Emission factors for N 2 O and NO from agricultural soils in Belgium Pascal Boeckx, Annick Goossens & Oswald Van Cleemput Ghent University Belgium

Lay out Long-term field experiments of N 2 O and NO fluxes from agricultural soils – Field set-up – Results – Emission factors Inventories: IPCC 1996 guidelines – EU-15 – Flanders (Belgium) N 2 O flux modelling Conclusions Future work

Long-term field experiments of N 2 O and NO fluxes from agricultural soils

Field set-up: spatial and temporal distribution Selection of benchmark sites  different of agro-pedological regions different land use intensive agriculture 6 repetitions per field Event-directed monitoring  campaigns per year Monitoring during 2-3 years

Set-up for N 2 O flux measurements: closed chamber and FAID from FAID   to FAID pressure vent 

Results: N 2 O

Emission factor: N 2 O Campaign (> 400 data, 4 soil textures) – N fertilisation: 75 – 506 kg N ha -1 – N 2 O-N emission:0.3 – 31.7 kg N ha -1 – Average EF (95% interval):5.3% ( %) of applied N – Median EF:4.5% of applied N Campaign (> 600 data, 1 soil texture) – N fertilisation: 0 – 414 kg N ha -1 – N 2 O-N emission:2.2 – 10.6 kg N ha -1 – Average EF (95% interval):2.4% ( %) of applied N – Median EF:2.4% of applied N

Set-up for NO flux measurements: open chamber and NOx analyser inlet   outlet

Emission factor: NO WFPS 50% –0.3 – 1.7% of applied N WFPS 90% –1.1 – 7.1% of applied N  Effect on N 2 O-indirect }

Controling factors for N 2 O and NO fluxes Land-use and soil fertility  grassland > arable land N fertilisation  type and application rate Period of the year  soil temperature and moisture Assess the effect size of these factors

Inventories: IPCC 1996 guidelines

N 2 O from agriculture in EU-15

Average N 2 O emission from agriculture 6.3 kton N 2 O-N yr -1 Flanders: IPCC default EF, country specific activity data

Evolution N 2 O from agriculture kton N 2 O-N, EF = 1.25kton N 2 O-N, EF = 3.4 (1.3 – 5.6) Flanders: Uncertainty: 100%

Country specific activity data Belgium: 1991 Uncertainty: 10% ? Country specific animal N excretion factors Country specific dry matter contents of crop residues

Country specific activity data Besides country specific animal numbers, fertilizer application and crop yields use country (region) specific: animal N excretion factors dry matter contents of crop residues NO and NH 3 emission NO 3 - leaching

N 2 O emission modelling

Arable land: empirical model Parton et al. (1996)

Conclusions N 2 O emission factor: 3.4% ( %) / 3.0% – Underestimation of N 2 O from agriculture in Flanders ? NO emission factor:0.3 – 7.1% – Agriculture is a significant NO source (more research !) EF development: – Attention to spatial and temporal resolution, uncertainty National inventories: – Use country specific activity data to reduce inventory uncertainty Modelling: – Underestimation for intensive agriculture

Future work

Future work on N 2 O (and NO) Meta-analysis: statistical tool to compare different independent field experiments to assess the effect size (Hedge ’s index, d) of controlling factors for N 2 O (and NO) emission – Fertiliser N application rate, climate (soil temperature and moisture), soil fertility (C&N-content), texture, drainage and pH Use ‘d’ in empirical modelling Uncertainty assessment via Monte Carlo analysis Link with C sequestration (e.g. effect of no-tillage)