scholarly journals Nitrous oxide emission budgets and land-use-driven hotspots for organic soils in Europe

2014 ◽  
Vol 11 (23) ◽  
pp. 6595-6612 ◽  
Author(s):  
T. Leppelt ◽  
R. Dechow ◽  
S. Gebbert ◽  
A. Freibauer ◽  
A. Lohila ◽  
...  
Keyword(s):  
Land Use ◽  
Nitrous Oxide ◽  
Greenhouse Gas ◽  
Ph Value ◽  
Emission Factors ◽  
Organic Soils ◽  
N2o Emissions ◽  
The European Union ◽  
Study Results ◽  
N2o Fluxes

Abstract. Organic soils are a main source of direct emissions of nitrous oxide (N2O), an important greenhouse gas (GHG). Observed N2O emissions from organic soils are highly variable in space and time, which causes high uncertainties in national emission inventories. Those uncertainties could be reduced when relating the upscaling process to a priori-identified key drivers by using available N2O observations from plot scale in empirical approaches. We used the empirical fuzzy modelling approach MODE to identify main drivers for N2O and utilize them to predict the spatial emission pattern of European organic soils. We conducted a meta-study with a total amount of 659 annual N2O measurements, which was used to derive separate models for different land use types. We applied our models to available, spatially explicit input driver maps to upscale N2O emissions at European level and compared the inventory with recently published IPCC emission factors. The final statistical models explained up to 60% of the N2O variance. Our study results showed that cropland and grasslands emitted the highest N2O fluxes 0.98 ± 1.08 and 0.58 ± 1.03 g N2O-N m−2 a−1, respectively. High fluxes from cropland sites were mainly controlled by low soil pH value and deep-drained groundwater tables. Grassland hotspot emissions were strongly related to high amount of N-fertilizer inputs and warmer winter temperatures. In contrast, N2O fluxes from natural peatlands were predominantly low (0.07 ± 0.27 g N2O-N m−2 a−1) and we found no relationship with the tested drivers. The total inventory for direct N2O emissions from organic soils in Europe amount up to 149.5 Gg N2O-N a−1, which also included fluxes from forest and peat extraction sites and exceeds the inventory calculated by IPCC emission factors of 87.4 Gg N2O-N a−1. N2O emissions from organic soils represent up to 13% of total European N2O emissions reported in the European Union (EU) greenhouse gas inventory of 2011 from only 7% of the EU area. Thereby the model demonstrated that the major part (85%) of the inventory is induced by anthropogenic management, which shows the significant reduction potential by rewetting and extensification of agriculturally used peat soils.

scholarly journals Nitrous oxide emission hotspots from organic soils in Europe

2014 ◽  
Vol 11 (6) ◽  
pp. 9135-9182
Author(s):  
T. Leppelt ◽  
R. Dechow ◽  
S. Gebbert ◽  
A. Freibauer ◽  
A. Lohila ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Greenhouse Gas ◽  
Ph Value ◽  
A Priori ◽  
Emission Factors ◽  
Organic Soils ◽  
N2o Emissions ◽  
The European Union ◽  
Study Results ◽  
N2o Fluxes

Abstract. Organic soils are a main source of direct nitrous oxide (N2O) emissions, an important greenhouse gas (GHG). Observed N2O emissions from organic soils are highly variable in space and time which causes high uncertainties in national emission inventories. Those uncertainties could be reduced when relating the upscaling process to a priori identified key drivers by using available N2O observations from plot scale in empirical approaches. We used the empirical fuzzy modelling approach MODE to identify main drivers for N2O and utilize them to predict the spatial emission pattern of European organic soils. We conducted a meta study with a total amount of 659 annual N2O measurements which was used to derive separate models for different land use types. We applied our models to available, spatial explicit input driver maps to upscale N2O emissions on European level and compared the inventory with recently published IPCC emission factors. The final statistical models explained up to 60% of the N2O variance. Our study results showed that cropland and grasslands emitted the highest N2O fluxes 0.98 ± 1.08 and 0.58 ± 1.03 g N2O-N m−2 a−1, respectively. High fluxes from cropland sites were mainly controlled by low soil pH-value and deep drained groundwater tables. Grassland hotspot emissions were strongly related to high amount of N-fertilizer inputs and warmer winter temperatures. In contrast N2O fluxes from natural peatlands were predominantly low (0.07±0.27 g N2O-N m−2 a−1) and we found no relationship with the tested drivers. The total inventory for direct N2O emissions from organic soils in Europe amount up to 149.5 Gg N2O-N a−1, which included also fluxes from forest and peat extraction sites and exceeds the inventory calculated by IPCC emission factors of 87.4 Gg N2O-N a−1. N2O emissions from organic soils represent up to 13% of total European N2O emissions reported in the European Union (EU) greenhouse gas inventory of 2011 from only 7% of the EU area. Thereby the model demonstrated that with up to 85% the major part of the inventory is induced by anthropogenic management, which shows the significant reduction potential by rewetting and extensivation of agricultural used peat soils.

scholarly journals Spatial and temporal variability of nitrous oxide emissions in a mixed farming landscape of Denmark

2012 ◽  
Vol 9 (8) ◽  
pp. 2989-3002 ◽  
Author(s):  
K. Schelde ◽  
P. Cellier ◽  
T. Bertolini ◽  
T. Dalgaard ◽  
T. Weidinger ◽  
...  
Keyword(s):  
Land Use ◽  
Nitrous Oxide ◽  
Agricultural Land ◽  
Nitrous Oxide Emissions ◽  
Soil Conditions ◽  
Spatial And Temporal Variability ◽  
N2o Emissions ◽  
N2o Production ◽  
Mixed Farming ◽  
N2o Fluxes

Abstract. Nitrous oxide (N2O) emissions from agricultural land are variable at the landscape scale due to variability in land use, management, soil type, and topography. A field experiment was carried out in a typical mixed farming landscape in Denmark, to investigate the main drivers of variations in N2O emissions, measured using static chambers. Measurements were made over a period of 20 months, and sampling was intensified during two weeks in spring 2009 when chambers were installed at ten locations or fields to cover different crops and topography and slurry was applied to three of the fields. N2O emissions during spring 2009 were relatively low, with maximum values below 20 ng N m−2 s−1. This applied to all land use types including winter grain crops, grasslands, meadows, and wetlands. Slurry application to wheat fields resulted in short-lived two-fold increases in emissions. The moderate N2O fluxes and their moderate response to slurry application were attributed to dry soil conditions due to the absence of rain during the four previous weeks. Cumulative annual emissions from two arable fields that were both fertilized with mineral fertilizer and manure were large (17 kg N2O-N ha−1 yr−1 and 5.5 kg N2O-N ha−1 yr−1) during the previous year when soil water conditions were favourable for N2O production during the first month following fertilizer application. Our findings confirm the importance of weather conditions as well as nitrogen management on N2O fluxes.

scholarly journals Annual emissions of CH<sub>4</sub> and N<sub>2</sub>O, and ecosystem respiration, from eight organic soils in Western Denmark managed by agriculture

2012 ◽  
Vol 9 (1) ◽  
pp. 403-422 ◽  
Author(s):  
S. O. Petersen ◽  
C. C. Hoffmann ◽  
C.-M. Schäfer ◽  
G. Blicher-Mathiesen ◽  
L. Elsgaard ◽  
...  
Keyword(s):  
Land Use ◽  
Ecosystem Respiration ◽  
Spring Barley ◽  
Emission Factors ◽  
Climatic Conditions ◽  
Organic Soils ◽  
N2o Emissions ◽  
Sampling Points ◽  
Ch4 And N2o ◽  
Use Categories

Abstract. The use of organic soils by agriculture involves drainage and tillage, and the resulting increase in C and N turnover can significantly affect their greenhouse gas balance. This study estimated annual fluxes of CH4 and N2O, and ecosystem respiration (Reco), from eight organic soils managed by agriculture. The sites were located in three regions representing different landscape types and climatic conditions, and three land use categories were covered (arable crops, AR, grass in rotation, RG, and permanent grass, PG). The normal management at each site was followed, except that no N inputs occurred during the monitoring period from August 2008 to October 2009. The stratified sampling strategy further included six sampling points in three blocks at each site. Environmental variables (precipitation, PAR, air and soil temperature, soil moisture, groundwater level) were monitored continuously and during sampling campaigns, where also groundwater samples were taken for analysis. Gaseous fluxes were monitored on a three-weekly basis, giving 51, 49 and 38 field campaigns for land use categories AR, PG and RG, respectively. Climatic conditions in each region during monitoring were representative as compared to 20-yr averages. Peat layers were shallow, typically 0.5 to 1 m, and with a pH of 4 to 5. At six sites annual emissions of N2O were in the range 3 to 24 kg N2O-N ha−1, but at two arable sites (spring barley, potato) net emissions of 38 and 61 kg N2O-N ha−1 were recorded. The two high-emitting sites were characterized by fluctuating groundwater, low soil pH and elevated groundwater SO42− concentrations. Annual fluxes of CH4 were generally small, as expected, ranging from 2 to 4 kg CH4 ha−1. However, two permanent grasslands had tussocks of Juncus effusus L. (soft rush) in sampling points that were consistent sources of CH4 throughout the year. Emission factors for organic soils in rotation and with permanent grass, respectively, were estimated to be 0.011 and 0.47 g m−2 for CH4, and 2.5 and 0.5 g m−2 for N2O. This first documentation of CH4 and N2O emissions from managed organic soils in Denmark confirms the levels and wide ranges of emissions previously reported for the Nordic countries. However, the stratified experimental design also identified links between gaseous emissions and site-specific conditions with respect to soil, groundwater and vegetation which point to areas of future research that may account for part of the variability and hence lead to improved emission factors or models.

scholarly journals Nitrous oxide emissions at the landscape scale: spatial and temporal variability

2011 ◽  
Vol 8 (6) ◽  
pp. 11941-11978 ◽  
Author(s):  
K. Schelde ◽  
P. Cellier ◽  
T. Bertolini ◽  
T. Dalgaard ◽  
T. Weidinger ◽  
...  
Keyword(s):  
Land Use ◽  
Nitrous Oxide ◽  
Agricultural Land ◽  
Mineral Fertilizer ◽  
Landscape Scale ◽  
Nitrous Oxide Emissions ◽  
Spatial And Temporal Variability ◽  
N2o Emissions ◽  
N2o Production ◽  
N2o Fluxes

Abstract. Nitrous oxide (N2O) emissions from agricultural land are variable at the landscape scale due to variability in land use, management, soil type, and topography. A field experiment was carried out in a typical mixed farming landscape in Denmark, to investigate the main drivers of variations in N2O emissions, measured using static chambers. Measurements were done over a period of 20 months, and sampling was intensified during two weeks in spring 2009 when chambers were installed at ten locations or fields to cover different crops and topography and slurry was applied to three of the fields. N2O emissions during the spring 2009 period were relatively low, with maximum values below 20 ng N m−2 s−1. This applied to all land use types including winter grain crops, grassland, meadow, and wetland. Slurry application to wheat fields resulted in short-lived two-fold increases in emissions. The moderate N2O fluxes and their moderate response to slurry application were attributed to dry soil moisture conditions due to the absence of rain during the four previous weeks. Measured cumulated annual emissions from two arable fields that were both fertilized with mineral fertilizer and manure were large (17 kg N2O-N ha−1 yr−1 and 5.5 kg N2O-N ha−1 yr−1, respectively) during the previous year when soil water conditions were favourable for N2O production during the first month following fertilizer application, confirming the importance of the climatic regime on N2O fluxes.

scholarly journals Annual emissions of CH<sub>4</sub> and N<sub>2</sub>O, and ecosystem respiration, from eight organic soils in Western Denmark managed by agriculture

2011 ◽  
Vol 8 (5) ◽  
pp. 10017-10067 ◽  
Author(s):  
S. O. Petersen ◽  
C. C. Hoffmann ◽  
C.-M. Schäfer ◽  
G. Blicher-Mathiesen ◽  
L. Elsgaard ◽  
...  
Keyword(s):  
Land Use ◽  
Ecosystem Respiration ◽  
Spring Barley ◽  
Emission Factors ◽  
Climatic Conditions ◽  
Organic Soils ◽  
N2o Emissions ◽  
Sampling Points ◽  
Ch4 And N2o ◽  
Use Categories

Abstract. The use of organic soils by agriculture involves drainage and tillage, and the resulting increase in C and N turnover can significantly affect their greenhouse gas balance. This study estimated annual fluxes of CH4 and N2O, and ecosystem respiration (Reco), from eight organic soils managed by agriculture. The sites were located in three regions representing different landscape types and climatic conditions, and three land use categories (arable crops, AR, grass in rotation, RG, and permanent grass, PG) were covered. The normal management at each site was followed, except that no N inputs occurred during the monitoring period from August 2008 to October 2009. The stratified sampling strategy further included six sampling points in three blocks at each site. Environmental variables (precipitation, PAR, air and soil temperature, soil moisture, groundwater level) were monitored continuously and during sampling campaigns, where also groundwater samples were taken for analysis. Gaseous fluxes were monitored on a three-weekly basis, giving 51, 49 and 38 field campaigns for land use categories AR, PG and RG, respectively. Climatic conditions in each region during monitoring were representative based on 20-yr averages. Peat layers were shallow, typically 0.5 to 1 m, and with a pH of 4–5. At six sites annual emissions of N2O were in the range 3 to 24 kg N2O-N ha−1, but at two arable sites (spring barley, potato) net emissions of 38 and 61 kg N2O-N ha−1 were recorded. Both were characterized by fluctuating groundwater with elevated SO42− concentrations. Annual fluxes of CH4 were generally small, as expected, ranging from –2 to 4 kg CH4 ha−1. However, two permanent grasslands had tussocks of Juncus effusus (soft rush) in sampling points that were consistent sources of CH4 throughout the year. Emission factors for organic soils in rotation and permanent grass, respectively, were estimated to be 0.011 and 0.47 g m−2 for CH4, and 2.5 and 0.5 g m−2 for N2O. This first documentation of CH4 and N2O emissions from managed organic soils in Denmark confirms the levels and wide ranges of emissions previously reported for this region. However, the factorial approach also identified links between gaseous emissions and site-specific conditions with respect to soil, groundwater and vegetation which point to areas of future research that may account for part of the variability and hence lead to improved emission factors or models.

Emissions of nitrous oxide, ammonia and methane from Australian layer-hen manure storage with a mitigation strategy applied

2016 ◽  
Vol 56 (9) ◽  
pp. 1367 ◽  
Author(s):  
T. A. Naylor ◽  
S. G. Wiedemann ◽  
F. A. Phillips ◽  
B. Warren ◽  
E. J. McGahan ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Greenhouse Gas ◽  
Emission Factors ◽  
Control Treatment ◽  
N2o Emissions ◽  
Gaseous Emissions ◽  
Total N ◽  
Volatile Solids ◽  
Manure Storage ◽  
The Relationship

Greenhouse gas and ammonia emissions are important environmental impacts from manure management in the layer-hen industry. The present study aimed to quantify emissions of nitrous oxide (N2O), methane (CH4) and ammonia (NH3) from layer-hen manure stockpiles, and assess the use of an impermeable cover as an option to mitigate emissions. Gaseous emissions of N2O, CH4 and NH3 were measured using open-path FTIR spectroscopy and the emission strengths were inferred using a backward Lagrangian stochastic model. Emission factors were calculated from the relationship between gaseous emissions and stockpile inputs over a 32-day measurement period. Total NH3 emissions were 5.97 ± 0.399 kg/t (control) and 0.732 ± 0.116 kg/t (mitigation), representing an 88% reduction due to mitigation. Total CH4 emissions from the mitigation stockpile were 0.0832 ± 0.0198 kg/t. Methane emissions from the control and N2O emissions (control and mitigation) were below detection. The mass of each stockpile was 27 820 kg (control) and 25 120 kg (mitigation), with a surface area of ~68 m2 and a volume of ~19 m3. Total manure nitrogen (N) and volatile solids (VS) were 25.2 and 25.8 kg/t N, and 139 and 106 kg/t VS for the control and mitigation stockpiles respectively. Emission factors for NH3 were 24% and 3% of total N for the control and mitigation respectively. Methane from the mitigation stockpile had a CH4 conversion factor of 0.3%. The stockpile cover was found to reduce greenhouse gas emissions by 74% compared with the control treatment, primarily via reduced NH3 and associated indirect N2O emissions.

scholarly journals Stem and soil nitrous oxide fluxes from rainforest and cacao agroforest on highly weathered soils in the Congo Basin

2020 ◽  
Vol 17 (21) ◽  
pp. 5377-5397
Author(s):  
Najeeb Al-Amin Iddris ◽  
Marife D. Corre ◽  
Martin Yemefack ◽  
Oliver van Straaten ◽  
Edzo Veldkamp
Keyword(s):  
Land Use ◽  
Nitrous Oxide ◽  
Vapour Pressure Deficit ◽  
Congo Basin ◽  
Forest Conversion ◽  
N2o Emissions ◽  
Mineral N ◽  
Weathered Soils ◽  
N2o Fluxes ◽  
Highly Weathered Soils

Abstract. Although tree stems act as conduits for greenhouse gases (GHGs) produced in the soil, the magnitudes of tree contributions to total (soil + stem) nitrous oxide (N2O) emissions from tropical rainforests on heavily weathered soils remain unknown. Moreover, soil GHG fluxes are largely understudied in African rainforests, and the effects of land-use change on these gases are identified as an important research gap in the global GHG budget. In this study, we quantified the changes in stem and soil N2O fluxes with forest conversion to cacao agroforestry. Stem and soil N2O fluxes were measured monthly for a year (2017–2018) in four replicate plots per land use at three sites across central and southern Cameroon. Tree stems consistently emitted N2O throughout the measurement period and were positively correlated with soil N2O fluxes. 15N-isotope tracing from soil mineral N to stem-emitted 15N2O and correlations between temporal patterns of stem N2O emissions, soil–air N2O concentration, soil N2O emissions and vapour pressure deficit suggest that N2O emitted by the stems originated predominantly from N2O produced in the soil. Forest conversion to extensively managed, mature (>20 years old) cacao agroforestry had no effect on stem and soil N2O fluxes. The annual total N2O emissions were 1.55 ± 0.20 kg N ha−1 yr−1 from the forest and 1.15 ± 0.10 kg N ha−1 yr−1 from cacao agroforestry, with tree N2O emissions contributing 11 % to 38 % for forests and 8 % to 15 % for cacao agroforestry. These substantial contributions of tree stems to total N2O emissions highlight the importance of including tree-mediated fluxes in ecosystem GHG budgets. Taking into account that our study sites' biophysical characteristics represented two-thirds of the humid rainforests in the Congo Basin, we estimated a total N2O source strength for this region of 0.18 ± 0.05 Tg N2O-N yr−1.

scholarly journals Nitrous oxide fluxes from tropical peat with different disturbance history and management

2011 ◽  
Vol 8 (3) ◽  
pp. 5423-5450 ◽  
Author(s):  
J. Jauhiainen ◽  
H. Silvennoinen ◽  
R. Hämäläinen ◽  
K. Kusin ◽  
S. Limin ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Greenhouse Gas ◽  
N2o Emissions ◽  
Monitoring Methods ◽  
N2o Flux ◽  
Swamp Forest ◽  
Closed Chamber ◽  
Tropical Peat ◽  
C Stocks ◽  
N2o Fluxes

Abstract. Tropical peatlands are one of the most important terrestrial ecosystems in terms of C stocks, and greenhouse gas emissions following disturbances such as deforestation, drainage or wildfire. Nitrous oxide dynamics in tropical peat systems is still poorly known. We quantified in situ N2O fluxes using closed chamber methods and compared them with CO2 and CH4 fluxes at sites representing differing land uses and land use change intensities, i.e. non-drained and drained selectively logged peat swamp forest, clear-felled drained recovering forest, deforested drained and burned peat, and agriculture on peat. The mean N2O flux rates (N2O-N ± SD, mg m−2 h−1) varied as follows: drained forest (0.112 ± 0.293) > agricultural peat in Kalampangan site (0.012 ± 0.026) > drained burned peat (0.011 ± 0.018) > agricultural peat in Marang site (0.0072 ± 0.028) > nondrained forest (0.0025 ± 0.053) > clear-felled drained recovering forest (0.0022 ± 0.021). Most N2O fluxes were < 0.05 mg N2O-N m−2 h−1 efflux, but some modest peat N2O influx readings were also detected. Many very high flux rates (deviating markedly from the majority of observations) occurred both spatially and over time, and further studies using continuous flux monitoring methods are needed to better understand the contribution of these to cumulative emissions. The widest N2O flux amplitude was detected in the drained forest with moderately drained peat (max. 2.312 and min. −0.043 mg N2O-N m−2 h−1. At the other sites the flux amplitude remained about 10 × smaller. Annual cumulative peat surface N2O emissions expressed as CO2 equivalents as a percentage of the total greenhouse gas (N2O, CO2 and CH4) emissions was at the highest 9.2 %, but typically ~1 %.

Greenhouse gas emissions from dung, urine and dairy pond sludge applied to pasture. 1. Nitrous oxide emissions

2018 ◽  
Vol 58 (6) ◽  
pp. 1087 ◽  
Author(s):  
G. N. Ward ◽  
K. B. Kelly ◽  
J. W. Hollier
Keyword(s):  
Nitrous Oxide ◽  
Greenhouse Gas Emissions ◽  
Greenhouse Gas ◽  
Nitrification Inhibitor ◽  
Emission Factors ◽  
Nitrous Oxide Emissions ◽  
Cow Dung ◽  
N2o Emissions ◽  
Active Ingredients ◽  
Gas Emissions

Nitrous oxide (N2O) from excreta deposited by grazing ruminants is a major source of greenhouse gas emissions in Australia. Experiments to measure N2O emissions from dairy cow dung, urine and pond sludge applied to pasture, and the effectiveness of the nitrification inhibitor nitrapyrin in reducing these emissions, were conducted in south-western Victoria, Australia. In Experiment 1, emissions from urine, with and without nitrapyrin, and from dung were measured. Treatments applied in September 2013 resulted in cumulative emissions (245 days) of 0.60, 5.35, 4.15 and 1.02 kg N2O-nitrogen (N)/ha for the nil, urine (1000 kg N/ha), urine (1000 kg N/ha) + nitrapyrin (1 kg active ingredients/ha), and dung (448 kg N/ha) treatments, respectively, giving emission factors of 0.47% and 0.09% for urine and dung respectively. Nitrapyrin reduced N2O emissions from urine for 35 days, with an overall reduction in emissions of 25%. In Experiment 2, sludge, with and without nitrapyrin, was applied in May 2014, and dung was applied in May, August, November 2014 and January 2015. Cumulative emissions (350 days) were 0.19, 0.49, 0.31 and 0.39 kg N2O-N/ha for the nil, sludge (308 kg N/ha), sludge (308 kg N/ha) + nitrapyrin (1 kg active ingredients/ha), and dung (total 604 kg N/ha) treatments, respectively, giving emission factors of 0.10% and 0.03% for sludge and dung. Nitrapyrin reduced N2O emissions from sludge for 60 days, with an overall reduction in emissions of 59%. A third experiment on two soil types compared emissions from urine and dung, with and without nitrapyrin, applied in different seasons of the year. Emissions were highly seasonal and strongly related to soil water status. Emission factors (90 days) ranged from 0.02% to 0.19% for urine and 0.01% to 0.12% for dung. Nitrapyrin reduced emissions from urine by 0–35% and had little effect on emissions from dung. Overall, the experiments found that nitrapyrin was an effective tool in reducing emissions from urine, dung and sludge applied to pasture, but the magnitude varied across the year, with nitrapyrin being most effective when soils had >70% water-filled pore space when major emissions occurred.

scholarly journals UK emissions of the greenhouse gas nitrous oxide

2012 ◽  
Vol 367 (1593) ◽  
pp. 1175-1185 ◽  
Author(s):  
U. Skiba ◽  
S. K. Jones ◽  
U. Dragosits ◽  
J. Drewer ◽  
D. Fowler ◽  
...  
Keyword(s):  
Land Use ◽  
Nitrous Oxide ◽  
Greenhouse Gas ◽  
Emission Factor ◽  
Agricultural Sector ◽  
Emission Factors ◽  
Mitigation Strategies ◽  
Anthropogenic Source ◽  
Geographical Regions ◽  
Tier 1

Signatories of the Kyoto Protocol are obliged to submit annual accounts of their anthropogenic greenhouse gas emissions, which include nitrous oxide (N 2 O). Emissions from the sectors industry (3.8 Gg), energy (14.4 Gg), agriculture (86.8 Gg), wastewater (4.4 Gg), land use, land-use change and forestry (2.1 Gg) can be calculated by multiplying activity data (i.e. amount of fertilizer applied, animal numbers) with simple emission factors (Tier 1 approach), which are generally applied across wide geographical regions. The agricultural sector is the largest anthropogenic source of N 2 O in many countries and responsible for 75 per cent of UK N 2 O emissions. Microbial N 2 O production in nitrogen-fertilized soils (27.6 Gg), nitrogen-enriched waters (24.2 Gg) and manure storage systems (6.4 Gg) dominate agricultural emission budgets. For the agricultural sector, the Tier 1 emission factor approach is too simplistic to reflect local variations in climate, ecosystems and management, and is unable to take into account some of the mitigation strategies applied. This paper reviews deviations of observed emissions from those calculated using the simple emission factor approach for all anthropogenic sectors, briefly discusses the need to adopt specific emission factors that reflect regional variability in climate, soil type and management, and explains how bottom-up emission inventories can be verified by top-down modelling.

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