GEO Brasil - UNEP

m 3 in agricultural lands and 448 billion
m 3 in pastures, totalling 171 billion m 3
of water This volume does not infiltrate
into the soil or return to lençóis
freáticos Thus, river flood and water
availability declines, which is one of the
hidden reasons behind the energy crisis
recently faced in Brazil
A cross comparison between the map
of use intensity and that of erosion
vulnerability illustrates these
depletions, as presented in Figure 10
Therefore, in the North, where soils have
a high vulnerability to erosion, the
elevated volume of rain makes 98
percent of land less vulnerable to water
erosion, especially because of the little
use of land in agriculture On the other
hand, in the Northeast, climate
limitations make 82 percent of the areas
more vulnerable Although the Central
West is considered less vulnerable in
78 percent of its occupied area, there
are extremely critical zones such as the
surroundings of Pantanal and
important river springs in the formation
of the Amazon River and Paraguay/
Prata river watersheds
Figure 8 - Areas critically subject to erosion due to agricultural practices, as a result of
combining land use and the soil’s vulnerability to erosion.
5
0
-5
-10
-15
-20
-25
-30
-70
-65
-60
-55
-50
-45
-40
-35
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–
+
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500km
Geographic Proj.
Datum: SAD69
the state of the environment in Brazil
In the South, 40 percent of the land is
highly vulnerable, which indicates that
soils with a higher vulnerability to
erosion are being overexploited
However, since the 1980s, there has
been an increasing adoption of soil
handling systems aiming at
preservation based on Direct Planting
in 85 percent of area cultivated yearly
and integrated handling programmes
in watersheds This measure has been
changing the critical situation
previously described towards a path of
sustainable agriculture
Erosion generates a total annual
depletion of 15,2 million tonnes of
Dolomitic Rock Lime (23 percent of
CaO), which has an estimated cost of
R$563 million; 879,000 tonnes of Triple
In addition, it is essential to highlight
the inadequacy of dirt roads in rural
and periurban areas– especially related
to land distribution schemes and land
occupation by low-income population
The impact caused by erosion is due
to inadequate execution or
preservation (Bertolini & Lombardi
Neto, 1993) Several forecasts point to
the aggravation of erosion as a
consequence of climate changes likely
to occur in the next century (Williams
et al, 1996 e Williams, 2000)
32 Soil fertility depletion
Modern fertilisation practices were
implemented more than one century
ago They are based on the concept of
plant nutrition and have contributed a
great deal to increase agricultural
production and improve the quality of
food, forests, forage and agricultural
production Improvement of soil
fertility through the use of fertilisers,
as well as plant improvement,
increased crop productivity between
1970 and 1998, resulting in an economy
of land use in Brazil - 60 million
hectares This area could have been
even larger if fertilisation were a more
widespread practice in the country
Brazilian soils are generally acid, poor
in phosphorus, calcium, and
magnesium and rich in toxic elements
(aluminium, manganese and iron);
however, the quantity of fertiliser and
corrective applied is much below the
recommended level Because of
excessive acidity, about 75 million
tonnes of lime should be used
Although the installed capacity for
mining and processing is currently 50
million tonnes per year, only 15 million
63