Upscaling chamber-based measurements of N₂O emissions at snowmelt

Abstract

I. 2005. Upscaling chamber-based measurements of N 2 O emissions at snowmelt. Can. J. Soil Sci. 85: 113-125. One impediment to accurate national estimation of N 2 O is the difficulty in upscaling N 2 O measurements made at discrete points to larger field and regional scales. Our objective was to estimate N 2 O emissions during snowmelt in 2002 for a township (approximately 92 km 2 ) near Laird, Saskatchewan. Chamber measurements were made at 12 sites in the township: four fields with canola (Brassica napus L.) residues, four with pea (Pisum sativum L.) residues, three with wheat (Triticum aestivum L.) residues, and one field that received cattle manure. Ten sampling chambers were used at each site, and N 2 O samples were made on 7 d during the snowmelt period (from 2002 Apr. 03 to Apr. 17). Cumulative N 2 O emissions during the 14 days of the snowmelt period differed between crop residue types: cumulative emissions from sites with wheat residues were 105.6 g N 2 O-N ha -1 and were significantly higher (P < 0.1) than those from fields with pea and canola residues (79.6 and 75.2 g N 2 O-N ha -1 respectively). The single manured site assessed had the highest cumulative emissions of 330.7 g N 2 O-N ha -1 . The crop-specific emissions from the chamber-based measurements were multiplied by the area of each crop type in the township to calculate an area-weighted value for emissions. Cumulative emissions were 93.4 g N 2 O-N ha -1 for the chamber-based measurements. Water-filled pore space and soil temperature were not significantly correlated with cumulative emissions. Cumulative emissions from sites with fall nitrate levels below 8.0 kg ha -1 were consistently lower than those above this threshold. The emissions for the Laird township were well below the emissions calculated for most other studies in the Prairies and in central Canada. The lower emissions were probably due to low soil water contents and soil nitrate levels in the fall of 2001 and belownormal snowfall in the winter of [2001][2002]. This reinforces the importance in antecedent moisture conditions and soil N levels for modeling of emissions at snowmelt. For personal use only.

Micrometeorological Measurements Reveal Large Nitrous Oxide Losses during Spring Thaw in Alberta

“…At cropping sites in central Alberta, Nyborg et al [8] found exceptionally large spring losses (16.3 kg N 2 O-N ha −1 ), but at a nearby location Lemke et al [6,9] and Izaurralde et al [10] found much smaller losses (0.04 to 1.81 kg N 2 O-N ha −1 ). Corre et al [11], Pennock and Corre [12], and Pennock et al [13] found small losses from sites in the neighboring province of Saskatchewan (0.047 to 0.53 kg N 2 O-N ha −1 ). The current regional perspective is that spring N 2 O emissions in western Canada are smaller than in eastern Canada [9], which contributes to low annual N 2 O emissions from western Canada [14].…”

Towards optimum sampling for regional-scale N2O emission monitoring in Canada

“…Sample size is also constrained by available resources. Several studies (Williams et al 1999;Corre et al 1996Corre et al , 1999Pennock et al 2005) have used between 8 and 10 individual measurements per site/strata over their field studies, a number that was clearly manageable for the resources available for their studies. Ideally, more rigorous analyses of the appropriate number of samples for different designs will emerge in the near future but a sample size of 8 to 10 for each strata in regional-scale studies has been successfully used to date.…”

“…For example, the NCGAVS framework defines management systems broadly enough that only a limited number (e.g., 3 to 10) of land use/management combinations will occur within a given study region (Table 1). Fieldspecific differences in management history can create a range of controlling conditions and emission responses within a given land use/management combination (Pennock et al 2005). These spatial differences, coupled with the different crop rotation phases, ideally require that multiple fields (i.e., 3 to 5) be sampled within a given land use/management combination.…”

Testing and evaluation of a new airborne system for continuous N&lt;sub&gt;2&lt;/sub&gt;O, CO&lt;sub&gt;2&lt;/sub&gt;, CO, and H&lt;sub&gt;2&lt;/sub&gt;O measurements: the Frequent Calibration High-performance Airborne Observation System (FCHAOS)

“…These observations have proven particularly valuable for quantifying emissions from individual, large emitting point sources (Conley et al, 2017;Mehrotra et al, 2017) as well as constraining emissions of highly heterogeneous processes on 10-100 km scales (Karion et al, 2015;Peischl et al, 2015;Smith et al, 2015;Kort et al, 2016). Continuous, 1 Hz airborne sampling of N 2 O with high accuracy and precision has proven more elusive, with limited aircraft campaigns reporting continuous airborne N 2 O (Kort et al, 2011;Wofsy, 2011;Xiang et al, 2013), systems being large and challenging to operate with frequent attention to supplies of cryogens (Santoni et al, 2014), and newer systems showing large cabin pressure dependencies (Pitt et al, 2016).…”