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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 & Environment ( IF 6.0 ) Pub Date : 2021-10-25 , DOI: 10.1016/j.agee.2021.107725
Rachael M. Murphy 1, 2 , Matthew Saunders 1 , Karl G. Richards 2 , Dominika J. Krol 2 , Amanuel W. Gebremichael 2 , James Rambaud 2 , Nicholas Cowan 3 , Gary J. Lanigan 2
Affiliation  

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.



中文翻译:

来自密集放牧温带草原的一氧化二氮排放因子:由涡流协方差和静态室方法确定的累积排放量的比较

由于动物排泄物和合成肥料中存在热点和 N 2 O的热点,因此量化放牧牧场的一氧化二氮 (N 2 O) 排放量可能存在问题。在这项研究中,我们使用涡流协方差 (EC) 和静态室技术量化了轮牧管理下温带草原的田间规模 N 2 O 排放。对于对照、硝酸铵钙 (CAN)、合成尿 (SU) + CAN 和粪便 + CAN 处理的九个放牧事件中的四个,通过静态室测量 N 2 O。静态室 N 2 O 通量测量被放大到现场规模(F CH FIELD) 使用针对 CAN、SU+CAN 和粪便 + CAN 的现场特定排放因子 (EF)。CAN 处理的平均 N 2 O EF 最大,而粪便 + CAN 和 SU + CAN 排放的 N 2 O-N 排放量相似。通过 F CH FIELD测量值测量的研究期间的累积 N 2 O-N 排放量低于间隙填充 EC 测量值。F CH FIELD和gap-filled计算的放牧N 2 O排放因子分别为0.72%和0.96%。N 2 O-N 排放主要来自动物排泄物(粪便和尿液),占 50%,而 N 2来自 CAN 和背景的 ON 损失分别占 36% 和 14%。该研究强调了同时使用 EC 和静态室技术的优势,以更好地量化放牧牧场的N 2 O-N总损失,同时限制单个 N 源的贡献。EC 技术在量化 N 2 O 排放量方面最为准确,显示的不确定性范围比静态室测量低 7 倍,这是由于每次处理的室样本量小,且 N 2 O 通量测量结果变化很大空间和时间。

更新日期:2021-10-26
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