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Developing stratified N2O emission factors for Europe
Adrian Leip1, Wilfried Winiwarter2
AbstractN2O fluxes from agricultural soils have only limited dependence on the amount of nitrogen added to the soil in the year of crop growth. Amongst the many factors that influence the magnitude of N2O fluxes are soil parameters (organic carbon content, soil texture and pH), ways of fertilizer application (types of fertilizer applied, timing) and meteorological conditions. Yet, in most assessments of anthropogenic GHG fluxes from agriculture, constant emission factors are used, in many cases the default IPCC factors of 1.25% or 1.0% of total anthropogenic N-input.
We investigate the possibility to replace this – so-called Tier 1 – approach with stratified emissions functions that take into account both N-input and the spatial variability of the environmental conditions.
There is a annual large variability in the data with simulated median N2O fluxes for EU27 ranging from 1.5 to 2.4 kg N2O-N ha-1 y-1. A second-order polynomial fit gives high coef-ficients of determination (>0.999); a linear regression of N2O fluxes against mineral (manure) N-input gives fertilizer induced emissions (FIE) between 0.9%-1.2% (1.1%-1.5%) (arithmetic mean). However, results at national level are very heterogeneous as shown in the examples of the frequency distribution plots for a few countries.
ResultsAverage simulated N2O fluxes for EU27 are log-normally distributed. There is a clear difference of simulated N2O fluxes in the organic and extensification scenarios. Median simulated N2O fluxes for the default scenario is 1.9 kg N2O-N ha-1 y-1. Arithmetic mean is 4.3 kg N2O-N ha-1 y-1.
FIE mineral fertilizer nitrogen
FIE manure nitrogen
1990 0.9% 1.3%
1991 0.9% 1.2%
1992 1.1% 1.6%1993 1.2% 1.2%
1994 1.1% 1.6%
1995 1.1%` 1.4%1996 1.2% 1.1%
1997 1.2% 1.5%
1998 1.13% 1.2%
1999 1.2% 1.6%
2000 1.2% 1.2%
All years 1.1% 1.4%
Adrian LeipEuroean Commissions – Joint Research CentreInstitute for Environment and SustainabilityTel.: +39 0332 786327e-mail: [email protected]
Wilfried WiniwarterInternational Institute for Applied System Analysise-mail: [email protected]
ScenariosS00 Default: downscaled from CAPRI databaseS01-S05 Response to mineral fertilizer application of Nmin set to 1.25, 1.1, 0.9, 0.75, 0.5 of defaultS07-S12 Response to manure nitrogen application of Nman set to 1.25, 1.1, 0.9, 0.75, 0.5 of defaultS06,S13 Organic farming manure nitrogen only with available manure (S06) or same total N-input (S13)S14 Extensification manure nitrogen only, reduced yieldS15 Precision farming mineral fertilizer according to crop's needs (not yet simulated)S16 Nitrate Directive maximum of 170 kg N/haS17 Renewable Energy Directive assessment of CAPRI scenarios
MethodologyWe use the process-based model DNDC-EUROPE (Li et al., 2000, Leip et al., 2008) to simulate N2O fluxes at a large number of spatial calculation units (about 200,000 for EU27) for different scenarios. Each unit is simulated for up to three crops and for ten different meteorological years. The results presented are based on a total of about 10,000,000 individual simulations.
Conclusions According to the DNDC model, there is a clear relationship between N-input and N2O fluxes Average fertilizer-induced emissions (FIEs) are 1.1% of mineral fertilizer and 1.35% of manure-nitrogen. National FIEs are ranging
from 0.5% to 2% of mineral fertilizer-N and 0.2% to 5.6% for manure-N. However, not for all countries a clear relationship between N-input and N2O emissions was found.
N2O flux [kg N2O-N ha-1 y-1]
Fre
quen
cy
Mean application rate of manure: 50 kg N ha-1 y-1 Mean application rate of mineral fertilizer: 130 kg N ha-1 y-1
