World Agroforestry Centre - Transforming Lives and Landscapes

Solving Africa's Soil Crisis

Over 230 million people in sub-Saharan Africa are chronically hungry. Soil degradation and meagre crop yields are partly to blame. Unfortunately, efforts to improve soils have been hampered by a serious lack of knowledge about soil conditions. A new project, launched in 2008, is tackling the problem.

The population of sub-Saharan Africa has more than doubled since 1970, and it may double again in the next 30 years. Land holdings have steadily shrunk in size and many farmers, unable to leave their land fallow, grow the same food crops, year after year, on the same plot of land. The vast majority cannot afford mineral fertilizers to replenish their soils and the result has been severe land degradation, declining yields and malnutrition.

The African Soil Information Service (AfSIS), funded by the Gates Foundation and the Alliance for a Green Revolution in Africa (AGRA), will revolutionize our understanding of Africa’s soils. The World Agroforestry Centre, one of four international research organizations involved in the project, is responsible for analysing and evaluating soil properties.

“For us, this is very exciting,” explains the lead soil scientist, Keith Shepherd. “We are using soil surveillance principles which we helped to develop in West Africa and elsewhere, and infrared spectroscopy techniques which we’ve refined over the years in our laboratories in Nairobi.” The Centre recently extended these techniques to include new x-ray and laser technology, maintaining the theme of only using light to rapidly analyse soils.

During the four-year project, tens of thousands of soil samples will be taken from at least 60 randomly selected sites, each measuring 100 square kilometres. The data will then be statistically modelled and combined with data from satellite images and other geographic databases, and a process of extrapolation will enable the scientists to create high-resolution maps that provide a picture of soil health across the whole of sub-Saharan Africa.

The maps will provide detailed information about the main constraints to crop productivity, such as a lack of phosphorus or a susceptibility to erosion. “We will also be able to make comparisons between undisturbed land and cultivated land, and come up with various indices of soil health,” explains Shepherd. The project will provide information about the impact of cultivation on soil carbon stocks, and the carbon storage potential of different soil types. This could be particularly useful for countries negotiating deals which will reward them for sequestering or storing carbon as a measure to reduce the level of greenhouse gases in the atmosphere (see also pages 8 to 10).

During recent years, scientists working in Africa have developed a new approach to improving soil health, known as integrated soil fertility management, which combines the use of organic and inorganic fertilizers. However, a lack of information about soil health has proved a barrier to its adoption on a large scale. The information gathered by AfSIS will not only hasten its spread, but provide farmers, extension workers, agricultural ministers and others with information which will enable them to improve soil management, and in doing so tackle one of Africa’s most pressing problems: hunger.

“Soil management must be dramatically improved if we are to reduce poverty, feed growing populations and cope with the impact of climate change on agriculture.”
Nteranya Sanginga

About 500 million hectares of sub-Saharan Africa’s agricultural land is moderately or severely degraded.

“Helping smallholder farmers increase their yields and incomes is one of the most important things the world can do to alleviate hunger and poverty.”
Rajiv Shah

Cheap, quick, accurate

Scientists at the World Agroforestry Centre are using infrared, x-ray and laser spectroscopic techniques to analyse soils. These are cheap, accurate and easy to use. The new instruments provide accurate information that greatly increases the likelihood of agricultural and development projects achieving their goals.

When used by research and development programmes, the surveillance approach eliminates the guesswork involved in matching improved agricultural technologies to specific soil types. Although the World Agroforestry Centre adapted the new analytical techniques to increase agricultural productivity, they can also be used to plan and monitor environmental programmes. For example, in East Africa infrared spectroscopy has been used to identify the source of pollution that threatens Lake Victoria.

"We are confident that within 10 years, soil laboratories in developing countries will be using the new spectroscopic techniques, and traditional methods using chemical extractions will become obsolete," says Keith Shepherd.