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Semi-arid agriculture
Land use in Semiarid agriculture is characterized
by subsistence agriculture and nomadic pastoralism, because livestock
is considered an important component in Semiarid communities.
What
is Semi Arid Agriculture?
1.1 Definition
Semiarid agriculture in this context is defined as agricultural
production in semiarid areas constrained by low rainfall,
poor or low nutrient soils, high temperatures, high solar
radiation, and low precipitation.
High transpiration and evaporation rates in vegetated
areas are also dominant hydrological features of Semiarid
agricultural environment. Therefore, natural fragility
of dry land ecosystems renders them extremely vulnerable
to inappropriate land use and exploitation.
Farmers often over-cultivate the few available areas of
fertile land in an attempt to increase production. The
implication of this is that, these dry land communities
are likely to become more vulnerable to climatic variations.
1.2 Characteristics: Land use and Degradation
Land use in Semiarid agriculture is characterized by subsistence
agriculture and nomadic pastoralism. Because livestock
is considered an important component in the livelihoods
of Semiarid communities, degradation has always been attributed
to this sub sector (Sidahmed and Yazman, 1994).
The United Nations Environment Program (UNEP) singled
out human impact and, specifically, livestock grazing
as the cause of the irreversible degradation that has
prevailed during the past two decades (Pearce, 1992).
According to the Word Resources Institute (WRI, 1992),
over grazing is the pervasive cause of soil degradation.
It has been estimated that overgrazing causes land degradation
of 49 and 80% in semiarid regions of Africa and Australia,
respectively.
Rangeland Degradation Since
1945
NOTE:
Percentages indicate the contribution of overgrazing to
total degraded area. Source: WRI (1994)
1.3 Challenges in Semi Arid Agriculture
According to world population statistics, approximately
1bn people live in semiarid regions worldwide and yet
the number of people living and deriving their livelihoods
from the productivity of these marginal lands is growing
by day.
This ever-increasing population is creating a strain on
the existing food sources and thus putting food security
of these areas in jeopardy. Moreover, these less favoured
lands are characterized by erratic weather conditions,
limited rainfall and low soil fertility.
semiarid areas have at least one entirely rainless month/year
and the amount of rainfall ranges from 500mm-1000mm/annum
in most areas. This means that conditions of water deficit,
water stress or drought are common in these areas.
In cases of extreme drought stress, crops yield poorly
or not at all if drought stress during reproductive growth
is severe and persistent.
Changes in severity of drought contribute to dry land
degradation and desertification. This process has been
evident In the Sahel region (West Africa) where rainfall
levels have declined by 20-40% in recent decades accompanied
by severe land degradation.
The amount of rainfall that can be effectively utilized
for crop growth in these lands is also low. This effective
rainfall however, can be increased through water harvesting.
On the other hand, high temperatures also pose serious
limitations in crop productivity especially when water
supply is inadequate. This can be manifested through poor
development of crop yield structures (poor floral initiation)
and ultimately poor yields. Cultivation in semiarid areas
is also associated with long periods of high winds, which
can remove fertile topsoils causing soil erosion.
Challenges related to soils are either due to low nutrients,
presence of alkaline, saline or acidic soils. Majority
of semiarid soils are prone to salinity and this poses
a major constraint to crop production.
In acidic soils, aluminium toxicity has been implicated
in reducing crop growth. All these constraints present
a huge challenge to increasing agricultural productivity
in semiarid areas.
Agricultural researchers, policy makers and other key
stakeholders that are actively involved in promoting or
increasing agricultural productivity in semiarid areas
all seem to agree that the solution to this challenge
lies in sustainable agricultural production.
This concept of sustainable agricultural production entails
improved management of the available and limited resources
and use of improved crop production technologies that
can enhance sustainable production in semiarid areas.
Improved use of the limited resources can be achieved
by managing the natural resources sustainably, for example,
use of soil and water conservation measures to prevent
land degradation (mainly through soil erosion and run
off) and conserve soil fertility and improved use of the
water resources through rainfall harvesting.
Rainfall harvesting defined as capture, diversion, and
storage of rainwater for plant growth (Rosegrant et al,
2002) can increase water availability, soil fertility
and crop production. It can also provide even broader
environmental benefits especially in arid and semiarid
regions.
However, greater involvement of the farmers right from
planning through sensitization/education and implementation
stages is needed to expand the contributions of water
harvesting in sustainable agricultural production and
development in semiarid areas.
Development of appropriate genotypes suitable for the
semiarid environment through appropriate Genetic Enhancement
or Biotechnology Programs will go a long way in increasing
agricultural productivity while ensuring sustainable agricultural
production.
For example use of genetically enhanced early maturing
genotypes or genotypes tolerant to salinity are likely
to be more productive in semiarid areas where water deficits
and salinity respectively, are more severe.
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UNDERSTANDING MILLET
Millets refers to a group of annual grasses
mainly found in the arid and semiarid regions of the
world.
GRANTS
Crop research funded by SFSA aims to
develop new technologies to improve yield and reduce
the risk of crop failure.
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