Ammonia emission measurements of an intensively grazed pasture

Voglmeier, Karl; Jocher, Markus; Häni, Christoph; Ammann, Christof

doi:10.5194/bg-2018-86

Cited by 4 publications

(6 citation statements)

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“…The experiment was conducted at the research farm Agroscope Posieux in the Pre-Alps of Switzerland in the canton of Fribourg (46°46´04´´N, 7°06´28´´E) and has been already described in detail in Voglmeier et al (2018). The farm is located at an elevation of 642 m with an annual average temperature of 8.7 °C and an annual average rain amount of 1075 mm (MeteoSwiss, 2018).…”

Section: Experimental Sitementioning

confidence: 99%

“…Because N excretion cannot easily be measured in the field, we estimated it with a Swiss dairy cow nitrogen budget model. In short, this model balances the N flows in the cow by using measured daily/seasonal N in the feed input, storage in body weight gain and milk to give an output of daily values of urine and dung N. For further details see explanation in Voglmeier et al (2018) who also estimated the corresponding uncertainty of the total N and urine / dung N to be 15 % (2σ) for the same experiment. Seasonal statistics of the input variables are given in Table 2.…”

Section: N Input To the Pasturementioning

confidence: 99%

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Grazing related nitrous oxide emissions: from patch scale to field scale

Voglmeier¹,

Six²,

Jocher³

et al. 2018

Preprint

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Abstract. Grazed pastures are strong sources of the greenhouse gas nitrous oxide (N2O). The quantification of the emissions is challenging due to the strong spatial and temporal variability of the emission sources and therefore emission estimates are very uncertain. This study presents N2O emission measurements of two grazing systems in western Switzerland over the grazing season 2016. Two herds of dairy cows were kept in an intensive rotational grazing management. The diet for the cows consisted of different protein to energy ratios resulting in different N excretion rates. The N in the excretion was estimated by an animal budget model taking into account the measurements of feed intake, milk yield and body weight of the cow herds. Excreta patches and background surfaces on the pasture were identified manually after different grazing rotations and the magnitude and temporal pattern of the single emission sources were measured with a Fast-box (FB) chamber. The field scale fluxes were quantified using two eddy covariance (EC) systems. The FB measurements were finally up-scaled to the field and compared to the EC measurements for quality control by using EC footprint estimates of a backward Lagrangian stochastic dispersion model. Neglecting emission periods influenced by fertilizer applications resulted in significant higher system emissions (960 &#177; 219&#8201;g&#8201;N2O-N, or 25&#8201;%) for the full grazing regime (system G) compared to the system with the N balanced diet (system M). Relating the found emissions to the excreta N resulted in grazing related EFs of 1.24 &#177; 0.20&#8201;% for system M and 1.36 &#177; 0.26&#8201;% for system G. The found grazing related EFs were thus significantly smaller compared to the EF of 2&#8201;% of the IPCC guidelines. Disaggregating the up-scaled fluxes into single contributors showed that urine patch emission dominated the field scale fluxes (57&#8201;%), followed by significant background emissions (38&#8201;%) and only a small contribution of dung patch emission (5&#8201;%). The resulting EFs of 1.13 &#177; 0.3&#8201;% and 0.17 &#177; 0.04&#8201;% for urine and dung indicates the need to disaggregate the grazing related EFs by excreta type. The study also highlights the advantage of an N optimised diet which resulted in reduced N2O emissions on the system level.

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Section: Experimental Sitementioning

confidence: 99%

Section: N Input To the Pasturementioning

confidence: 99%

Grazing related nitrous oxide emissions: from patch scale to field scale

Voglmeier¹,

Six²,

Jocher³

et al. 2018

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…The experiment was conducted at the research farm Agroscope Posieux in the Prealps of Switzerland in the canton of Fribourg (46 • 46 04 N, 7 • 06 28 E) during the grazing season of 2016 and has already been described in detail by Voglmeier et al (2018). The farm is located at an elevation of 642 m with an annual average temperature of 8.7 • C and a mean annual precipitation sum of 1075 mm (MeteoSwiss, 2018).…”

Section: Experimental Sitementioning

confidence: 99%

“…The breakdown of the excreted N in urine and dung was based on work by Bracher et al (2011). For further details see Voglmeier et al (2018), where the corresponding uncertainty of the total N and urine/dung N was estimated to be 15 % (2σ ) for the same experiment. Seasonal statistics of the input variables are given in Table 2.…”

Section: N Input To the Pasturementioning

confidence: 99%

review of "Grazing related nitrous oxide emissions: from patch scale to field scale"

Anonymous

2018

Preprint

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Grazed pastures are strong sources of the greenhouse gas nitrous oxide (N 2 O). The quantification of N 2 O emissions is challenging due to the strong spatial and temporal variabilities of the emission sources and so N 2 O emission estimates are very uncertain. This study presents N 2 O emission measurements from two grazing systems in western Switzerland over the grazing season of 2016. The 12 dairy cows of each herd were kept in an intensive rotational grazing management. The diet for the two herds of cows consisted of different protein-to-energy ratios (system G: grass only diet; system M: grass with additional maize silage) resulting in different nitrogen (N) excretion rates. The N in the excretion was estimated by calculating the animal nitrogen budget taking into account the measurements of feed intake, milk yield, and body weight of the cow herds. Directly after the rotational grazing phases, background and urine patches were identified based on soil electric conductivity measurements while fresh dung patches were identified visually. The magnitude and temporal pattern of these different emission sources were measured with a fast-box (FB) chamber and the field-scale fluxes were quantified using two eddy covariance (EC) systems. The FB measurements were finally upscaled to the field level and compared to the EC measurements for quality control by using EC footprint estimates of a backward Lagrangian stochastic dispersion model. The comparison between the two grazing systems was performed during emission periods that were not influenced by fertilizer applications. This allowed the calculation of the excreta-related N 2 O emissions per cow and grazing hour and resulted in considerably higher emissions for system G compared to system M. Relating the found emissions to the excreta N resulted in excreta-related emission factors (EFs) of 0.74 ± 0.26 % for system M and 0.83 ± 0.29 % for system G. These EF values were thus significantly smaller compared to the default EF of 2 % provided by the IPCC guidelines for cattle excreta deposited on pasture. The measurements showed that urine patch emission dominated the field-scale fluxes (57 %), followed by significant background emissions (38 %), and only a small contribution of dung patch emission (5 %). The resulting source-specific EFs exhibited a clear difference between urine (1.12 ± 0.43 %) and dung (0.16 ± 0.06 %), supporting a disaggregation of the grazing-related EFs by excreta type in emission inventories. The study also highlights the advantage of a N-optimized diet, which resulted in reduced N 2 O emissions from animal excreta.

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“…Data availability. Data obtained in this study are available online at https://doi.org/10.5281/zenodo.1305180 (Voglmeier et al, 2018).…”

mentioning

confidence: 99%

Ammonia emission measurements of an intensively grazed pasture

Voglmeier

Jocher

Häni³

et al. 2018

Biogeosciences

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Abstract. The quantification of ammonia (NH3) emissions is still a challenge and the corresponding emission factor for grazed pastures is uncertain. This study presents NH3 emission measurements of two pasture systems in western Switzerland over the entire grazing season 2016. During the measurement campaign, each pasture system was grazed by 12 dairy cows in an intensive rotational management. The cow herds on the two pastures differed in the energy to protein balance of the diet. NH3 concentrations were measured upwind and downwind of a grazed subplot with line-integrating open path instruments that were able to retrieve small horizontal concentration differences (< 0.2 µg NH3 m−3). The NH3 emission fluxes were calculated by applying a backward Lagrangian stochastic (bLS) dispersion model to the difference of paired concentration measurements and ranged from 0 to 2.5 µg N–NH3 m−2 s−1. The fluxes increased steadily during a grazing interval from previous non-significant values to reach maximum emissions at the end of the grazing interval. Afterwards they decreased exponentially to near zero-values within 3–5 days. A default emission curve was calculated for each of the two systems and adopted to each rotation in order to account for missing data values and to estimate inflow disturbances due to grazing on upwind paddocks. Dung and cow location were monitored to account for the non-negligible inhomogeneity of cow excreta on the pasture. The average emission (± SD of individual rotation values) per grazing hour was calculated as 0.64±0.11 g N–NH3 cow−1 h−1 for the herd with the N-balanced diet (system M) and 1.07±0.06 g N–NH3 cow−1 h−1 for the herd with the protein-rich grass-only diet (system G). Surveys of feed intake, body weight and milk yield of the cow herds were used to estimate the nitrogen (N) excretion by an animal N budget model. Based on that, mean relative emission factors of 6.4±2.0 % and 8.7±2.7 % of the applied urine N were found for the systems M and G, respectively. The results can be used to validate the Swiss national emission inventory and demonstrate the positive effect of an N-balanced diet on pasture NH3 emissions.

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Ammonia emission measurements of an intensively grazed pasture

Cited by 4 publications

References 1 publication

Grazing related nitrous oxide emissions: from patch scale to field scale

Grazing related nitrous oxide emissions: from patch scale to field scale

review of "Grazing related nitrous oxide emissions: from patch scale to field scale"

Ammonia emission measurements of an intensively grazed pasture

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Ammonia emission measurements of an intensively grazed pasture

Cited by 4 publications

References 1 publication

Grazing related nitrous oxide emissions: from patch scale to field scale

Grazing related nitrous oxide emissions: from patch scale to field scale

review of &quot;Grazing related nitrous oxide emissions: from patch scale to field scale&quot;

Ammonia emission measurements of an intensively grazed pasture

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review of "Grazing related nitrous oxide emissions: from patch scale to field scale"