Agriculture Reference
In-Depth Information
Therefore, the agro-ecosystem plays a key role in the sustainability of world life, since
the exponential growth of global population will lead to an increased food demand. A recent
approach to mitigate the dependence of fossil fuel has been the prospect of producing
alternative energy from plant biomass. Table 1 shows the global extent of agricultural lands,
referred to year 2009, providing the potential role of the agriculture on the environmental
damage. At present, more than 1.5 billion ha, about 12% of the world land area, is used for
crop production (FAO, 2013). World agricultural production grew on average between 2 and
4% per year over the last 50 years, while the cultivated area (permanent cropland and arable
land) grew by only 1% annually. More than 40% of the increase in food production came
from irrigated areas, which have doubled in size (FAO, 2013).
Nitrogen removed by the harvesting consequently reduces in the nitrogen available in the
soil for the next crop cycle. Loss of nitrogen soil fertility is recovered by means of mineral
fertilizers, whose production requires a large amount of fossil fuel (Haber-Bosch process). In
addition, human activities increase the input of reactive nitrogen (Nr; defined as all nitrogen
compounds other than N
2
) into the biosphere that currently exceed the rate of biological N
2
fixation in native terrestrial ecosystems (Galloway et al., 2004). The increase of reactive
nitrogen is due not only by fertilizer production, but also by the fossil fuel combustion used to
support food and energy demands. High mineral nitrogen fertilization represents one of the
main human agricultural practices with high environmental emission of pollutants into the
atmosphere, soil and water.
Table 1. Global extent of the agricultural lands referred to the year 2009 (FAO, 2013)
Agricultural
surface
(%)
Agricultural
surface
(thousand ha)
Permanent
crops
(%)
Permanent
meadows and
pastures (%)
Arable
(%)
Mainland
World
37.6
4,889,048
28.3
3.1
68.8
Africa
39.2
1,161,062
19.3
2.5
78.4
Latin America and
Caribbean
35.7
722,358
20.7
2.8
76.5
Northern America
25.3
471,290
44.1
2.1
53.8
Asia
53.0
1,638,836
28.9
4.7
66.7
Europe
21.4
472,631
58.8
3.3
37.9
Oceania
49.8
422,870
11.4
0.4
88.2
Melanesia
3.9
2,090
22.2
46.6
31.3
Micronesia
30.4
96
9.4
73.0
27.4
Polynesia
20.3
164
30.7
52.7
19.0
Table 2 reports the global nitrogen fertilizer consumption referred per ha of arable land
and permanent crops for 2009. Nitrogen fertilizer consumption is measured by the quantity of
nitrogen nutrients used for plant nutrition per unit of arable land. Today, Asian farmers are
the major users of fertilizers (Table 2). One -third of the increase in cereal production
worldwide and half of the increase in India's grain production during the 1970s and 1980s
have been attributed to increased fertilizer consumption (FAO, 2013). It has been estimated
that, on average, only about 50% of the N applied as fertilizer is actually available for near-
term crop production. Global per capita rates of nitrogen fertilizer consumption per year have
risen from 0.2 kg in 1900 to 2 kg in 1950, to nearly 14 kg in 2000 (Smil, 2001).
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