Sources of nitrous oxide and fate of mineral nitrogen in sub-Arctic permafrost peat soils

Abstract. Nitrous oxide (N2O) emissions from permafrost-affected terrestrial ecosystems have received little attention, largely because they have been thought to be negligible. Recent studies, however, have shown that there are habitats in subarctic tundra emitting N2O at high rates, such as bare peat surfaces on permafrost peatlands. The processes behind N2O production in these high-emitting habitats are, however, poorly understood. In this study, we established an in situ 15N-labelling experiment with the main objectives to partition the microbial sources of N2O emitted from bare peat surfaces (BP) on permafrost peatlands and to study the fate of ammonium and nitrate in these soils and in adjacent vegetated peat surfaces (VP) showing low N2O emissions. Our results confirm the hypothesis that denitrification is mostly responsible for the high N2O emissions from BP surfaces. During the study period denitrification contributed with ~79 % of the total N2O emission in BP, while the contribution of ammonia oxidation was less, about 19 %. However, nitrification is a key process for the overall N2O production in these soils with negligible external nitrogen (N) load because it is responsible for nitrite/nitrate supply for denitrification, as also supported by relatively high gross nitrification rates in BP. Generally, both gross N mineralization and gross nitrification rates were much higher in BP with high N2O emissions than in VP, where the high C / N ratio together with low water content was likely limiting N mineralization and nitrification and, consequently, N2O production. Also, competition for mineral N between plants and microbes was additionally limiting N availability for N2O production in VP. Our results show that multiple factors control N2O production in permafrost peatlands, the absence of plants being a key factor together with inter-mediate to high water content and low C / N ratio, all factors which also impact on gross N turnover rates. The intermediate to high soil water content which creates anaerobic microsites in BP is a key N2O emission driver for the prevalence of denitrification to occur. This knowledge is important for evaluating future permafrost –N feedback loops from the Arctic.

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Nitrous oxide emission from Australian agricultural lands and mitigation options: a review

Soil Research ◽

10.1071/sr02064 ◽

2003 ◽

Vol 41 (2) ◽

pp. 165 ◽

Cited By ~ 379

Author(s):

Ram C. Dalal ◽

Weijin Wang ◽

G. Philip Robertson ◽

William J. Parton

Keyword(s):

Nitrous Oxide ◽

Global Warming ◽

N2o Emission ◽

Nitrous Oxide Emissions ◽

N2o Emissions ◽

Tropical Savannas ◽

Agricultural Lands ◽

Mineral N ◽

N2o Production ◽

Mitigation Options

Increases in the concentrations of greenhouse gases, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and halocarbons in the atmosphere due to human activities are associated with global climate change. The concentration of N2O has increased by 16% since 1750. Although atmospheric concentration of N2O is much smaller (314 ppb in 1998) than of CO2 (365 ppm), its global warming potential (cumulative radiative forcing) is 296 times that of the latter in a 100-year time horizon. Currently, it contributes about 6% of the overall global warming effect but its contribution from the agricultural sector is about 16%. Of that, almost 80% of N2O is emitted from Australian agricultural lands, originating from N fertilisers (32%), soil disturbance (38%), and animal waste (30%). Nitrous oxide is primarily produced in soil by the activities of microorganisms during nitrification, and denitrification processes. The ratio of N2O to N2 production depends on oxygen supply or water-filled pore space, decomposable organic carbon, N substrate supply, temperature, and pH and salinity. N2O production from soil is sporadic both in time and space, and therefore, it is a challenge to scale up the measurements of N2O emission from a given location and time to regional and national levels.Estimates of N2O emissions from various agricultural systems vary widely. For example, in flooded rice in the Riverina Plains, N2O emissions ranged from 0.02% to 1.4% of fertiliser N applied, whereas in irrigated sugarcane crops, 15.4% of fertiliser was lost over a 4-day period. Nitrous oxide emissions from fertilised dairy pasture soils in Victoria range from 6 to 11 kg N2O-N/ha, whereas in arable cereal cropping, N2O emissions range from <0.01% to 9.9% of N fertiliser applications. Nitrous oxide emissions from soil nitrite and nitrates resulting from residual fertiliser and legumes are rarely studied but probably exceed those from fertilisers, due to frequent wetting and drying cycles over a longer period and larger area. In ley cropping systems, significant N2O losses could occur, from the accumulation of mainly nitrate-N, following mineralisation of organic N from legume-based pastures. Extensive grazed pastures and rangelands contribute annually about 0.2 kg N/ha as N2O (93 kg/ha per year CO2-equivalent). Tropical savannas probably contribute an order of magnitude more, including that from frequent fires. Unfertilised forestry systems may emit less but the fertilised plantations emit more N2O than the extensive grazed pastures. However, currently there are limited data to quantify N2O losses in systems under ley cropping, tropical savannas, and forestry in Australia. Overall, there is a need to examine the emission factors used in estimating national N2O emissions; for example, 1.25% of fertiliser or animal-excreted N appearing as N2O (IPCC 1996). The primary consideration for mitigating N2O emissions from agricultural lands is to match the supply of mineral N (from fertiliser applications, legume-fixed N, organic matter, or manures) to its spatial and temporal needs by crops/pastures/trees. Thus, when appropriate, mineral N supply should be regulated through slow-release (urease and/or nitrification inhibitors, physical coatings, or high C/N ratio materials) or split fertiliser application. Also, N use could be maximised by balancing other nutrient supplies to plants. Moreover, non-legume cover crops could be used to take up residual mineral N following N-fertilised main crops or mineral N accumulated following legume leys. For manure management, the most effective practice is the early application and immediate incorporation of manure into soil to reduce direct N2O emissions as well as secondary emissions from deposition of ammonia volatilised from manure and urine.Current models such as DNDC and DAYCENT can be used to simulate N2O production from soil after parameterisation with the local data, and appropriate modification and verification against the measured N2O emissions under different management practices.In summary, improved estimates of N2O emission from agricultural lands and mitigation options can be achieved by a directed national research program that is of considerable duration, covers sampling season and climate, and combines different techniques (chamber and micrometeorological) using high precision analytical instruments and simulation modelling, under a range of strategic activities in the agriculture sector.

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Impacts of Nitrogen Addition on Nitrous Oxide Emission: Model-Data Comparison

10.5194/bg-2018-126 ◽

2018 ◽

Author(s):

Yujin Zhang ◽

Minna Ma ◽

Huajun Fang ◽

Dahe Qin ◽

Shulan Cheng ◽

...

Keyword(s):

Nitrous Oxide ◽

Global Climate ◽

Pore Space ◽

Terrestrial Ecosystem ◽

N2o Emission ◽

N Deposition ◽

N2o Emissions ◽

Emission Model ◽

N Addition ◽

N2o Production

Abstract. The contributions of long-lived nitrous oxide (N2O) to the global climate and environment have received increasing attention. Especially, atmospheric nitrogen (N) deposition has substantially increased in recent decades due to extensive use of fossil fuels in industry, which strongly stimulates the N2O emissions of the terrestrial ecosystem. Several models have been developed to simulate N2O emission, but there are still large differences in their N2O emission simulations and responses to atmospheric deposition over global or regional scales. Using observations from N addition experiments in a subtropical forest, this study compared six widely-used N2O models (i.e. DayCENT, DLEM, DNDC, DyN, NOE, and NGAS) to investigate their performances for reproducing N2O emission, and especially the impacts of two types of N additions (i.e. ammonium and nitrate: NH4+ and NO3−, respectively) and two levels (low and high) on N2O emission. In general, the six models reproduced the seasonal variations of N2O emission, but failed to reproduce relatively larger N2O emissions due to NH4+ compared to NO3− additions. Few models indicated larger N2O emission under high N addition levels for both NH4+ and NO3−. Moreover, there were substantial model differences for simulating the ratios of N2O emission from nitrification and denitrification processes due to disagreements in model structures and algorithms. This analysis highlights the need to improve representation of N2O production and diffusion, and the control of soil water-filled pore space on these processes in order to simulate the impacts of N deposition on N2O emission.

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Alteration of nitrous oxide emissions from floodplain soils by aggregate size, litter accumulation and plant–soil interactions

Biogeosciences ◽

10.5194/bg-15-7043-2018 ◽

2018 ◽

Vol 15 (22) ◽

pp. 7043-7057 ◽

Cited By ~ 3

Author(s):

Martin Ley ◽

Moritz F. Lehmann ◽

Pascal A. Niklaus ◽

Jörg Luster

Keyword(s):

Nitrous Oxide ◽

Leaf Litter ◽

Hot Spots ◽

Aggregate Size ◽

N2o Emission ◽

N2o Emissions ◽

N2o Production ◽

Plant Soil ◽

Floodplain Soils ◽

Plant Soil Interactions

Abstract. Semi-terrestrial soils such as floodplain soils are considered potential hot spots of nitrous oxide (N2O) emissions. Microhabitats in the soil – such as within and outside of aggregates, in the detritusphere, and/or in the rhizosphere – are considered to promote and preserve specific redox conditions. Yet our understanding of the relative effects of such microhabitats and their interactions on N2O production and consumption in soils is still incomplete. Therefore, we assessed the effect of aggregate size, buried leaf litter, and plant–soil interactions on the occurrence of enhanced N2O emissions under simulated flooding/drying conditions in a mesocosm experiment. We used two model soils with equivalent structure and texture, comprising macroaggregates (4000–250 µm) or microaggregates (<250 µm) from a N-rich floodplain soil. These model soils were planted with basket willow (Salix viminalis L.), mixed with leaf litter or left unamended. After 48 h of flooding, a period of enhanced N2O emissions occurred in all treatments. The unamended model soils with macroaggregates emitted significantly more N2O during this period than those with microaggregates. Litter addition modulated the temporal pattern of the N2O emission, leading to short-term peaks of high N2O fluxes at the beginning of the period of enhanced N2O emission. The presence of S. viminalis strongly suppressed the N2O emission from the macroaggregate model soil, masking any aggregate-size effect. Integration of the flux data with data on soil bulk density, moisture, redox potential and soil solution composition suggest that macroaggregates provided more favourable conditions for spatially coupled nitrification–denitrification, which are particularly conducive to net N2O production. The local increase in organic carbon in the detritusphere appears to first stimulate N2O emissions; but ultimately, respiration of the surplus organic matter shifts the system towards redox conditions where N2O reduction to N2 dominates. Similarly, the low emission rates in the planted soils can be best explained by root exudation of low-molecular-weight organic substances supporting complete denitrification in the anoxic zones, but also by the inhibition of denitrification in the zone, where rhizosphere aeration takes place. Together, our experiments highlight the importance of microhabitat formation in regulating oxygen (O2) content and the completeness of denitrification in soils during drying after saturation. Moreover, they will help to better predict the conditions under which hot spots, and “hot moments”, of enhanced N2O emissions are most likely to occur in hydrologically dynamic soil systems like floodplain soils.

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Sources of nitrous oxide emitted from European forest soils

Biogeosciences Discussions ◽

10.5194/bgd-2-1353-2005 ◽

2005 ◽

Vol 2 (5) ◽

pp. 1353-1380 ◽

Cited By ~ 1

Author(s):

P. Ambus ◽

S. Zechmeister-Boltenstern ◽

K. Butterbach-Bahl

Keyword(s):

Nitrous Oxide ◽

Forest Soils ◽

Forest Ecosystems ◽

C:N Ratio ◽

N Cycling ◽

Radiative Properties ◽

N2o Emissions ◽

Gross Nitrification ◽

N2o Production ◽

Average Contribution

Abstract. Forest ecosystems may provide strong sources of nitrous oxide (N2O), which is important for atmospheric chemical and radiative properties. Nonetheless, our understanding of controls on forest N2O emissions is insufficient to narrow current flux estimates, which still are associated with great uncertainties. In this study, we have investigated the quantitative and qualitative relationships between N-cycling and N2O production in European forests in order to evaluate the importance of nitrification and denitrification for N2O production. Soil samples were collected in 11 different sites characterized by variable climatic regimes and forest types. Soil N-cycling and associated production of N2O was assessed following application of 15N-labeled nitrogen. The N2O emission varied significantly among the different forest soils, and was inversely correlated to the soil C:N ratio. The N2O emissions were significantly higher from the deciduous soils (13 ng N2O-N cm-3d-1) than from the coniferous soils (4 ng N2O-N cm-3d-1). Nitrate (NO3-) was the dominant substrate for N2O with an average contribution of 62% and exceeding 50% at least once for all sites. The average contribution of ammonium (NH4+) to N2O averaged 34%. The N2O emissions were correlated with gross nitrification activities, and as for N2O, gross nitrification was also higher in deciduous soils (3.4 μ g N cm-3d-1) than in coniferous soils (1.1 μ g N cm-3d-1). The ratio between N2O production and gross nitrification averaged 0.67% (deciduous) and 0.44% (coniferous). Our study suggests that changes in forest composition in response to land use activities and global change may have implications for regional budgets of greenhouse gases. From the study it also became clear that N2O emissions were driven by the nitrification activity, although the N2O was produced per se mainly from denitrification. Increased nitrification in response to accelerated N inputs predicted for forest ecosystems in Europe may thus lead to increased greenhouse gas emissions from forest ecosystems.

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Dung and farm dairy effluent affect urine patch nitrous oxide emissions from a pasture

Animal Production Science ◽

10.1071/an15511 ◽

2016 ◽

Vol 56 (3) ◽

pp. 337 ◽

Cited By ~ 4

Author(s):

J. Li ◽

J. Luo ◽

Y. Shi ◽

Y. Li ◽

Y. Ma ◽

...

Keyword(s):

Nitrous Oxide ◽

Dairy Farm ◽

N2o Emission ◽

Nitrous Oxide Emissions ◽

N2o Emissions ◽

N2o Production ◽

Dairy Effluent ◽

Farm Dairy Effluent ◽

Urine Patch ◽

N2o Emission Factor

Urine patches in grazed pastures have been identified as important sources of nitrous oxide (N2O) emissions. An increase in N2O emissions is possible where urine patches coincide with dung patches and farm dairy effluent (FDE) applications. The aim of the present study was to quantify the effects of dung additions and fresh FDE applications on N2O emissions from urine patches. A field experiment was conducted on a pasture site at the AgResearch’s Ruakura dairy farm in Hamilton, New Zealand. A closed soil chamber technique was used to measure the N2O emissions from a free-draining volcanic soil that received urine (492 kg N/ha, simulated urine patches), with or without dung (1146 kg N/ha) and fresh FDE (100 kg N/ha) and to compare these with controls receiving no urine. The addition of dung delayed the peak N2O fluxes from the urine patches by ~30 days. This could be due to temporary nitrogen (N) immobilisation during decomposition of carbon from the dung. However, over the whole measurement period (271 days), dung addition increased the N2O emission factor (EF, % of applied N emitted as N2O) for the urine from 1.02% to 2.09%. The application of fresh FDE increased the EF to 1.40%. The effluent- or dung-induced increases in N2O emissions from the urine patches were possibly caused both by the direct input of N from effluent or dung and through the indirect priming effect of addition of dung or effluent on the availability of N from urine patches for N2O production. We conclude that when EFs are used in calculations of N2O emissions from urine, consideration should be given to the likelihood of coincidence with dung or FDE applications.

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Sources of nitrous oxide emitted from European forest soils

Biogeosciences ◽

10.5194/bg-3-135-2006 ◽

2006 ◽

Vol 3 (2) ◽

pp. 135-145 ◽

Cited By ~ 102

Author(s):

P. Ambus ◽

S. Zechmeister-Boltenstern ◽

K. Butterbach-Bahl

Keyword(s):

Nitrous Oxide ◽

Forest Soils ◽

Forest Ecosystems ◽

C:N Ratio ◽

N Cycling ◽

Radiative Properties ◽

N2o Emissions ◽

Gross Nitrification ◽

N2o Production ◽

Average Contribution

Abstract. Forest ecosystems may provide strong sources of nitrous oxide (N2O), which is important for atmospheric chemical and radiative properties. Nonetheless, our understanding of controls on forest N2O emissions is insufficient to narrow current flux estimates, which still are associated with great uncertainties. In this study, we have investigated the quantitative and qualitative relationships between N-cycling and N2O production in European forests in order to evaluate the importance of nitrification and denitrification for N2O production. Soil samples were collected in 11 different sites characterized by variable climatic regimes and forest types. Soil N-cycling and associated production of N2O was assessed following application of 15N-labeled nitrogen. The N2O emission varied significantly among the different forest soils, and was inversely correlated to the soil C:N ratio. The N2O emissions were significantly higher from the deciduous soils (13 ng N2O-N cm-3 d-1) than from the coniferous soils (4 ng N2O-N cm-3 d-1). Nitrate (NO3-) was the dominant substrate for N2O with an average contribution of 62% and exceeding 50% at least once for all sites. The average contribution of ammonium (NH4+) to N2O averaged 34%. The N2O emissions were correlated with gross nitrification activities, and as for N2O, gross nitrification was also higher in deciduous soils (3.4 µg N cm-3 d-1) than in coniferous soils (1.1 µg N cm-3 d-1). The ratio between N2O production and gross nitrification averaged 0.67% (deciduous) and 0.44% (coniferous). Our study suggests that changes in forest composition in response to land use activities and global change may have implications for regional budgets of greenhouse gases. From the study it also became clear that N2O emissions were driven by the nitrification activity, although the N2O was produced per se mainly from denitrification. Increased nitrification in response to accelerated N inputs predicted for forest ecosystems in Europe may thus lead to increased greenhouse gas emissions from forest ecosystems.

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Nitrous Oxide Emissions in Pineapple Cultivation on a Tropical Peat Soil

Sustainability ◽

10.3390/su13094928 ◽

2021 ◽

Vol 13 (9) ◽

pp. 4928

Author(s):

Alicia Vanessa Jeffary ◽

Osumanu Haruna Ahmed ◽

Roland Kueh Jui Heng ◽

Liza Nuriati Lim Kim Choo ◽

Latifah Omar ◽

...

Keyword(s):

Nitrous Oxide ◽

Soil Temperature ◽

Peat Soil ◽

Farming Systems ◽

N2o Emission ◽

Nitrous Oxide Emissions ◽

Natural State ◽

N2o Emissions ◽

Wet Season ◽

Peat Soils

Farming systems on peat soils are novel, considering the complexities of these organic soil. Since peat soils effectively capture greenhouse gases in their natural state, cultivating peat soils with annual or perennial crops such as pineapples necessitates the monitoring of nitrous oxide (N2O) emissions, especially from cultivated peat lands, due to a lack of data on N2O emissions. An on-farm experiment was carried out to determine the movement of N2O in pineapple production on peat soil. Additionally, the experiment was carried out to determine if the peat soil temperature and the N2O emissions were related. The chamber method was used to capture the N2O fluxes daily (for dry and wet seasons) after which gas chromatography was used to determine N2O followed by expressing the emission of this gas in t ha−1 yr−1. The movement of N2O horizontally (832 t N2O ha−1 yr−1) during the dry period was higher than in the wet period (599 t N2O ha−1 yr−1) because of C and N substrate in the peat soil, in addition to the fertilizer used in fertilizing the pineapple plants. The vertical movement of N2O (44 t N2O ha−1 yr−1) was higher in the dry season relative to N2O emission (38 t N2O ha−1 yr−1) during the wet season because of nitrification and denitrification of N fertilizer. The peat soil temperature did not affect the direction (horizontal and vertical) of the N2O emission, suggesting that these factors are not related. Therefore, it can be concluded that N2O movement in peat soils under pineapple cultivation on peat lands occurs horizontally and vertically, regardless of season, and there is a need to ensure minimum tilling of the cultivated peat soils to prevent them from being an N2O source instead of an N2O sink.

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Nitrogen and oxygen availabilities control water column nitrous oxide production during seasonal anoxia in the Chesapeake Bay

Biogeosciences ◽

10.5194/bg-15-6127-2018 ◽

2018 ◽

Vol 15 (20) ◽

pp. 6127-6138 ◽

Cited By ~ 3

Author(s):

Qixing Ji ◽

Claudia Frey ◽

Xin Sun ◽

Melanie Jackson ◽

Yea-Shine Lee ◽

...

Keyword(s):

Nitrous Oxide ◽

Chesapeake Bay ◽

Water Column ◽

N2o Emissions ◽

N2o Production ◽

Isotope Tracer ◽

Relative Contribution ◽

Environmental Controls ◽

Long Run ◽

Nitrate And Nitrite

Abstract. Nitrous oxide (N2O) is a greenhouse gas and an ozone depletion agent. Estuaries that are subject to seasonal anoxia are generally regarded as N2O sources. However, insufficient understanding of the environmental controls on N2O production results in large uncertainty about the estuarine contribution to the global N2O budget. Incubation experiments with nitrogen stable isotope tracer were used to investigate the geochemical factors controlling N2O production from denitrification in the Chesapeake Bay, the largest estuary in North America. The highest potential rates of water column N2O production via denitrification (7.5±1.2 nmol-N L−1 h−1) were detected during summer anoxia, during which oxidized nitrogen species (nitrate and nitrite) were absent from the water column. At the top of the anoxic layer, N2O production from denitrification was stimulated by addition of nitrate and nitrite. The relative contribution of nitrate and nitrite to N2O production was positively correlated with the ratio of nitrate to nitrite concentrations. Increased oxygen availability, up to 7 µmol L−1 oxygen, inhibited both N2O production and the reduction of nitrate to nitrite. In spring, high oxygen and low abundance of denitrifying microbes resulted in undetectable N2O production from denitrification. Thus, decreasing the nitrogen input into the Chesapeake Bay has two potential impacts on the N2O production: a lower availability of nitrogen substrates may mitigate short-term N2O emissions during summer anoxia; and, in the long-run (timescale of years), eutrophication will be alleviated and subsequent reoxygenation of the bay will further inhibit N2O production.

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

Biogeosciences ◽

10.5194/bg-9-2989-2012 ◽

2012 ◽

Vol 9 (8) ◽

pp. 2989-3002 ◽

Cited By ~ 18

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.

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Emission factors for estimating fertiliser-induced nitrous oxide emissions from clay soils in Australia’s irrigated cotton industry

Soil Research ◽

10.1071/sr16091 ◽

2016 ◽

Vol 54 (5) ◽

pp. 598 ◽

Cited By ~ 12

Author(s):

Peter Grace ◽

Iurii Shcherbak ◽

Ben Macdonald ◽

Clemens Scheer ◽

David Rowlings

Keyword(s):

Nitrous Oxide ◽

Meta Analysis ◽

Exponential Model ◽

N2o Emission ◽

Nitrous Oxide Emissions ◽

N2o Emissions ◽

Tier 2 ◽

Cotton Industry ◽

Greenhouse Gas Inventories ◽

N Rates

As a significant user of nitrogen (N) fertilisers, the Australian cotton industry is a major source of soil-derived nitrous oxide (N2O) emissions. A country-specific (Tier 2) fertiliser-induced emission factor (EF) can be used in national greenhouse gas inventories or in the development of N2O emissions offset methodologies provided the EFs are evidence based. A meta-analysis was performed using eight individual N2O emission studies from Australian cotton studies to estimate EFs. Annual N2O emissions from cotton grown on Vertosols ranged from 0.59kgNha–1 in a 0N control to 1.94kgNha–1 in a treatment receiving 270kgNha–1. Seasonal N2O estimates ranged from 0.51kgNha–1 in a 0N control to 10.64kgNha–1 in response to the addition of 320kgNha–1. A two-component (linear+exponential) statistical model, namely EF (%)=0.29+0.007(e0.037N – 1)/N, capped at 300kgNha–1 describes the N2O emissions from lower N rates better than an exponential model and aligns with an EF of 0.55% using a traditional linear regression model.

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