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

PARALLEL SESSION 4C: CROP PRODUCTION SYSTEMS 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
of phosphorus emission and the use of mineral fertiliser (the main source of phosphorus being poultry manure).
3.3. Variability of impacts and cropping system characteristics as explained by the clustering
The optimal number of clusters minimizing the distance between fields in a group and maximizing the
distance between groups was 4. The cluster tree and characteristics of each nod are showed in Figure 1.
Figure 1. Hierarchical tree presenting the 4 clusters with positive (+) or negative (-) variations for the dimensions
of PCA and correlated cropping system characteristics. For each cluster paragons are identified by ‘p’
Cluster one (C1) was negatively correlated to dimension 1. Accordingly, C1 showed significantly less impact
for OD, MET, FD, POF and GWP (v-test>2), which were the impact categories correlated to dimension 1. In
addition, cluster 1 showed significantly lower values for three additional variables: crop duration, number of
irrigation and water supply (v-test>|2|). The LCIA results of the paragon P7 for cluster 1 were less than that
of P38 (representative for the whole population) for almost all impact categories except for FE and MD.
N,P,K-fertiliser manufacturing was pinpointed as the main contributor for impact categories correlated to
dimension 1. Conversely, Cluster 4 (C4) was positively correlated to dimension 1 and showed significantly
greater impacts for HT, MET, OD, FD, GWP and POF (v-test>2) than the overall population. In addition, C4
was positively correlated to the number of water pumping hours during both the nursery and the field stages.
For categories correlated to dimension 1, the LCIA results for the paragon P40 were two fold greater than
that of the reference P38 and the main contributor was clearly energy use for irrigation.
Cluster 2 (C2) was positively correlated with dimension 2 and had significantly greater TET and FET impacts
than the overall population. C2 showed significantly greater values for the number of pesticide applications,
as a result of a larger number of insecticide applications. The application rates of insecticides were also
greater for cluster 2. Similarly, cluster 2 showed significantly greater values for the number of fertiliser applications,
correlated to the number of mineral fertiliser applications. Moreover, C2 was negatively correlated
to sowing date and planting date, suggesting that, the earlier was the crop cycle, the higher were input
levels for those fields. LCIA results of the paragon P6 for cluster 2 further supported these results, highlighting
insecticides application as main contributor for both TET and FET. Finally, cluster 3 (C3) was negatively
correlated to dimension 3 and showed significantly greater impacts for FE and MD. C3 showed significantly
higher values for mineral nitrogen application rates. The LCIA results of P17 showed high contribution of
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