82 / 104
82
about 9 kg/ha of arable land, compared to a world average of
101 kg/ha (Camara and Heinemaan, 2006; FAOSTAT 2009).
Within Africa, there are strong differences in fertilizer use
between regions, with relatively high use in Northern and
Southern Africa, and very low use (around 1 to 2 kg/ha) in
Western and Central Africa. Taking the increase as proposed
by the Africa Fertilizer Summit as a starting point, this would
mean a growth of the yearly use of fertilizers from 1 to 6 mil-
lion tonnes. Based on the price of fertilizer (DAP) of approxi-
mately US$600/tonne (beginning of 2008), this would mean
US$3 billion/year for the purchase of DAP only. A more mod-
erate price of US$200/tonne would still mean US$1 billion/
year. Added to this are significant costs of and investments in
transport and distribution, developing agricultural research,
extension programs, capacity building, etc. Indeed, there are
many reasons for this low use. One of the reasons is the high
retail prices of fertilizers, especially in areas with poor infra-
structure. A metric tonne of urea costs $90 in Europe, $120
kg in the harbor of Mombassa, $400 in Western Kenya and
$770 in Malawi (Sanchez, 2002).
A major challenge is to find ways of making fertilizer available
to smallholders at affordable prices. There is also a need for
holistic approaches to soil fertility management that embraces
the full range of driving factors and consequences of soil degra-
dation (TSBF-CIAT, 2006). This would include the integration
of mineral and organic sources of nutrients, thereby using lo-
cally available sources of inputs and maximizing their use effi-
ciency, while reducing dependency upon prices of commercial
fertilizers and pesticides. The use of perennials, intercropping
and agroforestry systems, such as the use of nitrogen fixating
leguminous trees, are ways to increase nutrient availability, but
also enhance water availability and pest control, in a more sus-
tainable manner (Sanchez, 2002).
A major challenge is to find ways of making fertilizer available
to smallholders at affordable prices. There is also a need for ho-
listic approaches to soil fertility management that embraces the
full range of driving factors and consequences of soil degrada-
tion (TSBF-CIAT, 2006). This would include the integration of
mineral and organic sources of nutrients, thereby using locally
available sources of inputs and maximizing their use efficiency.
RESOURCES FOR IRRIGATION
Irrigated land area increased rapidly until 1980 with expansion
rates of more than 2% a year. In Asia in particular, it led to a
steady increase of staple food production together with other
elements of the green revolution package (Faures
et al
., 2007).
After 1980, growth in expansion of irrigated area decreased
and it is assumed this trend will continue in the near future.
One of the reasons is that the areas most suitable for irrigation
are already used, leading to higher construction costs in new
areas (Faures
et al
., 2007). Another reason is the strong decline
in relative food prices over the last decades, which makes it less
profitable to invest in irrigation. Current irrigation systems
could be improved by investing in water control and delivery,
automation, monitoring and staff training.
The irrigated area has remained very low in Sub-Saharan Af-
rica and of the land under irrigation, 18% is not used (FAO,
2005b). In most African regions the major challenge is not
the lack of water, but unpredictable and highly variable rainfall
patterns with occurrences of dry spells every two years caus-
ing crop failure. This high uncertainty and variability drive
the risk-averse behaviour of smallholder farmers. Rarely are
investments made in soil management and fertility, crop vari-
eties, tillage practices and even labour in order to avoid losses
in case of total crop failure (Rockstrom
et al
., 2007a,b). Man-
aging the extreme rainfall variability over time and space can
provide supplemental irrigation water to overcome dry periods
and prevent crop failure. In combination with improved soil
management (in regions with severe land degradation, only
5% of the rainwater is used for crops), this should reduce the
risk of total crop failure and enhance the profitability of invest-
ments in crop management, for example, fertilizers, labour
and crop varieties. Increasing crop canopy coverage reduces
evapo-transpiration from the soil, improving soil moisture and
the provision of water for the crop.