Insights into measuring highly variable and sporadic N2O emissions in a fertile peatland forest with automatic chambers

2020 ◽  
Author(s):  
Annalea Lohila ◽  
Mika Korkiakoski ◽  
Paavo Ojanen ◽  
Kari Minkkinen ◽  
Timo Penttilä ◽  
...  
Keyword(s):  
Peat Soil ◽  
N2o Emissions ◽  
Tree Stand ◽  
Temporal And Spatial Variability ◽  
Downy Birch ◽  
Soil Emissions ◽  
Temporal And Spatial ◽  
N2o Fluxes ◽  
Carbon Dioxide Co2 ◽  
Chamber Measurements

<p>Drainage and other management activities in peatlands make especially the fertile sites a source of greenhouse gases into the atmosphere. In addition to typically losing carbon dioxide (CO2) from the old peat, they act as sources of nitrous oxide (N2O) into the atmosphere. In contrary to CO2, N2O fluxes do not necessarily show a distinct seasonal cycle with high emissions in summer and low in winter. Instead, the most intense peaks in N2O fluxes have been earlier attributed to freezing-thawing cycles of peat soil. Emissions of N2O have been reported to vary greatly both in time and space. Due to instrument limitations, the fluxes have been typically measured using manual chamber technique which provides only a snapshot of the potentially highly dynamic fluxes.</p><p>In this presentation we show multi-year results of N2O fluxes captured by automatic chambers and compare those to temporally sparse manual chamber measurements. Our study site was a nutrient-rich drained peatland ‘Lettosuo’ located in Tammela in southern Finland. The peatland, originally an herb-rich tall sedge pine fen was drained for forestry in 1969. After that, the tree stand was a mixture of Scots pine, Norway spruce and Downy birch. N2O fluxes were measured hourly with six automatic chambers. We will address the temporal and spatial variability in the fluxes and the plausible reasons behind them, including the drought of summer 2018, and give a summary of the exploitability of different methods. Suggestions for an improved chamber configuration and for the optimal sampling frequency for manual chambers will be given based on the results.</p><p> </p><p> </p><p> </p>

scholarly journals Pineapple Residue Ash Reduces Carbon Dioxide and Nitrous Oxide Emissions in Pineapple Cultivation on Tropical Peat Soils at Saratok, Malaysia

2021 ◽  
Vol 13 (3) ◽  
pp. 1014
Author(s):  
Liza Nuriati Lim Kim Choo ◽  
Osumanu Haruna Ahmed ◽  
Nik Muhamad Nik Majid ◽  
Zakry Fitri Abd Aziz
Keyword(s):  
Carbon Dioxide ◽  
Nitrous Oxide ◽  
Peat Soil ◽  
Nitrous Oxide Emissions ◽  
N2o Emissions ◽  
Peat Soils ◽  
Closed Chamber ◽  
Npk Fertilizers ◽  
Npk Fertilizer ◽  
Carbon Dioxide Co2

Burning pineapple residues on peat soils before pineapple replanting raises concerns on hazards of peat fires. A study was conducted to determine whether ash produced from pineapple residues could be used to minimize carbon dioxide (CO2) and nitrous oxide (N2O) emissions in cultivated tropical peatlands. The effects of pineapple residue ash fertilization on CO2 and N2O emissions from a peat soil grown with pineapple were determined using closed chamber method with the following treatments: (i) 25, 50, 70, and 100% of the suggested rate of pineapple residue ash + NPK fertilizer, (ii) NPK fertilizer, and (iii) peat soil only. Soils treated with pineapple residue ash (25%) decreased CO2 and N2O emissions relative to soils without ash due to adsorption of organic compounds, ammonium, and nitrate ions onto the charged surface of ash through hydrogen bonding. The ability of the ash to maintain higher soil pH during pineapple growth primarily contributed to low CO2 and N2O emissions. Co-application of pineapple residue ash and compound NPK fertilizer also improves soil ammonium and nitrate availability, and fruit quality of pineapples. Compound NPK fertilizers can be amended with pineapple residue ash to minimize CO2 and N2O emissions without reducing peat soil and pineapple productivity.

scholarly journals The influence of tillage on N<sub>2</sub>O fluxes from an intensively managed grazed grassland in Scotland

2016 ◽  
Author(s):  
N.J. Cowan ◽  
P.E. Levy ◽  
D. Famulari ◽  
M. Anderson ◽  
J. Drewer ◽  
...  
Keyword(s):  
Temperate Climate ◽  
N2o Emissions ◽  
Future Studies ◽  
Dynamic Chamber ◽  
Spatial Coverage ◽  
Before And After ◽  
Temporal And Spatial ◽  
N2o Fluxes ◽  
Intensively Managed ◽  
Measurement Period

Abstract. Intensively managed grass production in high rainfall temperate climate zones is a globally important source of N2O. Many of these grasslands are occasionally tilled and can lead to increased N2O emissions. This was investigated by comparing N2O fluxes from two adjacent intensively managed grazed grasslands in Scotland, one of which was tilled. A combination of eddy covariance, high resolution dynamic chamber and static chamber methods greatly improved the temporal and spatial coverage of N2O fluxes before and after the tillage event and is recommended to be followed in future studies. Total cumulative fluxes calculated for the tilled and un-tilled fields over the 175 day measurement period were 2.45 ± 0.27 and 2.08 ± 0.23 kg N2O-N ha−1, respectively. N2O emissions from the tilled field increased significantly for several days immediately after ploughing and remained elevated for approximately two months after the tillage event contributing to an estimated increase in N2O fluxes of 1.08 ± 0.14 kg N2O-N ha−1. Cumulative fluxes calculated over a 28 day period in August after the application of 70 kg-N ha−1 as ammonium nitrate to both fields were estimated at 0.42 ± 0.15 and 0.75 ± 0.14 kg N2O N ha−1 for the tilled and un-tilled fields, respectively. The tillage event appears to have substantially increased N2O fluxes from the tilled grassland field over a two month period; however, this increase may have been fractionally offset by a decrease in emissions after the August fertilisation event.

scholarly journals Gas chromatography and photoacoustic spectroscopy for the assessment of soil greenhouse gases emissions

2013 ◽  
Vol 43 (2) ◽  
pp. 262-269 ◽  
Author(s):  
Rodrigo da Silveira Nicoloso ◽  
Cimélio Bayer ◽  
Genuir Luis Denega ◽  
Paulo Armando Victória de Oliveira ◽  
Martha Mayumi Higarashi ◽  
...  
Keyword(s):  
Gas Chromatography ◽  
Greenhouse Gases ◽  
Photoacoustic Spectroscopy ◽  
Cropping Systems ◽  
Agricultural Practices ◽  
N2o Emissions ◽  
N2o Fluxes ◽  
Carbon Dioxide Co2 ◽  
Ghg Fluxes

Assessments of soil carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions are critical for determination of the agricultural practices' potential to mitigate global warming. This study evaluated the photoacoustic spectroscopy (PAS) for the assessment of soil greenhouse gases (GHG) fluxes in comparison to the standard gas chromatography (GC) method. Two long-term experiments with different tillage and cropping systems over a Paleudult were evaluated using static chambers. PAS measurements of CO2 and N2O concentrations showed good relationship and linearity (R2=0.98 and 0.94, respectively) with GC results. However, CH4 measurements were significantly affected by air sample moisture which interfered on CH4 detection by PAS. Overestimation of CO2 and N2O concentrations in air samples determined by PAS (14.6 and 18.7%, respectively) were also related to sampling moisture. CO2 and N2O fluxes showed good agreement between methods (R2=0.96 and 0.95, respectively), though PAS overestimated fluxes by 18.6 and 13.6% in relation to GC results, respectively. PAS showed good sensitivity and was able to detect CO2 and N2O fluxes as low as 332mg CO2 m-2 h-1 and 21µg N2O m-2 h-1. PAS analyzer should be detailed calibrated to reduce humidity interference on CO2, CH4 and N2O concentrations measurements avoiding overestimation or erroneous determination of soil GHG fluxes.

scholarly journals Combining two complementary micrometeorological methods to measure CH<sub>4</sub> and N<sub>2</sub>O fluxes over pasture

2015 ◽  
Vol 12 (18) ◽  
pp. 15245-15299 ◽  
Author(s):  
J. Laubach ◽  
M. Barthel ◽  
A. Fraser ◽  
J. E. Hunt ◽  
D. W. T. Griffith
Keyword(s):  
Large Fraction ◽  
Industrial Sector ◽  
N2o Emissions ◽  
Emission Rates ◽  
Co2 Fluxes ◽  
Nitrogen Inputs ◽  
Animal Excreta ◽  
N2o Fluxes ◽  
Ch4 And N2o ◽  
Carbon Dioxide Co2

Abstract. New Zealand's largest industrial sector is pastoral agriculture, giving rise to a large fraction of the country's emissions of methane (CH4) and nitrous oxide (N2O). We designed a system to continuously measure CH4 and N2O fluxes at the field scale on two adjacent pastures that differed with respect to management. At the core of this system was a closed-cell Fourier-transform infrared spectrometer (FTIR), measuring the mole fractions of CH4, N2O and carbon dioxide (CO2) at two heights at each site. In parallel, CO2 fluxes were measured using eddy-covariance instrumentation. We applied two different micrometeorological ratio methods to infer the CH4 and N2O fluxes from their respective mole fractions and the CO2 fluxes. The first is a variant of the flux-gradient method, where it is assumed that the turbulent diffusivities of CH4 and N2O equal that of CO2. This method was reliable when the CO2 mole-fraction difference between heights was at least 4 times greater than the FTIR's resolution of differences. For the second method, the temporal increases of mole fractions in the stable nocturnal boundary layer, which are correlated for concurrently-emitted gases, are used to infer the unknown fluxes of CH4 and N2O from the known flux of CO2. This method was sensitive to "contamination" from trace gas sources other than the pasture of interest and therefore required careful filtering. With both methods combined, estimates of mean daily CH4 and N2O fluxes were obtained for 60 % of days at one site and 77 % at the other. Both methods indicated both sites as net sources of CH4 and N2O. Mean emission rates for one year at the unfertilised, winter-grazed site were 8.2 (± 0.91) nmol CH4 m−2 s−1 and 0.40 (± 0.018) nmol N2O m−2 s−1. During the same year, mean emission rates at the irrigated, fertilised and rotationally-grazed site were 7.0 (± 0.89) nmol CH4 m−2 s−1 and 0.57 (± 0.019) nmol N2O m−2 s−1. At this site, the N2O emissions amounted to 1.19 (± 0.15) % of the nitrogen inputs from animal excreta and fertiliser application.

scholarly journals The effect of aggregates on N<sub>2</sub>O emission from denitrification in an agricultural peat soil

2011 ◽  
Vol 8 (2) ◽  
pp. 3253-3287 ◽  
Author(s):  
P. C. Stolk ◽  
R. F. A. Hendriks ◽  
C. M. J. Jacobs ◽  
E. J. Moors ◽  
P. Kabat
Keyword(s):  
Current Knowledge ◽  
Peat Soil ◽  
Model Performance ◽  
Biogeochemical Model ◽  
N2o Emissions ◽  
Model Combination ◽  
Model Concept ◽  
N2o Production ◽  
Structured Soils ◽  
N2o Fluxes

Abstract. Nitrous oxide (N2O) emissions are highly variable in time, with high peak emissions lasting as couple of days to weeks and low background emissions. This temporal variability is poorly understood which hampers the simulation of daily N2O emissions. In structured soils, like clay and peat, aggregates hamper the diffusion of oxygen, which leads to anaerobic microsites in the soil, favourable for denitrification. In this paper we studied the effect of aggregates in soils on the N2O emissions from denitrification. We presented a parameterization to simulate the effects of aggregates on N2O, following the mobile-immobile model concept. This parameterization was implemented in a field-scale hydrological-biogeochemical model combination. We compared the simulated fluxes with observed fluxes from a fertilized and drained peat soil with grass. The results of this study showed that aggregates strongly affect N2O emissions: peak emissions are lower, whereas the background emissions are slightly higher. Implementation of the effect of aggregates caused a decrease in the simulated annual emissions of more than 40%. The new parameterization also significantly improved the model performance to simulate observed N2O fluxes. Aggregates have more impact on the reduction of N2O than on the production of N2O. Reduction of N2O is more sensitive to changes in the drivers than production of N2O and is in that sense the key process to understand N2O emissions from denitrification. The effects of changing conditions on reduction of N2O relative to N2O production is dependent on the NO3 content of the soil. It is expected that in soils with a low NO3 content the influence of aggregates on the NO3 concentration is not negligible. This study showed that the current knowledge of the hydrological, biogeochemical and physical processes is sufficient to understand the observed N2O fluxes from a fertilized peatland. Further research is needed to test how aggregates affect the N2O fluxes in areas or periods with little NO3 in the soil.

scholarly journals Temporal and spatial variations of CO<sub>2</sub>, CH<sub>4</sub> and N<sub>2</sub>O fluxes at three differently managed grasslands

2013 ◽  
Vol 10 (2) ◽  
pp. 2635-2673 ◽  
Author(s):  
D. Imer ◽  
L. Merbold ◽  
W. Eugster ◽  
N. Buchmann
Keyword(s):  
Hot Spots ◽  
Environmental Drivers ◽  
Small Scale ◽  
N2o Emissions ◽  
Functional Relationships ◽  
Temporal And Spatial ◽  
N2o Fluxes ◽  
Intensively Managed ◽  
Ghg Fluxes ◽  
Management Effects

Abstract. A profound understanding of temporal and spatial variabilities of CO2, CH4 and N2O fluxes between terrestrial ecosystems and the atmosphere is needed to reliably quantify these fluxes and to develop future mitigation strategies. For managed grassland ecosystems, temporal and spatial variabilities of these three greenhouse gas (GHG) fluxes are due to environmental drivers as well as to fertilizer applications, grazing and cutting events. To assess how these affect GHG fluxes at Swiss grassland sites, we studied three sites along an altitudinal gradient that corresponds to a management gradient: from 400 m a.s.l. (intensively managed) to 1000 m a.s.l. (moderately intensive managed) to 2000 m a.s.l. (extensively managed). Temporal and spatial variabilities of GHG fluxes were quantified along small-scale transects of 16 static soil chambers at each site. We then established functional relationships between drivers and the observed fluxes on diel and annual time scales. Furthermore, spatial variabilities and their effect on representative site-specific mean chamber GHG fluxes were assessed using geostatistical semivariogram approaches. All three grasslands were N2O sources, with mean annual fluxes ranging from 0.15 to 1.28 nmol m−2 s−1. Contrastingly, all sites were net CH4 sinks, with uptake rates ranging from −0.56 to −0.15 nmol m−2 s−1. Mean annual respiration losses of CO2, as measured with opaque chambers, ranged from 5.2 to 6.5 μmol m−2 s−1. While the environmental drivers and their respective explanatory power for N2O emissions differed considerably among the three grasslands (adjusted r2 ranging from 0.19 to 0.42), CH4 and CO2 fluxes were much better constrained (adjusted r2 ranging from 0.41 to 0.83), in particular by soil water content and air temperature, respectively. Throughout the year, spatial heterogeneity was particularly high for N2O and CH4 fluxes. We found permanent hot spots for N2O emissions and CH4 uptake at the extensively managed site. Including these hot spots in calculating the mean chamber flux was essential to obtain a representative mean flux for this ecosystem. At the intensively managed grassland, management effects clearly dominated over effects of environmental drivers on N2O fluxes. For CO2 and CH4, the importance of management effects did depend on the status of the vegetation.

scholarly journals Greenhouse gas fluxes in a drained peatland forest during spring frost-thaw event

2009 ◽  
Vol 6 (3) ◽  
pp. 6111-6145 ◽  
Author(s):  
M. K. Pihlatie ◽  
R. Kiese ◽  
N. Brüggemann ◽  
K. Butterbach-Bahl ◽  
A.-J. Kieloaho ◽  
...  
Keyword(s):  
Peat Soil ◽  
Flux Measurement ◽  
Good Alternative ◽  
N2o Emission ◽  
Soil Parameters ◽  
N2o Emissions ◽  
N2o Production ◽  
Spring Frost ◽  
Carbon Dioxide Co2 ◽  
Ghg Fluxes

Abstract. Fluxes of greenhouse gases (GHG) carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) were measured during a two month campaign at a drained peatland forest in Finland by the eddy covariance (EC) technique (CO2 and N2O), and automatic and manual chambers (CO2, CH4 and N2O). In addition, GHG concentrations and soil parameters (mineral nitrogen, temperature, moisture content) in the peat profile were measured. The aim of the measurement campaign was to quantify the GHG fluxes before, during and after thawing of the peat soil, a time period with potentially high GHG fluxes, and to compare different flux measurement methods. The forest was a net CO2 sink during the two months and the fluxes of CO2 dominated the GHG exchange. The peat soil was a small sink of atmospheric CH4 but a small source of N2O. Both CH4 oxidation and N2O production took place in the top-soil whereas CH4 was produced in the deeper layers of the peat. During the thawing of the peat distinct peaks in CO2 and N2O emissions were observed. The CO2 peak followed tightly the increase in soil temperature, whereas the N2O peak occurred with an approx. one week delay after soil thawing. CH4 fluxes did not respond to the thawing of the peat soil. The CO2 and N2O emission peaks were not captured by the manual chambers and hence we conclude that automatic chamber measurements or EC are necessary to quantify fluxes during peak emission periods. Sub-canopy EC measurements and chamber-based fluxes of CO2 and N2O were comparable, although the fluxes of N2O measured by EC were close to the detection limit of the EC system. We conclude that if fluxes are high enough, i.e. greater than 5–10 μg N m−2 h−1, the EC method is a good alternative to measure N2O and CO2 fluxes at ecosystem scale, thereby minimizing problems with chamber enclosures and spatial representativeness of the measurements.

scholarly journals Nitrous oxide emissions from managed grassland: a comparison of eddy covariance and static chamber measurements

2011 ◽  
Vol 4 (10) ◽  
pp. 2179-2194 ◽  
Author(s):  
S. K. Jones ◽  
D. Famulari ◽  
C. F. Di Marco ◽  
E. Nemitz ◽  
U. M. Skiba ◽  
...  
Keyword(s):  
Detection Limit ◽  
Eddy Covariance ◽  
Sonic Anemometer ◽  
Tunable Diode Laser ◽  
Nitrous Oxide Emissions ◽  
N2o Emissions ◽  
Small Contribution ◽  
Mineral N ◽  
N2o Fluxes ◽  
Chamber Measurements

Abstract. Managed grasslands are known to be an important source of N2O with estimated global losses of 2.5 Tg N2O-N yr−1. Chambers are to date the most widely used method to measure N2O fluxes, but also micrometeorological methods are successfully applied. In this paper we present a comparison of N2O fluxes measured by non-steady state chambers and eddy covariance (EC) (using an ultra-sonic anemometer coupled with a tunable diode laser) from an intensively grazed and fertilised grassland site in South East Scotland. The measurements were taken after fertilisation events in 2003, 2007 and 2008. In four out of six comparison periods, a short-lived increase of N2O emissions was observed after mineral N application, returning to background level within 2–6 days. Highest fluxes were measured by both methods in July 2007 with maximum values of 1438 ng N2O-N m−2 s−1 (EC) and 651 ng N2O-N m−2 s−1 (chamber method). Negative fluxes above the detection limit were observed in all comparison periods by EC, while with chambers, the recorded negative fluxes were always below detection limit. Median and average fluxes over each period were always positive. Over all 6 comparison periods, 69% of N2O fluxes measured by EC at the time of chamber closure were within the range of the chamber measurements. N2O fluxes measured by EC during the time of chamber closure were not consistently smaller, neither larger, compared to those measured by chambers: this reflects the fact that the different techniques integrate fluxes over different spatial and temporal scales. Large fluxes measured by chambers may be representing local hotspots providing a small contribution to the flux measured by the EC method which integrates over a larger area. The spatial variability from chamber measurements was high, as shown by a coefficient of variation of up to 139%. No diurnal pattern of N2O fluxes was observed, possibly due to the small diurnal variations of soil temperature. The calculation of cumulative fluxes using different integration methods showed EC data provide generally lower estimates of N2O emissions than chambers.

scholarly journals Temporal and spatial variations of soil CO<sub>2</sub>, CH<sub>4</sub> and N<sub>2</sub>O fluxes at three differently managed grasslands

2013 ◽  
Vol 10 (9) ◽  
pp. 5931-5945 ◽  
Author(s):  
D. Imer ◽  
L. Merbold ◽  
W. Eugster ◽  
N. Buchmann
Keyword(s):  
Hot Spots ◽  
Explanatory Power ◽  
Environmental Drivers ◽  
N2o Emissions ◽  
Uptake Rates ◽  
Temporal And Spatial ◽  
N2o Fluxes ◽  
Intensively Managed ◽  
Ghg Fluxes ◽  
Management Effects

Abstract. A profound understanding of temporal and spatial variabilities of soil carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes between terrestrial ecosystems and the atmosphere is needed to reliably quantify these fluxes and to develop future mitigation strategies. For managed grassland ecosystems, temporal and spatial variabilities of these three soil greenhouse gas (GHG) fluxes occur due to changes in environmental drivers as well as fertilizer applications, harvests and grazing. To assess how such changes affect soil GHG fluxes at Swiss grassland sites, we studied three sites along an altitudinal gradient that corresponds to a management gradient: from 400 m a.s.l. (intensively managed) to 1000 m a.s.l. (moderately intensive managed) to 2000 m a.s.l. (extensively managed). The alpine grassland was included to study both effects of extensive management on CH4 and N2O fluxes and the different climate regime occurring at this altitude. Temporal and spatial variabilities of soil GHG fluxes and environmental drivers on various timescales were determined along transects of 16 static soil chambers at each site. All three grasslands were N2O sources, with mean annual soil fluxes ranging from 0.15 to 1.28 nmol m−2 s−1. Contrastingly, all sites were weak CH4 sinks, with soil uptake rates ranging from −0.56 to −0.15 nmol m−2 s−1. Mean annual soil and plant respiration losses of CO2, measured with opaque chambers, ranged from 5.2 to 6.5 μmol m−2 s−1. While the environmental drivers and their respective explanatory power for soil N2O emissions differed considerably among the three grasslands (adjusted r2 ranging from 0.19 to 0.42), CH4 and CO2 soil fluxes were much better constrained (adjusted r2 ranging from 0.46 to 0.80) by soil water content and air temperature, respectively. Throughout the year, spatial heterogeneity was particularly high for soil N2O and CH4 fluxes. We found permanent hot spots for soil N2O emissions as well as locations of permanently lower soil CH4 uptake rates at the extensively managed alpine site. Including hot spots was essential to obtain a representative mean soil flux for the respective ecosystem. At the intensively managed grassland, management effects clearly dominated over effects of environmental drivers on soil N2O fluxes. For CO2 and CH4, the importance of management effects did depend on the status of the vegetation (LAI).

scholarly journals Combining two complementary micrometeorological methods to measure CH<sub>4</sub> and N<sub>2</sub>O fluxes over pasture

2016 ◽  
Vol 13 (4) ◽  
pp. 1309-1327 ◽  
Author(s):  
Johannes Laubach ◽  
Matti Barthel ◽  
Anitra Fraser ◽  
John E. Hunt ◽  
David W. T. Griffith
Keyword(s):  
Large Fraction ◽  
Industrial Sector ◽  
N2o Emissions ◽  
Emission Rates ◽  
Co2 Fluxes ◽  
Nitrogen Inputs ◽  
Animal Excreta ◽  
N2o Fluxes ◽  
Ch4 And N2o ◽  
Carbon Dioxide Co2

Abstract. New Zealand's largest industrial sector is pastoral agriculture, giving rise to a large fraction of the country's emissions of methane (CH4) and nitrous oxide (N2O). We designed a system to continuously measure CH4 and N2O fluxes at the field scale on two adjacent pastures that differed with respect to management. At the core of this system was a closed-cell Fourier transform infrared (FTIR) spectrometer, which measured the mole fractions of CH4, N2O and carbon dioxide (CO2) at two heights at each site. In parallel, CO2 fluxes were measured using eddy-covariance instrumentation. We applied two different micrometeorological ratio methods to infer the CH4 and N2O fluxes from their respective mole fractions and the CO2 fluxes. The first is a variant of the flux-gradient method, where it is assumed that the turbulent diffusivities of CH4 and N2O equal that of CO2. This method was reliable when the CO2 mole-fraction difference between heights was at least 4 times greater than the FTIR's resolution of differences. For the second method, the temporal increases of mole fractions in the stable nocturnal boundary layer, which are correlated for concurrently emitted gases, are used to infer the unknown fluxes of CH4 and N2O from the known flux of CO2. This method was sensitive to “contamination” from trace gas sources other than the pasture of interest and therefore required careful filtering. With both methods combined, estimates of mean daily CH4 and N2O fluxes were obtained for 56 % of days at one site and 73 % at the other. Both methods indicated both sites as net sources of CH4 and N2O. Mean emission rates for 1 year at the unfertilised, winter-grazed site were 8.9 (±0.79) nmol CH4 m−2 s−1 and 0.38 (±0.018) nmol N2O m−2 s−1. During the same year, mean emission rates at the irrigated, fertilised and rotationally grazed site were 8.9 (±0.79) nmol CH4 m−2 s−1 and 0.58 (±0.020) nmol N2O m−2 s−1. At this site, the N2O emissions amounted to 1.21 (±0.15) % of the nitrogen inputs from animal excreta and fertiliser application.

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