Nitrous oxide emission factors from an intensively grazed temperate grassland: a comparison of cumulative emissions determined by eddy covariance and static chamber methods

Murphy, Rachael M.; Saunders, Matthew; Richards, Karl G.; Krol, Dominika J.; Gebremichael, Amanuel W.; Rambaud, James; Cowan, Nicholas; Lanigan, Gary J.. 2022 Nitrous oxide emission factors from an intensively grazed temperate grassland: a comparison of cumulative emissions determined by eddy covariance and static chamber methods. Agriculture, Ecosystems and Environment, 324, 107725. 11, pp. https://doi.org/10.1016/j.agee.2021.107725

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Official URL: http://dx.doi.org/10.1016/j.agee.2021.107725

Abstract/Summary

Quantifying nitrous oxide (N2O) emissions from grazed pastures can be problematic due to the presence of hotspots and hot moments of N2O from animal excreta and synthetic fertilisers. In this study, we quantified field scale N2O emissions from a temperate grassland under a rotational grazing management using eddy covariance (EC) and static chamber techniques. Measurements of N2O by static chambers were made for four out of nine grazing events for a control, calcium ammonium nitrate (CAN), synthetic urine (SU) + CAN and dung + CAN treatments. Static chamber N2O flux measurements were upscaled to the field scale (FCH FIELD) using site specific emission factors (EF) for CAN, SU+CAN and dung + CAN. Mean N2O EFs were greatest from the CAN treatment while dung + CAN and SU + CAN emitted similar N2O-N emissions. Cumulative N2O-N emissions over the study period measured by FCH FIELD measurements were lower than gap-filled EC measurements. Emission factors of N2O from grazing calculated by FCH FIELD and gap-filled were 0.72% and 0.96%, respectively. N2O-N emissions were derived mainly from animal excreta (dung and urine) contributing 50% while N2O-N losses from CAN and background accounted for 36% and 14%, respectively. The study highlights the advantage of using both the EC and static chamber techniques in tandem to better quantify both total N2O-N losses from grazed pastures while also constraining the contribution of individual N sources. The EC technique was most accurate in quantifying N2O emissions, showing a range of uncertainty that was seven times lower relative to that attributed to static chamber measurements, due to the small chamber sample size per treatment and highly variable N2O flux measurements over space and time.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1016/j.agee.2021.107725
UKCEH and CEH Sections/Science Areas:	Atmospheric Chemistry and Effects (Science Area 2017-)
ISSN:	0167-8809
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
Additional Keywords:	grasslands, eddy covariance, grazing, nitrous oxide, emission factors
NORA Subject Terms:	Agriculture and Soil Science Atmospheric Sciences
Date made live:	01 Dec 2021 15:01 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/531488

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1016/j.agee.2021.107725

UKCEH and CEH Sections/Science Areas:

Atmospheric Chemistry and Effects (Science Area 2017-)

ISSN:

0167-8809

Additional Information. Not used in RCUK Gateway to Research.:

Open Access paper - full text available via Official URL link.

Additional Keywords:

grasslands, eddy covariance, grazing, nitrous oxide, emission factors