Chemistry Reference
In-Depth Information
Table 1
(Continued)
Constraints Occurrence
Characteristics
Use and management
Soil types*
Soils with soil
fertility
problem.
Variable - virtually
all soils in sub-
Saharan Africa
have fertility
problem.
Low fertility and insufficient
organic matter are the main
soil characteristics that
adversely affect crop
production in the region;
most of the soils are highly
weathered, having
undergone both
ferrugination and
ferralitisation processes,
have low pH and high levels
of aluminium toxicity which
interfere with nutrient
uptake; nitrogen (N) and
phosphorus (P) are the
most limiting nutrients and
so are the low levels of
organic matter; low soil
fertility results from
nutrient depletion - erosion,
crop harvest leading to
negative nutrient balance,
leaching and inadequate
crop fertilisation.
Used for extensive grazing and for
growing a wide range of
subsistence and cash crops, both
annual and perennial. Requires
heavy application of both
organic and inorganic fertilisers
including liming, depending on
levels of soil pH. Appropriate
agronomic practices, soil and
water conservation measures are
required for soil moisture
conservation as well as for
minimising water erosion (see
Figure 1).
A wide range of soils in the
region fall under this
category. However, those
classified as Ferralsols are
naturally chemically poor as
most of the primary minerals
have weathered, resulting in
soils having low cation
exchange capacity (CEC) of
,16 meq. Thus maintaining
the SOM content by
manuring, mulching or
adequate fallow period and
prevention of erosion are
important management
requirements.
