissions using Tier 1 or Tier
2 equations, country-specific activity
data and a mix of county-specific or
default emission factors andpartitioning fractions

Estimate emissions using the Tier 1
equation with default emission andpartitioning factors and available
activity data

Box 3: Tier 1 or 2

Box 1: Tier 1

Note
1: N sources include: synthetic N fertilizer, organic N additions, urine and dung depositions, crop residue, N mineralization/immobilization associated with loss/
gain of soil C on mineral soils as a result of land use change or management practices (crop residue and N mineralization/immobilization is only accounted for in
the indirect N2O emissions from leaching/runoff). Sewage sludge or other organic N additions can be included if sufficient information is available.
2: See Volume 1 Chapter 4, "Methodological Choice and Identification of Key Categories" (noting Section 4.1.2 on limited resources), for discussion of key
categories and use of decision trees.
3: As a rule of thumb, a sub-source category would be significant if it accounts for 25-30% of emissions from the source category.

Leaching/Runoff, N2O(L)The N2O emissions from leaching and runoff in regions where leaching and runoff occurs are estimated using
Equation 11.10:
EQUATION 11.10
N2O FROM N LEACHING/RUNOFF FROM MANAGED SOILS IN REGIONS WHERE LEACHING/RUNOFF
OCCURS (TIER 1)

N 2O( L ) −N=( FSN + FON + FPRP + FCR + FSOM ) • FracLEACH −( H ) • EF5

Where:

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

N 2 O( L ) −N

= annual amount of N2O–N produced from leaching and runoff of N additions tomanaged
soils in regions where leaching/runoff occurs, kg N2O–N yr-1

FSN

= annual amount of synthetic fertiliser N applied to soils in regions where leaching/runoff
occurs, kg N yr-1

FON

= annual amount of managed animal manure, compost, sewage sludge and other organic N
additions applied to soils in regions where leaching/runoff occurs, kg N yr-1

FPRP

= annual amount of urine and dung N deposited by grazing animals in regions whereleaching/runoff occurs, kg N yr-1 (from Equation 11.5)

FCR= amount of N in crop residues (above- and below-ground), including N-fixing crops, andfrom forage/pasture renewal, returned to soils annually in regions where leaching/runoff
occurs, kg N yr-1

FSOM

= annual amount of N mineralised in mineral soils associated with loss of soil C from soilorganic matter as a result of changes to land use or management in regions whereleaching/runoff occurs, kg N yr-1 (from Equation 11.8)

FracLEACH − ( H ) = fraction of all N added to/mineralised in managed soils in regions where leaching/runoff
occurs that is lost through leaching and runoff, kg N (kg of N additions)-1 (Table 11.3)= emission factor for N2O emissions from N leaching and runoff, kg N2O–N (kg N leachedand runoff)­1 (Table 11.3)

EF5

Note: If a country is able to estimate the quantity of N mineralised from organic soils, then include this as anadditional input to Equation 11.10.
Conversion of N2O(L)–N emissions to N2O emissions for reporting purposes is performed by using the following
equation:
N2O(L) = N2O(L)–N ● 44/28
Tie r 2
If more detailed emission, volatilisation or leaching factors are available to a country than are presented in Table
11.3, further disaggregation of the terms in the equations can also be undertaken. For example, if specificvolatilisation factors are available for the application of synthetic fertilisers (FSN) under different conditions i,
Equation 11.9 would be expanded to become 21:
EQUATION 11.11
N2O FROM ATMOSPHERIC DEPOSITION OF N VOLATILISED FROM MANAGED SOILS (TIER 2)
N 2O( ATD=∑ FSNi • FracGASFi + ( FON + FPRP ) • FracGASM   • EF4
) −N
 i


(

)

Where:

N 2 O( ATD ) −N = annual amount of N2O–N produced from atmospheric deposition of N volatilised frommanaged soils, kg N2O–N yr-1
FSNi

= annual amount of synthetic fertiliser N applied to soils under different conditions i, kg N
yr-1

FracGASFi= fraction of synthetic fertiliser N that volatilises as NH3 and NOx under different conditions
i, kg N volatilised (kg of N applied)-1

21 It is important to note that Equation 11.11 is just one of many possible modifications to Equation 11.9, and is also meant toillustrate how Equation 11.10 could be modified, when using the Tier 2 method. The eventual form of Equation 11.11 will
depend upon the availability of land use and/or condition-specific partitioning fractions and/or emission factors and the ability
to which a country can disaggregate its activity data.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

FON= annual amount of managed animal manure, compost, sewage sludge and other organic N
additions applied to soils, kg N yr-1

FPRP

= annual amount of urine and dung N deposited by grazing animals on pasture, range andpaddock, kg N yr-1

FracGASM= fraction of applied organic N fertiliser materials (FON) and of urine and dung N depositedby grazing animals (FPRP) that volatilises as NH3 and NOx, kg N volatilised (kg of N appliedor deposited)­1 (Table 11.3)

EF4= emission factor for N2O emissions from atmospheric deposition of N on soils and water
surfaces, [kg N–N2O (kg NH3–N + NOx–N volatilised)-1] (Table 11.3)

Countries can also develop emission factors for FracGASF and FracGASM that are specific for mitigation options suchas the application of urease inhibitors.
Conversion of N2O(ATD)–N emissions to N2O(ATD) emissions for reporting purposes is performed by using thefollowing equation:

N 2O( ATD ) = N 2O( ATD ) – N • 44 / 28
Tie r 3Tier 3 methods are modelling or measurement approaches. Models are useful as they can relate the variables
responsible for the emissions to the size of those emissions. These relationships may then be used to predict
emissions from whole countries or regions for which experimental measurements are impracticable. For more
information refer to Chapter 2, Section 2.5, where guidance is given that provides a sound scientific basis for thedevelopment of a Tier 3 Model-based system.
According to Equations 11.1, 11.9 and 11.10, direct and indirect emissions of N2O from managed soils arecalculated in the Tier 1 approach on the basis of total N applied to soils as synthetic and organic fertilisers and/or
soil N mineralisation. As noted in Section 11.2.1.1, the processes of run-off of N, volatilization of NH3 and NOx,emissions of N2O, and leaching of N, however, do not occur simultaneously but in a sequence, with the peak of
run-off and NH3+NOx volatilization happening before emissions of N2O and losses of N through leaching. Refer
to Section 11.2.1.1 for good practice guidance when implementing a Tier 3 approach and adopting the N-flow
principle when estimating direct N2O emissions and indirect N2O emissions from leaching and runoff.

11.2.2.2 C HOICE OF EMISSION , VOLATILISATION AND LEACHING
FACTORSThe method for estimating indirect N2O emissions includes two emission factors: one associated with volatilised
and re-deposited N (EF4), and the second associated with N lost through leaching/runoff (EF5). The method also
requires values for the fractions of N that are lost through volatilisation (FracGASF and FracGASM) or leaching/runoff(FracLEACH-(H)). The default values of all these factors are presented in Table 11.3.
Note that in the Tier 1 method, for wet climates 22 or in dry climate regions where irrigation (other than drip
irrigation) is used, the default FracLEACH-(H) is 0.24. For dry climates, the default FracLEACH-(H) is zero. The climate
threshold for FracLEACH-(H) can be refined at Tier 2 by countries that are able to disaggregate their activity data (seemethodological suggestion in Table 11.3).
Country-specific values for EF4 should be used with great caution because of the special complexity oftransboundary atmospheric transport. Although inventory compilers may have specific measurements of N
deposition and associated N2O flux, in many cases the deposited N may not have originated in their country.
Similarly, some of the N that volatilises in their country may be transported to and deposited in another country,
where different conditions that affect the fraction emitted as N2O may prevail. For these reasons the value of EF4
is very difficult to determine, and the method presented in Volume 1, Chapter 7, Section 7.3 attributes all indirect
N2O emissions resulting from inputs to managed soils to the country of origin of the atmospheric NOx and NH3,
rather than the country to which the atmospheric N may have been transported.

22 Wet climates occur in temperate and boreal zones where the ratio of annual precipitation: potential evapotranspiration > 1,

and tropical zones where annual precipitation > 1000 mm. Dry climate occur in temperate and boreal zones where the ratioof annual precipitation: potential evapotranspiration < 1, and tropical zones where annual precipitation < 1000 mm (cf. Figure
3A.5.1 in Chapter 3 of Vol. 4 provides a map subdividing wet and dry climates based on these criteria).

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

TABLE 11.3 (UPDATED)DEFAULT EMISSION, VOLATILISATION AND LEACHING FACTORS FOR INDIRECT SOIL N2O EMISSIONS
AggregatedFactorDefault
value

Uncertainty
range

EF4 [N volatilisation and redeposition]1, kg N2O–N (kg NH3–N+ NOx–N volatilised)-1

0.010

0.002 - 0.018

EF5 [leaching/runoff]2, kg N2O–N(kg N leaching/runoff)-1

0.011

0.000 - 0.020

FracGASF[Volatilisation
fromsynthetic fertiliser]3, (kg NH3–N +NOx–N) (kg N applied)–1

0.11

0.02 - 0.33

DisaggregatedDefault
value

Uncertainty
range

Wet climate

0.014

0.011 – 0.017

Dry climate

0.005

0.000 – 0.011

-

-

Urea

0.15

0.03 – 0.43

Ammonium-based

0.08

0.02 – 0.30

Nitrate-based

0.01

0.00 – 0.02

Ammonium-nitrate-based

0.05

0.00 – 0.20

Disaggregation-

FracGASM [Volatilisation from allorganic N fertilisers applied, anddung and urine deposited by grazing
animals]4, (kg NH3–N + NOx–N)(kg N applied or deposited)–1

0.21

0.00 - 0.31

-

-

-

FracLEACH-(H)[N
lossesbyleaching/runoff in wet climates]5, kg
N (kg N additions or deposition bygrazing animals)-1

0.24

0.01 – 0.73

-

-

-

Sources:1
Stehfest & Bouwman 2006; van Lent et al. 2015; Grace et al. 2016; van der Weerden et al. 2016; Albanito et al. 2017; Cayuela et al.
2017; Liu et al. 2017; Rochette et al. 2018.
2

Tian et al. 2019.

3

NH3: Bouwman et al. 2002; Pan et al. 2016. NOx: Liu et al. 2017.

4

NH3: Bouwman et al. 2002; Cai & Akiyama 2016. NOx: Liu et al. 2017.

Reviews: Di & Cameron 2002; Cai & Akiyama 2016. Original papers: Moreno et al. 1996; Diez et al. 1997; Catt et al. 1998; Sogbedji etal. 2000; Asadi et al. 2002; Readman et al. 2002; Ren et al. 2003; Dauden & Quilez 2004; Dauden et al. 2004; Diez et al. 2004; Bakhsh etal. 2005; Basso & Ritchie 2005; Gehl et al. 2005; Fang et al. 2006; Li et al. 2006; Diez-Lopez et al. 2008; Conrad & Fohrer 2009; Zhu etal. 2009; Aronsson & Stenberg 2010; Bakhsh et al. 2010; Salmeron et al. 2010; Yague & Quilez 2010; Claret et al. 2011; Huang et al.
2011; Gallejones et al. 2012; Perego et al. 2012; Sorensen & Rubaek 2012; Tafteh & Sepaskhah 2012; Wang et al. 2012.
5

Notes:Disaggregation by climate for EF4 and FracLEACH-(H) (based on long-term averages): Wet climates occur in temperate and boreal zones where
the ratio of annual precipitation: potential evapotranspiration > 1, and tropical zones where annual precipitation > 1000 mm. Dry climatesoccur in temperate and boreal zones where the ratio of annual precipitation: potential evapotranspiration < 1, and tropical zones whereannual precipitation < 1000 mm (cf. Figure 3A.5.1 in Chapter 3 of Vol. 4).
EF4: The aggregated EF4 is the same as the aggregated EF1 (see Annex 11A.5). The disaggregated EF4 are the same as the EF1 disaggregatedby wet and dry climates (see Table A.2 in Annex11A.2). Uncertainty range of the aggregated EF4 is based on the 2.5th to 97.5th percentileof the dataset, uncertainty range of disaggregated EF4 is based on the 95% confidence interval of fitted values (See methods and data in
Annex 11A.2).
EF5: This emission factor incorporates three components: EF5 = EF5g + EF5r + EF5e. EF5g: Emission factor for groundwater and surface
drainage, including upstream supersaturated with N2O (N2O emitted mainly from degassing of groundwater); EF5r: Emission factor for
rivers and reservoirs, including downstream (supersaturated N2O was already degassed and N2O mainly produced bynitrification/denitrification in situ); EF5e: Emission factor for estuaries. See methods in Annex 11A.6. Uncertainty range is based on the
2.5th to 97.5th percentile.
FracGASF: Calculated by weighting world fertiliser usage with number of observations from review papers (See methods and data in Annex
11A.7). Uncertainty range based on the 2.5th to 97.5th percentile.
FracGASM: See methods in Annex 11A.8. Uncertainty range is based on the 2.5th to 97.5th percentile.
FracLEACH-(H): The FracLEACH-(H) only applies to wet climates. For dry climate, the default FracLEACH-(H) is taken as zero. See methods in Annex
11A.9. Uncertainty range is based on the 2.5th to 97.5th percentile.
For Tier 2, country specific FracLEACH-(H) can be estimated for N losses by leaching/runoff for regions where Σ(rain) - Σ(ET0) > soil water
holding capacity, OR where irrigation (except drip irrigation) is used. ET0 = Kpan * Ep, where ET0: reference evapotranspiration, Kpan:
pan evaporation coefficient, Ep: pan evaporatio n. When Kpan is not available, reference evaporation can be estimated as ET0= 0.5 * Ep
(Explanations of reference and pan evaporation: see Allen et al. 1998). Long-term mean of annual rainfall data should be used for estimating
FracLEACH-(H). Precipitation and potential evapotranspiration data are available from global datasets, such as the CRU climate dataset(https://crudata.uea.ac.uk/cru/data/hrg/), if country-specific data are not available.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

11.2.2.3 C HOICE OF ACTIVITY DATA
In order to estimate indirect N2O emissions from the various N additions to managed soils, the parameters FSN,
FON, FPRP, FCR, FSOM need to be estimated.
Applied synthetic fertiliser (FSN)
The term FSN refers to the annual amount of synthetic fertiliser N applied to soils. Refer to the activity data section
on direct N2O emissions from managed soils (Section 11.2.1.3) and obtain the value for FSN.
Applied organic N fertilisers (FON)The term FON refers to the amount of organic N fertiliser materials intentionally applied to soils. Refer to theactivity data section on direct N2O emissions from managed soils (Section 11.2.1.3) and obtain the value for FON.
Urine and dung from grazing animals (FPRP)The term FPRP refers to the amount of N deposited on soil by animals grazing on pasture, range and paddock. Referto the activity data section on direct N2O emissions from managed soils (Section 11.2.1.3) and obtain the value for
FPRP.
Crop residue N, including N from N-fixing crops and forage/pasture renewal, returned to soils (FCR)
The term FCR refers to the amount of N in crop residues (above- and below-ground), including N-fixing crops,
returned to soils annually. It also includes the N from N-fixing and non-N-fixing forages mineralised during
forage/pasture renewal. Refer to the activity data section on direct N2O emissions from managed soils (Section
11.2.1.3) and obtain the value for FCR.
Mineralised N resulting from loss of soil organic C stocks in mineral soils (FSOM)
The term FSOM refers to the amount of N mineralised from the loss of soil organic C in mineral soils through landuse change or management practices. Refer to the activity data section on direct N2O emissions from managed
soils (Section 11.2.1.3) and obtain the value for FSOM.

11.2.2.4 U NCERTAINTY ASSESSMENT
No refinement.

11.2.3 Completeness, Time series, QA/QC
No refinement.

11.3

CO 2 EMISSIONS FROM LIMINGNo refinement.

11.4

CO 2 EMISSIONS FROM UREA FERTILIZATIONNo refinement.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Annex 11A.1

References for crop residue data in Table 11.2

No refinement.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Annex 11A.2

Estimation of Default Emission Factor(s) for EF1

Material and methods
We extracted all studies from the databases by Stehfest & Bouwman (2006), van Lent et al. (2015), Grace et al.
(2016), van der Weerden et al. (2016), Albanito et al. (2017), Cayuela et al. (2017), Liu et al. (2017), and Rochette
et al. (2018) and excluded studies which:•Were non-peer-reviewed publications.

•

Were conducted in the laboratory and greenhouse, and modelling studies (only field studies were selected).

•

Were conducted in flooded rice fields (emissions from N inputs in flooded rice are estimated using the EF1FR).

•

Related to grazed soils where urine and/or dung were applied (emissions from urine/dung inputs in grazed
soils are estimated using the EF3PRP).

•

Related to enhanced synthetic or organic fertiliser either treated with inhibitors or coated, and•Were conducted on drained organic soils.

We further selected the cases from the source databases for which an emission factor had been or could becomputed using a control site as:

EF1i =N 2OTi − N 2OCi
Ni

Where N2OTi is the N2O flux during the experimental period due to the application of inputs Ni and otherunquantified sources of N; and N2OCi is the N2O flux during the experimental period at a control site due to othersources of N than Ni.
Climate (Temperate/Boreal Wet, Temperate/Boreal, Dry Tropical Wet, Tropical Dry) was assigned to most cases.
Temperate, boreal and tropical zones correspond to those defined in Chapter 3 of Vol. 4 in the 2006 IPCC
Guidelines. Wet climates occur in temperate and boreal zones where the ratio of annual precipitation: potential
evapotranspiration > 1, and tropical zones where annual precipitation > 1000 mm. Dry climates occur in temperate
and boreal zones where the ratio of annual precipitation: potential evapotranspiration < 1, and tropical zones whereannual precipitation < 1000 mm. Climates were also grouped at a lower level of disaggregation by distinguishing
dry climates from wet climates. Fertiliser was categorised as synthetic, organic or a mix of synthetic and organic
forms. At a less disaggregated level, fertiliser comprised two groups: organic and synthetic plus mixed forms offertilser.
The linear mixed-effect model approach was selected for developing the disaggregated emission factors to accountfor lack of independence among data from individual sites compared to data from different sites. A location
identification was assigned to all individual cases from experimental sites. Cases either with an identical coordinate
or being from a same reference with a same soil type and a same land use were considered a unique location. The
models included location identification as a random-effect, and climate, fertiliser or their interaction as fixedeffects. Influence of the length of the experiment, of the N application rate as well as influence of irrigation in dry
climates was evaluated by considering these 3 variables as fixed-effects. The length of the experiment (days) was
categorized into 5 classes as: ≤ 120, (120; 180], (180; 240], (240; 300], and > 300. The N application rate (kg N
ha-1 period-1) was categorized following the 6 classes: (0; 100], (100; 200], (200; 300], (300; 500], (500; 700], and> 700. Irrigation was categorized as “Yes” or “No”.
Means for the fixed-effects were compared using the LSD Fisher test to evaluate significant differences among
the disaggregated EF1 values, and only retain disaggregated values if significant. The confidence intervals for thepredicted values from the linear mixed effect model was used to quantify uncertainty in the disaggregated EF1.
The EF1 was disaggregated by climate and fertiliser with no distinction between fertiliser form in dry climates(EF1 Dry), but with a distinction between fertiliser form in wet climates (EF1 Wet O and EF1 Wet S + M) (seeResults section and Table 11.1). Due to the imbalanced dataset between climates and fertiliser forms (76% in wet
climate, 80% with synthetic plus mixed fertiliser form), the aggregated EF1 could not be estimated using a linear
mixed-effect model. Instead, a balanced distribution was derived with a bootstrapping method in which 1000
values were randomly selected from the distribution of each of the disaggregated EF1 values (EF1 Dry, EF1 Wet
O, EF1 Wet S + M). The estimate for the aggregated EF1 is the average from the resulting distribution and theconfidence interval was derived based on the 2.5th to 97.5th percentile of the dataset (n = 3000).

Results

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

The dataset was dominated by cases from Europe (34 percent) and North America (28 percent). Cases from Asia
represented 19 percent of all cases while Africa, Central-South America, and Oceania formed an equal share of
6−7 percent of the dataset.
The linear mixed-effect model analysis indicated no clear trend of decrease or increase of the EF1 according to thelength of the experimental period or the N application rate (Table 2A.1). Therefore, these criteria were notconsidered further in the analysis.
TABLE 2A.1
SAMPLE SIZE, MEAN, AND UNCERTAINTY RANGE OF THE EF1 DISAGGREGATED BY LENGTH OF THE
EXPERIMENT (DAYS) AND N APPLICATION RATE (KG N HA-1 PERIOD-1). A, B, C LETTERS INDICATE A
SIGNIFICANT DIFFERENCE BETWEEN MEANS WITHIN A DISAGGREGATION LEVEL BASED ON LSD FISHER TEST
Disaggregation by length of experiment

n

Mean

Uncertainty range

Significance

≤120

335

0.012

0.008 − 0.015

B(120, 180]

188

0.020

0.016 − 0.024(180, 240]

84

0.009

0.003 − 0.014(240, 300]40

-0.002-0.010 − 0.007

> 300

205

0.013

0.008 − 0.017

B

Disaggregation by N application rate

n

Mean

Uncertainty range

Significance(0, 100]

255

0.015

0.011 − 0.018

A(100, 200]

377

0.011

0.007 − 0.014

A(200, 300]

135

0.014

0.004 − 0.025

A(300, 500]

63

0.010

0.004 − 0.015

A(500, 700]

15

0.008

-0.002 − 0.018

A

> 700

11

0.013

0.009 − 0.017

A

C
B
A

The analysis yielded no significant difference in EF1 between the four climates as disaggregated by temperatureand rainfall (Table 2A.2). Disaggregation by rainfall pointed towards an EF1 significantly higher in wet climate
than in dry climate. In dry climate, irrigation led to a higher EF1 than when irrigation was not practiced. Irrigation
was practiced in most (63 percent) cases from dry climates, explaining the similarity between the EF1 for dry
climates and the EF1 for irrigated fields in dry climates. Lower EF1 for non-irrigated fields in dry climates may be
used at Tier 2 level by compilers that have the corresponding activity data.
Comparison between the three fertiliser forms (S: Synthetic, O: Organic, M: Mixed S+O) suggested that synthetic
and mixes of synthetic and organic forms could be grouped into a single category, while the EF1 for organic
fertiliser forms was significantly lower than the EF1 for synthetic fertilisers. The EF1 obtained from the interactionof climate disaggregated by rainfall and fertiliser with two levels of disaggregation (O and S + M) were similar indry climates. In wet climates, the EF1 of the S + M form was significantly higher than the EF1 for the organic form.
Based on these results, the EF1 was disaggregated by climate and fertiliser with no distinction between fertiliser
form in dry climates (EF1 Dry = 0.5 percent), but with a distinction between organic fertiliser (EF1 Wet O = 0.6 percent)and synthetic plus mixed fertiliser (EF1 Wet S + M = 1.6 percent) in wet climates. The aggregated EF1 computed fromthese disaggregated values amounted to 1.0 percent with an uncertainty range of 0.2 – 1.8 percent.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

TABLE 2A.2
SAMPLE SIZE, MEAN, AND UNCERTAINTY RANGE OF THE EF1 DISAGGREGATED BY CLIMATE, FERTILISER FORM AND
IRRIGATION PRACTICE. A, B LETTERS INDICATE A SIGNIFICANT DIFFERENCE BETWEEN MEANS WITHIN A DISAGGREGATIONLEVEL BASED ON LSD FISHER TEST
Disaggregation by climate (temperature, rainfall)

n

Mean

Uncertainty range

Temperate/boreal wet

526

0.013

0.007 − 0.019

A

B

Temperate/boreal dry

121

0.007

-0.002 − 0.015

AB

Tropical wet

122

0.014

0.011 − 0.018

Tropical dry

86

0.004

-0.004 – 0.013

Disaggregation by rainfall

n

Mean

Uncertainty range

Wet

648

0.014

0.011 – 0.017

Dry

207

0.005

0.000 – 0.011

Disaggregation by irrigation in dry climate

n

Mean

Uncertainty range

Irrigation

94

0.004

0.003 − 0.006

No irrigation

56

0.001

-0.001 − 0.003

Disaggregation by fertiliser form (S: Synthetic, O: Organic,
M: Mixed S+O) in wet climate

n

Mean

Uncertainty range

S

607

0.013

0.007 − 0.019

M

49

0.014

0.011 − 0.017

A

O

163

0.007

0.003 − 0.011

A

Disaggregation by climate (rainfall) and fertiliser form (S +M: Synthetic and Mixed S+O, O: Organic)

n

Mean

Uncertainty range

Wet S + M

509

0.016

0.013 − 0.019

Wet O

110

0.006

0.001 − 0.011

A

Dry S + M

147

0.005

-0.003 − 0.013

A

Dry O

53

0.005

-0.003 − 0.013

A2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories

SignificanceB
A
SignificanceB
A
SignificanceB
A
SignificanceB
B

Significance
B

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Annex 11A.3

Estimation of Default Emission Factor(s) forEF1FR

We extracted all studies with paddy rice field experiments that had a zero-N control from the databases by Akiyama
et al. (2005), Albanito et al. (2017) and Cayuela et al. (2017). We excluded studies which:•Were non-peer-reviewed publications;•

Were conducted in the laboratory and greenhouses, and modelling studies (only field studies were selected);•

Were conducted in upland rice fields;•

Were less than 70 days in duration;•

Related to grazed soils where urine and/or dung was applied; and•Related to manure or fertilizer treated with inhibitors.

The database contained 70 EF1FR values and the arithmetic mean was 0.4 percent. Water management strongly
affects N2O emission from paddy rice fields (Akiyama et al. 2005). Therefore, aggregated and disaggregatedvalues by water management were calculated based on arithmetic means and confidence intervals were constructed
to include 95 percent of the distribution of measured emissions. Arithmetic mean of ‘continuous flooding’ (0.3
percent, n = 44) was lower than ‘with single and multiple drainage’ (0.5 percent, n = 26). Only ‘continuous floodingand ‘with single and multiple drainage’ were considered for disaggregation of water management, because thenumber of available data were not adequate to evaluate other drivers. For example, other factors such as climate
were not considered due to limited number of data.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Annex 11A.4

Estimation of Default Emission Factor(s) for
EF3PRP

We combined the dataset recently collated by Cai & Akiyama (2016) with 27 additional studies to derive EF3PRP
factors (Yamulki et al. 1998; Galbally et al. 2005; Liebig et al. 2008; Cardenas et al. 2016; Di et al. 2016;
Hoogendoorn et al. 2016; Hyde et al. 2016; Krol et al. 2016; Li et al. 2016; Luo et al. 2016; Marsden et al. 2016;
Misselbrook et al. 2016; Nichols et al. 2016; O’Connor et al. 2016; Owens et al. 2016; Pelster et al. 2016; Ward
et al. 2016; Balvert et al. 2017; Byrnes et al. 2017; Forrestal et al. 2017; Marsden et al. 2017; Owens et al. 2017;
Thomas et al. 2017a, b; Tully et al. 2017; van der Weerden et al. 2017; Cardoso et al. 2018; Chadwick et al. 2018;
Nichols et al. 2018). We excluded studies which:•Were non-peer-reviewed publications;•

Were conducted in the laboratory and greenhouses, and modelling studies (only field studies were selected);•

Were conducted in flooded rice fields;•

Included fertiliser (manure or synthetic) additions;•

Were less than 30 days in duration; and•Related to excreta treated with inhibitors.

The updated dataset contained 461 EF3PRP values, with urine dominating the data, representing 326 (= 71 percent)of the values. Data were collated from studies where excreta was deposited onto either pasture or forage crops
such as brassicas or fodder beets. Nitrogen sources were dung, real urine and artificial urine. Artificial urine
represented a substantial number of data values (72).
Research has shown that increasing soil water content generally results in greater N2O production and emission
from urine patches (de Klein et al. 2003, van der Weerden et al. 2014). Therefore, EF3PRP data have beendisaggregated by climate (dry and wet) for compilers with suitable activity data to allow disaggregation of
livestock classes by climate. The division between wet and dry in the tropics is based on 1000 mm of precipitation(greater than 1000 mm equating with wet/moist climate), and the division in the temperate region is based on meanannual precipitation:potential evapotranspiration ratio of 1 (greater than 1 equating with a wet/moist climate).
There are currently insufficient observations in the dataset to allow further climate disaggregation. Aggregatedvalues are also provided for compilers that are not able to disaggregate PRP N inputs by climate.
Disaggregated excreta EF3PRP values for cattle in wet and dry climates and sheep in wet and dry climates were
calculated from the urine and dung EF3PRP values reported in Table 4A.1, assuming a urine:dung nitrogen ratio of
0.66:0.34 (Kelliher et al. 2014). Disaggregated and aggregated excreta EF3PRP values are shown in Table 11.1.
There was no difference in excreta EF3PRP for sheep when disaggregated into wet and dry climates, therefore only
an aggregated value is provided.
The 95 percent confidence intervals were calculated using the 2.5th and 97.5th percentile of the data. Where urine
and dung values have been aggregated to determine ‘excreta’ values, the 95 percent confidence intervals for urine
and dung values have been converted to a proportion of the mean (see Fig. 3.3b in Volume 1, Chapter 3‘Uncertainties’) and weighted according to the urine:dung nitrogen ratio. These weighted proportions were thenused to estimate the 2.5th and 97.5th percentile of the excreta values.
To determine whether there were significant differences in excreta EF3 values between different categories (e.g.
cattle vs. sheep), the data were analysed using a linear model. Excreta type (dung vs. urine vs. artificial urine),
livestock type (cattle vs. sheep), land use (pastoral vs. forage crop) and climate (wet vs. dry) were added as fixed
effects. There were very few data obtained from the same site, therefore site was not included in the model as arandom effect. Due to its non-normal distribution, however, data was log transformed using a log (x + a) approach,(where a = 0.25 percent). An a term was added due to the presence of several negative values.
Results showed a significant difference between real urine and artificial urine EF3PRP values (P = 0.05). However,
the analysis of data from two of the studies that included both real urine and artificial urine at similar N loads (deKlein et al. 2003; Chadwick et al. 2018) showed urine type (real vs artificial) had no significant effect on EF3PRP(P = 0.88, n = 16). On this basis, all artificial urine data were included, adding considerably more observations to
the dataset (i.e., 63 additional observations).
Excreta type and animal type were highly significant (both P < 0.001), while there was a significant interaction
between climate and animal type (P = 0.04). EF3PRP values for cattle and sheep dung and urine, in wet and dry
climates are shown in Table 4A.1.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Compilers may improve their inventories with a Tier 2 method if activity data can be partitioned into dung andurine to produce a country-specific urine:dung ratio. This methodology will require data on N content of different
forages and feeds and the amount of feed consumed by livestock (MPI, 2014).
TABLE 4A.1
EF VALUES FOR CATTLE AND SHEEP DUNG AND URINE, IN WET AND DRY CLIMATES
Livestock
type

CattleSheep

Excreta
type

Climate
Wet

Dry

mean

2.5th to 97.5th percentile, nA

mean

2.5th to 97.5th percentile, nA

Urine

0.00770.0003 – 0.0382, 279

0.00320.0003 – 0.0093, 11

Dung0.00130.0000 – 0.0053, 107

0.00070.0001 – 0.0012, 6
0.0004 – 0.0091, 13B-0.0001 – 0.0091, 7C

Urine

0.00390.0004 – 0.0180, 35

0.0031B

Dung

0.0004-0.0019 – 0.0027, 21

0.0021C

A The 2.5th to 97.5th percentile range reflect the 95% confidence interval for the mean.
B There were only two data for sheep urine in dry climates, with a mean value of 0.0027. Because this mean value wassimilar to the cattle urine in dry climates mean of 0.0032, data from both livestock types were pooled to allow a morerobust mean and confidence interval for sheep urine under dry conditions.
C The dataset contained a single data value for sheep dung in dry climates (0.0105); this single value was greater than all
the data for cattle dung in dry climates. To derive an approximation for a mean value and confidence interval for sheep
dung in dry climates, this single sheep dung value was combined with cattle dung data from dry climates.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Annex 11A.5

Estimation of Default Emission Factor(s) for EF4

In order to develop EF4 values, review papers on indirect N2O emission from N deposition were collected fromthe published literature. We found two types of review papers, as described below.
1.

Review papers on N addition experiments conducted in non-agricultural sites

In these experiments chemical N was applied to non-agricultural and non-wetland soil to simulate N deposition.
Soil N2O emissions were measured in a zero-N control site and in a N treated site. One key advantage of this typeof study is that N2O emissions from the zero-N control (N2O from N mineralisation, plant litter and N deposition)
could be removed by subtracting the associated emissions from the treatment plots. The EF was computed as:
EF (percent) = (N2O N treatment – N2O control) / N input * 100
However, the disadvantage is that N application rates are often higher than actual N deposition rates. Regardless,the estimated EF values from these studies were the same order of magnitude to the EF1 values estimated for thisreport (Table 5A.1), at least given that most of experiments relevant for estimating new EF4 factors were conductedin temperate wet climate zones.
TABLE 5A.1
RESULTS FROM REVIEW PAPERS ON N ADDITION EXPERIMENTS AT NON-AGRICULTURAL SITES
Referencesn

Mean EF (%)

SD

Note

Aronson & Allison (2012)

93

1.9

3.1

Data with measurement period of less than 90days were excluded.

Liu & Greaver (2009)

42

0.87

0.25

–

2. Review papers on N2O emission and N deposition conducted in non-agricultural sites
In these experiments N2O emission and N deposition were measured concurrently in non-agricultural and nonwetland sites, and the EF was calculated as follows:
EF (%) = N2O / N deposition * 100
The advantage of this type of study is that actual N deposition rates were measured at these sites. However, thedisadvantage is that EF does not exclude N2O from a zero-N control (N2O from N mineralisation), and therefore
the influence of N deposition could not be isolated from other sources of N2O emissions. In general, the EF valuesof these studies were higher than those from N addition experiments in non-agricultural sites (Table 5A.2),
probably because the resulting EFs did not exclude N2O from N mineralisation and plant litter as well as othersources of N inputs. This could cause double counting because the other sources of N are already addressed inother calculations for direct and indirect N2O emissions.
TABLE 5A.2
RESULTS FROM REVIEW PAPERS ON N2O EMISSIONS AND N DEPOSITION AT NON-AGRICULTURAL SITES
Referencesn

Mean EF (%)

SD

Note

Bühlmann et al. (2015)

57

7.0

8.7

Mean was calculated from Table S1

van der Gon & Bleeker (2005)

21

3.8

4.1

Weighted mean was calculated from Table 3

de Vries et al. (2011)

67

7.3

7.5

Estimated data were excluded

Therefore, considering that N addition experiments conducted in non-agricultural sites reported similar EF values
as EF1 results from our analysis, we decided to use the same emission factors as EF1 for EF4. Disaggregation is
only considered for climate type due to the absence of dependence of EF4 upon the form (organic or synthetic) oforiginal N input that volatilised. The EF4 was disaggregated by wet and dry climates, as indicated in Table 2A.2of Annex11A.2.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Annex 11A.6

Estimation of Default Emission Factor(s) for EF5

We collected peer-reviewed papers on EF5 for in situ field studies (Tian et al. 2019). The final dataset contained
254 data observations (EF5g: n = 101, EF5r: n = 91, EF5e: n = 23).
The EF5g, EF5r and EF5e are defined as:
EF5g: groundwater (soil solution and lysimeter leaching water were not included), spring, surface drainage, andupstream emissions (upstream supersaturated with N2O, N2O emitted mainly from degassing of groundwater).
EF5r: rivers, reservoirs (including lake and pond), and downstream emissions (supersaturated N2O was alreadydegassed and N2O mainly produced by nitrification/denitrification in situ).
EF5e: estuary emissions (only including inner estuaries or lower reaches of river that are close to the river mouth,
while outer estuaries and coastal seawater are excluded).
We found a lack of consistency in dividing EF5g and EF5r for streams based on the literature, at least in somestudies. Here, we categorized data into EF5g based on upstream supersaturated with N2O where N2O is emitted
mainly from degassing of groundwater, and EF5r based on downstream, supersaturated N2O that was alreadydegassed and N2O mainly produced by nitrification/denitrification in situ.
Note that the N sources in most rivers include both agricultural (mainly arable farming and grazing grassland) andurban sewage. However, we found it was difficult to separate the different N sources based on the limited
information in the publications. Therefore, our dataset on EF5r includes non-agricultural N source.
Most estuaries are impacted by urban waste water and aquaculture in addition to agriculture. However, all available
data were included because of their limited number.
Arithmetic mean emission factors were calculated as follows; EF5g: 0.0060 kg N2O–N/kg NO3-N in the water,
EF5r: 0.0026 kg N2O–N/kg NO3-N in the water and EF5e: 0.0026 kg N2O–N/kg NO3-N in the water.
EF5 was calculated as follows:
EF5 = EF5g + EF5r + EF5e
Uncertainty range is based on the 2.5th to 97.5th percentile.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Annex 11A.7

Estimation of Default Factor(s) for FracGASF

The Tier 1 aggregated default NH3 + NOx EF for emissions from synthetic fertiliser has been derived as thearithmetic mean of default EF values for the different types of individual N fertilisers. Individual fertiliser types
were weighted according to their use in the period 2007-2015 as reported by the International Fertilizer Industry
Association (IFA) (Table 7A.1), based on world fertiliser usage. For countries that require inventories for air
pollutant emissions, there is a continuous update of NH3 and NO EF values through the EMEP/EEA air pollutant
emission inventory guidebook (European Environment Agency, 2016).
TABLE 7A.1
FERTILISER CONSUMPTION IN THE PERIOD 2007-2015 EXPRESSED AS THOUSAND TONNES NUTRIENTS AND % OF
TOTAL FERTILISER CONSUMED (SOURCE: IFA: HTTP://IFADATA.FERTILIZER.ORG/ )Fertiliser product2007-2015%

Ammonia (direct application)

35823

4

AS

27931

3

Urea

442550

50

AN

53676

6

CAN

29624

3

Nitrogen solutions

46870

5

Other N straight

45722

5

AP

55692

6

Other NP (N)

17911

2

N K compound (N)

2372

0.3

N P K compound (N)12722714

Where Ammonia (direct application) = anhydrous ammonia, AS= ammonium sulphate, AN=Ammonium nitrate,
CAN= calcium ammonium nitrate and AP= ammonium phosphate

For disaggregation, we divided all fertiliser usage into 4 types of fertiliser categories based on their basic chemicalcomposition: urea, ammonium-based (ammonia-direct application, AS, and AP), nitrate-based (N K compoundN) and ammonium-nitrate-based (AN, CAN, Nitrogen solutions, Other N straight, Other NP-N and N P K
compound-N). For weighting purposes, assumptions on chemical compositions had to be considered for different
fertiliser types reported by IFA for compound fertilisers and for those fertilisers that had not been tested in our
experimental datasets. We assumed that emissions from these fertiliser types were those obtained from the meanvalue of a mix of different straight fertilisers for different IFA fertiliser products, in the absence of clear statistics
on their composition and based on qualitative assessments (Table 7A.2).
TABLE 7A.2
ASSUMPTIONS ON THE POTENTIAL MIX OF DIFFERENT IFA FERTILISER PRODUCTS
Fertiliser productFertiliser Mix

Nitrogen solutions

Urea (50%), AN (25%), CAN (25%)

Other N straightAN (50%), CAN (50%)

Other NP (N)AN (50%), CAN (50%)

AP

MAP (50%), DAP (50%)

N K compound (N)Sodium Nitrate

N P K compound (N)AN (50%), CAN (50%)

Where AN = Ammonium nitrate, CAN = calcium ammonium nitrate AS = ammonium sulphate, AP = ammonium
phosphate, MAP = monoammonium phosphate and DAP = diammonium phosphate.

For NH3, we used the datasets of peer-reviewed studies from the Bouwman et al. (2002) meta-analysis and therecently published dataset collated by Pan et al. (2016). A total number of 273 studies were used, and included
most of the common fertiliser types. Although data were primarily obtained from studies comparing NH3 emissions
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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Applicationfrom different fertiliser types, we also included emissions data from other studies that were conducted for otherpurposes (e.g., assessing effect of urease inhibitors, application rate, and amendments) by using the EF values
from the control treatments.
For NOx, we used the dataset of peer-reviewed studies collated by Liu et al. (2017). For the Tier 1 EF, we usedthe data from 54 studies (171 field measurements) comprising information on NO emissions by aggregating datafrom all types of fertiliser. Furthermore, to develop the disaggregated NOx EFs, we estimated values that were
specific to different fertiliser types.
Median EF values for each fertiliser type for both NH3 and NOx are shown in Table 7A.3. Median instead of meanvalues were used due to skewed right distribution of the data.
TABLE 7A.3
EMISSION FACTORS FOR % NH3–N AND NOX-N (N APPLIED)–1 FROM DIFFERENT FERTILISER TYPES RESULTINGFROM TWO META-ANALYSIS AND NUMBER OF STUDIES INVOLVED
Fertiliser

Percentage lost as N (% )number of studies

Total

NH3-N

NOx-N

Total

NH3-N

NOx-N

Urea

15.3

14.2

1.1

209

187

22

AS

10.2

9.5

0.7

41

37

4

AN

6.0

3.0

2.9

34

23

11

CAN

3.2

1.6

1.6

7

6

1

DAP

9.8

9.1

0.7

11

8

3

MAP

6.0

5.3

0.7

3

2

1

Sodium Nitrate

1.2

0.2

1.0

4

1

3

AA

3

2.9

0.1

2

1

1

Where AS = ammonium sulphate, AN = Ammonium nitrate, CAN = calcium ammonium nitrate, DAP = diammonium
phosphate, MAP = monoammonium phosphate and AA = anhydrous ammonia.

EF values for NH3 emissions were compared with those obtained using the method to predict NH3 emissions in
the current EMEP/EEA guidelines (EMEP/EEA, 2016). The EF for NH3-N from urea (14.2 percent) is lower than
the range of 15.5-21 percent from current EMEP/EEA guidelines values, which depend on soil pH and temperature
conditions, but similar to Bouwman et al. (2002) and Pan et al. (2016) values. Discrepancies are likely to arise
based on the assumptions taken and analytical choices (e.g. use of mean vs. median). Moreover, it must be notedthat future revisions to the EMEP/EEA guidebook are expected to use most of the same data utilized in this report
and therefore, EFs may be updated in the EMEP/EEA guidebook (2016).

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Annex 11A.8

Estimation of Default Factor for FracGASM

Review papers on NH3 and NO were collected to derive the fraction of N that is volatilised. Field measurement
data with manure or slurry application and excreta patches were extracted from the published literature (see below).
Field measurement data with chemical N application as well as studies with a focus on mitigation technologies,
such as nitrification inhibitors or urease inhibitors were excluded from this analysis.
For NH3, the arithmetic mean was calculated from Bouwman et al. (2002) and Cai & Akiyama (2016). For NO,
the mean and uncertainty range were calculated from Cai & Akiyama (2016) and Liu et al. (2017). The difference
between mean EF for cattle and sheep excreta was negligible, thus livestock type was not considered. The default
FracGASM was derived as the sum of the arithmetic mean of NH3 EF and NOx EF. The uncertainty range was basedon 2.5th and 97.5th percentile.
TABLE 8A.1
EMISSION FACTORS FOR NH3–N AND NOX-N (N APPLIED OR DEPOSITED)–1
FROM MANURE APPLICATION AND EXCRETA PATCHES

n

Mean

Range
(2.5th to 97.5th percentile)

Source of data

NOx

40

0.015

0 – 0.149

Liu et al. (2017)

NH3

172

0.197

0 – 0.295

Bouwman et al. (2002), Cai & Akiyama (2016)

NOx + NH3

212

0.212

0 – 0.312

References listed above

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

Annex 11A.9

Estimation of Default Factor for FracLEACH-(H)

We collected review papers (Di & Cameron 2002; Cai & Akiyama 2016) and original papers on N leaching/runoff
for this analysis (Moreno et al. 1996; Diez et al. 1997; Catt et al. 1998; Sogbedji et al. 2000; Asadi et al. 2002;
Readman et al. 2002; Ren et al. 2003; Dauden & Quilez 2004; Dauden et al. 2004; Diez et al. 2004; Bakhsh et al.
2005; Basso & Ritchie 2005; Gehl et al. 2005; Fang et al. 2006; Li et al. 2006; Diez-Lopez et al. 2008; Conrad &Fohrer 2009; Zhu et al. 2009; Aronsson & Stenberg 2010; Bakhsh et al. 2010; Salmeron et al. 2010; Yague &Quilez 2010; Claret et al. 2011; Huang et al. 2011; Gallejones et al. 2012; Perego et al. 2012; Sorensen & Rubaek
2012; Tafteh & Sepaskhah 2012; Wang et al. 2012). Only peer-reviewed studies that used lysimeters and in-situ
field measurements were included. Studies conducted in the laboratory were excluded, along with studies that used
mitigation technologies such as nitrification inhibitor. The final dataset contained 355 data observations fromwhich the arithmetic mean and uncertainty range for a 95 percent confidence interval were calculated.

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Chapter 11: N2O Emissions from Managed Soils, and CO2 Emissions from Lime and Urea Application

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