Estimates of nitrous oxide emissions from agricultural fields over 28 months

Abstract

Field studies conducted throughout the calendar year are needed to improve flux estimates for the greenhouse gas nitrous oxide (N2O). In this study, we report monthly N2O emissions measured using micrometeorological techniques and a Tunable Diode Laser Trace Gas Analyzer (TDLTGA). Nitrous oxide fluxes were measured at the Elora Research Station (20 km north of Guelph, Ontario) from July to November 1992, and from March 1993 to February 1995, giving a total of 2445 daily averages obtained during the full length of the experiment. The soil at the experimental site was a Conestogo silt loam (Gleyed melanic brunisol). Several fields were monitored including fallow, manured fallow, Kentucky bluegrass, alfalfa, barley, canola, soybeans and corn plots. Spring thaw emissions from fallow or ploughed plots measured from March to April ranged from 1.5 to 4.3 kg N ha−1, corresponding to approximately 65% of the total annual emission. Similar effects were not observed on the vegetated (alfalfa and grass) plots. The lowest total annual N2O emissions were measured for second year alfalfa (1 kg N ha−1 yr−1) and bluegrass (0 to 0.5 kg N ha−1 yr−1). Higher annual emissions (2.5 to 4.0 kg N ha−1 yr−1) were observed for corn, barley, canola, and fallow plots. Highest annual emissions were measured after addition of nitrogen in the form of animal manure on a fallowed plot (5.7 to 7.4 kg N ha−1 yr−1), and alfalfa residue by fall-ploughing (6.1 kg N ha−1 yr−1). Plot management during the previous year affected N2O emissions, particularly on the soybean plot (5.9 kg N ha−1 yr−1) that followed a manured fallow treatment. The micrometeorological technique used in this study was successful at quasi-continuous monitoring of N2O fluxes from several plots, and therefore, useful for detecting long-term effects of management on emissions. Key words: Nitrous oxide, N2O fluxes, trace gases, agriculture, greenhouse gases

Upscaling chamber-based measurements of N2O emissions at snowmelt

“…For example, Wagner-Riddle et al (1997) observed cumulative spring emissions of between 1.46 and 4.34 kg N 2 O-N ha -1 from their fallow and cropped plots. Even if the fluxes observed at Laird are extrapolated over a longer time period they do not come close to the emissions observed in the Wagner-Riddle et al (1997) study.…”

“…For example, Wagner-Riddle et al (1997) observed cumulative spring emissions of between 1.46 and 4.34 kg N 2 O-N ha -1 from their fallow and cropped plots. Even if the fluxes observed at Laird are extrapolated over a longer time period they do not come close to the emissions observed in the Wagner-Riddle et al (1997) study. Van Bochove et al (2000) detected order-of-magnitude differences between years (i.e., 0.4 to 10 kg N 2 O-N ha -1 ), which they attributed primarily to differences in the soil moisture conditions in the preceding year and to the timing, depth, and physical attributes of the snowpack.…”

“…Temporal extrapolation is not required if continuous measurement of emissions during snowmelt can be made. Micrometeorological flux measurements offer the closest approximation to this, and quasi-continuous micrometeorological studies such as Wagner-Riddle et al (1997) and Grant and Pattey (1999) provide essential, highly resolved data on emissions. These systems also provide a spatially integrated measurement of up to field-scale areas (depending on the height of the instrument).…”

Potential N2O emissions from leguminous tree plantation soils in the humid tropics

“…Thus plant residues of leguminous species with high nitrogen concentrations would increase nitrogen availability in soils, resulting in increased N 2 O emission rates. For example, N 2 O flux at a site where wheat was cultivated with a leguminous crop was greater than that at a wheat monoculture site [Nishimura et al, 2005;Wagner-Riddle et al, 1997]. Because large amounts of nitrogen are continuously supplied to soils through plant litterfall, leguminous plantations raise nitrogen availability in the soil, making these plantations a possible N 2 O source [Intergovernmental Panel on Climate Change (IPCC), 2003].…”

Management of Canadian prairie region grazed grasslands: Soil C sequestration, livestock productivity and profitability

“…More research is needed to determine the most cost-effective method of seeding alfalfa and other legumes into improved tame pastures, including no-till methods such as frost seeding, feeding of the seed to cattle, or seed drilling with a notill drill. Indications of reductions in methane emissions from cattle on grass/legume pastures compared to cattle on pure grass stands (McCaughey et al 1997) or when finished in feedlots (Cohen et al 2004), and evidence of lower N 2 O emissions from legume stands than from N fertilized systems (Wagner-Riddle et al 1997), provide additional justification for such efforts.…”