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
was due to the ICC trial with 361 g N2O-N ha -1 y -1 , excluding residues; while more limited discrepancies
resulted from the CIMAS trial (170 g N2O-N ha -1 y -1 as difference of absolute values between model and
IPCC figures). Including residues with both methods, the opposite trend occurred with a greater gap for the
CIMAS trial than the ICC but with lower values for both (67 g N2O-N ha -1 y -1 and 159 g N2O-N ha -1 y -1 for
ICC and CIMAS, respectively).
Table 1: Amounts of N fertiliser applied and estimated N2O-N emissions with the two methods: CERES-
EGC and IPCC (cumulated values over the season were reported over a year period)
Crop Trial
Cropping
system
N applied
with fertiliser
(kg N ha -1 )
CERES-EGC
N2O-N
emissions (g
ha -1 y -1 )
CERES-EGC N2O-
N emissions (g ha -1
y -1 ) including post
harvest period
IPCC N2O-
N emissions
(g ha -1 y -1 )
Winter Wheat ICC PHEP 90a 1791 1976 2380
Barley ICC PHEP 60a 533 723 1542
Barley ICC 50%GHG 80a 312 460 1755
Faba bean ICC PHEP 0 1163 1480 659
Faba bean ICC 50%GHG 0 1246 1871 512
Durum Wheat CIMAS HI 92b +52c 1481 1987 2140
Durum Wheat CIMAS LI 46b +26c 1363 1894 1361
Faba bean CIMAS HI 0 727 876 776
Faba bean CIMAS LI 0 707 836 681
a NH4NO3 N content 33.5%; b Urea N content 46%; c NH4NO3 N content 26%
Cumulated values estimated here showed clearly that the PHEP emissions were on average 1.08-1.32 fold
higher than the 50%-GHG, while HI emissions were 1.06-1.36 fold higher than LI with CERES-EGC, depending
on the estimation method. Higher differences were reported for cereal (on average for all the methods
24%) than for faba bean (mean value among the three methods 11%) (Table 1).
4. Discussion
N2O emission patterns obtained here were in agreement with previous works carried out in Grignon both
with model and continuous chamber measurements (Laville et al., 2011). The pattern obtained for the simulation
underlined the effect of crop residues on the overall N2O emission which is confirmed by other studies
(Barton et al., 2011; Petersen et al., 2011). The effect of residues is also dependent on the farming practice of
the following crop, therefore farm management effects on N2O emissions can be better understood when the
evaluation is carried out at cropping system scale (Mazzoncini et al., 2008; Petersen et al., 2011; Goglio et
al., 2012).
Regarding fertiliser application, it appears from our elaboration that this farming practice had little effect
on N2O emissions, probably in result of a very dry period. Indeed, for the ICC trial, during spring 2011, the
total precipitations during February-May period was 88 mm, when monthly average should be around 50
mm. The same happened for the CIMAS trial, where the total cumulated precipitations in March-May period
were 154 mm concentrated in March; while commonly they are mostly concentrated in April and they are 30
mm greater (Nassi o Di Nasso et al., 2011). Under these conditions, N2O peak emissions would not occur
because of reduced bacterial activity (Bateman and Baggs, 2005; Szukics et al., 2010). Indeed, N2O is emitted
when the soil is wet with WFPS (Water Filled Pore Space) comprised between 55%-70%, depending on
soil type (Bateman and Baggs, 2005; Szukics et al., 2010). Due to limited rainfall, these soil moisture conditions
were partially met (