Agriculture Reference
In-Depth Information
Table 2. Mainland data of nitrogen fertilizer consumption referred per hectare of arable
land and permanent crops for 2009 (FAO, 2013)
Mainland
N (kg ha
-1
)
World
69.3
Africa
11.0
Latin America and Caribbean
49.2
Northern America
58.9
Asia
128.1
Europe
44.1
Oceania
22.6
Melanesia
18.2
Micronesia
0.0
Polynesia
39.4
The environmental loading of the nitrogen fertilizers is due first to the various activities
of the technological subsystem (production, transport, application), second to the alteration of
some soil microbial processes and third to the excess supply not absorbed by the cultivated
crop (Figure 1).
Holistic and systemic approaches are useful in studying complex systems, such as the
agro-ecosystem. The present chapter will review the state of art of the environmental impact
of nitrogen fertilization by analyzing the effect caused by the interactions of the technological
and environmental subsystems. The environmental loads connected to the technological
subsystem will be described by means of Life Cycle Assessment (LCA) approach. The Life
Cycle Assessment is a method able to quantify the environmental aspects and the potential
impacts associated with a product, process, or activity throughout its entire cycle of life. The
analysis is done at all stages, from extraction of raw materials, through production, use and
maintenance, to decommissioning at the end of life. The procedure is in accordance with the
ISO 14040 and ILCD Handbook. LCA has been used to evaluate the cradle-to-grave
environmental impacts of agriculture-based products since the late 1990s. As shown in
several LCA studies, the agricultural system can be a main contributor to environmental
burdens. Among the main concerns are trace gas emissions and leaching losses associated
with nitrogen fertilizers usage on agricultural lands. These are due to pedo-climatic conditions
and site specific agricultural management (Figure 1). In particular, the agricultural activities
linked to mineral nitrogen fertilization contribute considerably to the emissions of greenhouse
gases (GHGs) such as CO
2
, CH
4
, N
2
O along with trace gases (NH
3
and NO
x
) and NO
3
-
leaching. For this reason in an LCA study, direct field emission (DFE) of these compounds
has to be as much as it is possible representative of local pedo-climatic conditions and
cultivation.
In addition, the purpose of this chapter is to describe in detail the effect of nitrogen
application on soil microbial activities responsible for the production of atmospheric
pollutants (carbon dioxide, methane, nitrogen compounds) and nitrogen dispersion in bodies
of water.
Moreover, mitigation strategies for both sub-systems suitable for reduction of the
environmental impact in the use of nitrogen fertilizers will also be reported.
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