Chemistry Reference
In-Depth Information
Table 1
(Continued)
Constraints Occurrence
Characteristics
Use and management
Soil types*
Soils with
drainage
problem
Occur in relatively
flat areas such as
alluvial plains,
depressions, river
valleys and valley
bottomlands that
are subject to
waterlogging
during wet seasons;
they are found in
both semi-arid and
sub-humid regions;
in particular, soils
classified as
Fluvisols and
Gleysols are
developed on a
wide range of
unconsolidated
materials, mainly
sediments.
These are generally poorly
drained soils with very slow
vertical drainage; the
colour ranges from grey to
black; workability is
extremely poor; root
development is hampered
by oxygen deficiency
during the wet periods;
population of soil microbes
is low due to prolonged
waterlogging; other soils in
this category, such as
Vertisols (black cotton
soils), have the capacity to
expand (swell when wet)
and shrink (when dry) thus
affecting crop growth.
Main obstacle to the utilisation of
these soils is the necessity to
install a drainage system. Broad
- bed and furrow systems have
proved successful in the
management of these soils,
especially those classified as
Planosols; furrows should have
very slight slopes to avoid
gullying; large areas under
Vertisols are used for growing
paddy rice, sugar cane, cotton,
teff and subsistence crops while
grazing is common during the
dry seasons; other soils under
this category, such as Gleysols
occurring along the river valleys
are utilised during the dry
seasons for growing vegetables
and horticultural crops which
have a higher market value at
such times. Those classified as
Histosols occur mainly in
wetlands and are therefore best
kept under a permanent grass
cover or under swamps or forest.
Planosols (vlei soils with light
textured topsoil abruptly
over dense subsoil), Vertisols
(black cotton soils), Gleysols
(soils with clear signs of
excess wetness), Fluvisols
(soils developed in alluvial
deposits) and Histosols (peat
and muck soils).
