Environmental Engineering Reference
In-Depth Information
high fertilization rates, with N
2
O flush which concentrates on few days of very
high emissions (<20). At intermediate values of fertilization the average emitting
period lasts slightly more than 30 days arriving at a maximum of 56 days.
9.5 Conclusions
The difference in EFs found between data obtained in Italian experimental sites of
maize and the data calculated using IPCC' and Bouwman et al. (
2002b
) empirical
equation, suggests that climate might have a stronger influence on N
2
O emissions
rates than soil characteristics, for a given input of Nr. This poses a clear problem
in terms of availability of representative data for specific climatic areas.
The few available data from Bouwman dataset, which are derived from
Mediterranean climate sites, report an EF of 0.28 % for Spain (Andalusia 3 sites,
Catalonia 3 sites) and 0.5 % for 3 sites in Modena. Both values are closer to the
presented estimates on maize (0.3-0.7 %) rather than to the 1 % by IPCC average
estimates. Averaging the above reported estimates for Mediterranean climate sites,
we might indicate an average EF of 0.45 % 0.2 as a more realistic estimate than
1 % for most of the crops of the Italian peninsula excluding areas which might
already belong to climatic areas not specifically classified as Mediterranean.
However, the present study has also further evidenced that the relationship
between Nr addition and FIE is not linear, so that the EF will change for increas-
ing Nr addition rates. The empirical equation calculated in this study (Fig.
9.1
)
could then be applied to calculate the FIE rather than a simple EF when climatic
conditions resemble those encountered in this study. This would take into account
both the climatic impact and the fertilizer addition rate.
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