Agricultural systems are known to emit nitrous oxide (N2O) – a potent greenhouse gas in a temporally and spatially discontinuous fashion. A roving micrometeorological tower flux measurement system, designed to quantify greenhouse gas (GHG) emissions from agricultural fields, was used to make continuous measurements of N2O fluxes. Flux measurements were carried out year round in 2003-04 in an edible pea field in Western Quebec and in 2004-05 in an alfalfa-timothy forage field in Eastern Ontario. Both fields belonged to private producers and received either solid or liquid dairy manure. The experiment was designed to capture the expected large emissions occurring as a result of field management activities or following large precipitation events. This study was also aimed at quantifying important winter and spring snowmelt emissions. The above measurements were used to verify the performance of the simulation model DNDC (DeNitrification-DeComposition; Li et al., 1992) in estimating N2O emissions from legumes in response to dairy manure fertilization. Estimates of N2O emissions were made for a range of precipitation and temperature conditions by using the climate data from the five previous years (1998-2002) to drive the model. Sensitivity tests were also carried out in which the timing and amount of fertilizer applied was varied. The selected management options were kept within the guidelines for timing and amount of fertilizer application based on Ontario and Quebec regulations. The results of this study will be used for verifying the performance of version 8.6H of DNDC to simulate N2O emissions from legume fields and for evaluating the impact of climatic and management conditions on the calculated IPCC N2O emission factors. Results will provide a better understanding of the typical emissions in the region and address potential modifications to IPCC methodologies.
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