Estimation of N 2 O emissions from agricultural soils in Canada. II. 1990–2005 inventory
2008; Canadian Science Publishing; Volume: 88; Issue: 5 Linguagem: Inglês
10.4141/cjss07026
ISSN1918-1841
AutoresPhilippe Rochette, Devon E. Worth, E.C. Huffman, James A. Brierley, B.G. McConkey, Jingyi Yang, J J Hutchinson, R. L. Desjardins, R.E. Lemke, S. Gameda,
Tópico(s)Soil and Water Nutrient Dynamics
ResumoInternational initiatives such as the United Nations Framework Convention on Climate Change and the Kyoto Protocol require that countries conduct national inventories of their greenhouse gas emissions. The primary objective of the present study was to apply a country-specific (Tier II) methodology at the regional (≈150 000 ha) scale to estimate direct N 2 O emissions from agricultural soils in Canada for the period 1990–2005. Other N 2 O sources such as manure management and indirect emissions were estimated using the Tier I Intergovernmental Panel on Climate Change (IPCC) methodology and were included to provide a complete assessment of agricultural N 2 O emissions. Total N 2 O emissions from agricultural sources averaged 58.1 Gg N 2 O-N yr -1 between 1990 and 2005 (from 48.9 in 1990 to 71.6 Gg N 2 O-N yr -1 in 2004). Of these mean emissions, 39.3 Gg N 2 O-N yr -1 or 68% were direct emissions from soils, 8.7 Gg N 2 O-N yr -1 or 15% were direct emissions from animal waste management systems and 10.1 Gg N 2 O-N yr -1 or 17% were from indirect emissions. Application of synthetic N fertilizers was the largest direct source of soil N 2 O with average emissions during the inventory period of 13.7 Gg N 2 O-N yr -1 or 35% of direct emissions. Crop residues (9.3 Gg N 2 O-N yr -1 ; 24%), grazing animals (6.8 Gg N 2 O-N yr -1 ; 17%) and manure applied to soils (4.1 Gg N 2 O-N yr -1 ; 10%) were the other major direct soil N 2 O sources. New non-IPCC N 2 O sources/offsets included in the Tier II methodology accounted for 10% of total direct soil emissions. Emissions occurring during summerfallow (2.2 Gg N 2 O-N yr -1 ; 6%), in lower portions of the landscape (2.2 Gg N 2 O-N yr -1 ; 6%), and following irrigation (0.7 Gg N 2 O-N yr -1 ; 2%) were partially offset by changes in tillage practices (-1.2 Gg N 2 O-N yr -1 ; -3%) and in coarse-textured soils (-0.2 Gg N 2 O-N yr -1 ; -1%). Differences in N 2 O estimates between Tier I and Tier II approaches mainly arise from the use of lower fertilizer-induced emission factors in the dry Prairie region and the addition of several new N 2 O sources/offsets in the Tier II methodology. Key words: Nitrous oxide, soils, greenhouse gases, inventory
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