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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.