Agriculture Reference
In-Depth Information
Figure 11.7
A map of Brazil showing the main distribution of Nitossolos.
Grouping of soils showing strongly weathered pedological development along
with kaolinitic-oxidic soil genesis, resulting in intensive weathering of both less resistant primary
and secondary minerals, except for hydroxy interlayer vermiculites. They have a latosolic B horizon,
which is at least 50 cm thick immediately below any surface diagnostic horizon except histic H
horizon. The CEC is less than 17 cmol
LatossolosÐ
/kg of clay; texture sandy loam or Ýner; has less than 4%
of weatherable minerals and less than 6% of muscovite in the sand fraction. They do not have more
than trace of smectite and have less than 5% by volume showing rock structure. The silt-clay ratio
is less than 0.6 for soils having more than 35% clay, and 0.7 for soils with less than 35% clay.
They also have gradual to diffuse boundaries between the subhorizons.
This class includes mainly those soils that have been previously identiÝed as Latossolos, except
a few varieties identiÝed as Latossolos Plinticos.
The geographical distribution of this soil class secluded from the 1:5,000,000 scale of the
Brazilian soil map is shown in Figure 11.8. It comprises 3,277,096 km
c
corresponding to 38.5%
2
of the country.
Grouping of soils showing rather moderate weathering resulting from bisiali-
tization process, resulting in a highly saturated exchange complex with mainly calcium as basic
exchangeable cation. They have a chernozemic A horizon overlying a cambic B, textural B, or a
nitic B horizon. All B horizons have both CEC of the clay fraction equal to or higher than 27cmol
ChernossolosÐ
/kg
of clay, and base saturation of 50% or more, with or without either a calcic horizon or carbonatic
properties. They lack diagnostic characteristics of Vertissolos, Planossolos, and Gleissolos.
This class includes mainly those soils that have been previously identiÝed as Brunizem, Rend-
zina, Brunizem Avermelhado, Brunizem HidromrÝco.
The geographical distribution of this soil class secluded from the 1:5,000,000 scale of the
Brazilian soil map is shown in Figure 11.9. It comprises 42,559 km
c
corresponding to 0.5% of the
2
country.
Grouping of weakly developed soils having a cambic B horizon. Little devel-
opment with features representing genetic soil development without extreme weathering; showing
stronger chroma and redder hue than the underlying horizon. If the cambic B horizon occurs under
a chernozemic A horizon, it must have either a low-activity clay (CEC less than 27 cmol
CambissolosÐ
/kg of
clay) or base saturation less than 50%. The cambic horizon may occur immediately below any kind
c
