Agriculture Reference
In-Depth Information
Table 11.3
Frequency of Occurrence of Soil Order Classes in Brazil
Soil Order
Area (km
2
)
ercent
Soil Order
Area (km
2
)
Percent
Alissolos
374,525
4.4
Luvissolos
178,610
2.7
Argissolos
1,711,040
19.8
Neossolos
1,251,255
14.7
Cambissolos
229,822
2.7
Nitossolos
110,655
1.3
Chernossolos
42,559
0.5
Organossolos
1
Not Significant
Espodossolos
136,191
1.6
Planossolos
153,214
1.8
Gleissolos
323,453
3.8
Plintossolos
510,716
6.0
Latossolos
3,277,096
38.5
Vertissolos
8512
0.1
1
Usually associated with Gleissolos.
horizon and having a textural B horizon with high-activity clay. Finally we have a group of soils
with both a textural B horizon and low-activity clay.
This is a conventional approach and we believe that, with a small amount of training, most soil
scientists and other users of the soil information can identify the soil order without too much
difÝculty. This is important for agronomists, soil fertility specialists, and land evaluation specialists,
as much of the land use recommendations are still based on the highest level of the classiÝcation.
At this moment, environmental applications of soil information is still limited. But as our knowledge
base on environmental and other applications of soils grows, we will modify the system accordingly.
DISTRIBUTION OF SOILS IN BRAZIL
The Latossolos order is the most extensive soil class comprising about 38.5% of the Brazilian
Territory. Considerable areas are on the central plateaus, on the lower portion of the Amazon River
Basin, and signiÝcant areas on the upper part of the Paran River Basin in the South region. This
class is followed by the Argissolos, with about 19.8%, and they occur mainly among the latosolic
plateaus on the Brazilian rock shield. Together they represent about 58% of Brazilian soil classes.
The Neossolos Class is the third in area, representing 14.7% of the total area. The Plintossolos
class is the fourth most extensive, performing 6% of Brazilian soils. This class commonly occurs
on pediments and/or on the footslopes of plateaus. The other classes occur at lower percentages,
as shown in Table 11.3. The Organossolos, in terms of Brazilian soils, occupy very small areas,
and they always occur in association with the Gleissolos. The distribution of the soil classes at
Order category is shown in Figure 11.14.
CONCLUSION
The elaboration of any soil classiÝcation is inÞuenced by the knowledge of soil formation and
genesis. The selection of differentiating criteria and attributes for setting apart soil classes in the
higher categories was guided by grouping similar soils based upon ease of identiÝcation of mor-
phogenetic features in the soil environment. These are believed to carry out expressive amounts of
accessory characteristics that commonly have great importance for agricultural use and management
requirements of each class. The current Brazilian system represents a major reorganization of the
outline of the restricted distribution of the fourth approximation, which circulated in 1997 among
the partners. The system comprises 14 orders, frameworked in six categorical levels in a hierarchy
of increasing information content for the known Brazilian soils. It is an open system that allows
inclusion of classes if it becomes necessary to introduce new one. The Brazilian system was
published in 2000, and presents adaptations of criteria and concepts established in Soil Taxonomy
and in the World Reference Base for Soil ClassiÝcation. However, the structure of the system and
emphasis given to criteria differ from these international systems. The system is not considered a
 
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