LCA Food 2012 in Saint Malo, France! - Manifestations et colloques ...

PARALLEL SESSION 2B: EMISSIONS MODELLING 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
two crop rotations 4 different fertiliser treatments were applied: zero fertiliser, solid beef cattle manure from
feedlots, ammonium nitrate, and ammonium nitrate combined with solid manure. Since the publication by
Ellert and Janzen (2008) provides no data on the achieved crop yields during the years under study and these
are needed in the model to calculate the C input flux and the amounts of crop residues, average yield data for
Alberta, Canada was taken from official statistics of the respective years (Alberta Agriculture and Food,
2007). Data on N content, yields and amount of residues from alfalfa after consecutive years of cultivation
were taken from Jung (2003). All other crop residues were determined using the default factors for estimation
of N added to soils from crop residues within the IPCC guidelines (IPCC, 2006). The C:N ratio of the
Chernozem soil on which the study was carried out was taken from FAO (2001). Additional information on
nutrient composition of solid beef cattle manure from feedlots not provided in Ellert and Janzen (2008) were
taken from Kissinger et al., (2007).
2.3. Model comparison
We further calculated N2O emissions with our model using data from an organic long-term field trial at the
Research Institute of Organic Agriculture (FiBL), Switzerland, which compares effects of reduced versus
conventional tillage on soil quality (Berner et al., 2008). From this field trial measured data on soil carbon
stocks, amounts and composition of fertilisers used and crop yields are available. Beef cattle slurry was used
as organic fertiliser. The N2O emissions determined by our model were compared with the emissions’ calculations
from the IPCC model. Regarding indirect N2O emissions only emissions through volatilisation of N
as NH3 were considered in the comparative calculations using an emission factor specific to Switzerland.
3. Results
The correlation of simulated direct N2O emissions with the measured values from the study of Ellert and
Janzen (2008) is strong with a correlation coefficient of around 0.84 (Fig. 2). The 4 different fertiliser treatments
were modelled with high reliability.
Figure 2: Simulated versus measured N2O emissions (Ellert and Janzen, 2008) from two different crop rotations
and 4 different fertiliser treatments each used to test the model.
The comparison of calculations from our model with calculations from the IPCC model (IPCC, 2006) using
data from an organic field trial yielded 9% lower emissions on average over the entire crop rotation for
the conventional tilled plots (Table 1). For the reduced tilled plots our model calculations resulted in 23%
lower emissions on average over the entire crop rotation than the emissions calculated with the IPCC model.
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