Documento(s) 9 de 36

Widespread depletion and degradation of soil resources contribute to food insecurity, limit efforts to alleviate poverty, and constrain human development in much of sub-Saharan Africa (SSA). This region supports more than 500 million people, and the population continues to increase by about 3% per year. Yet, in contrast to the situation in most other regions of the world, SSA's per capita agricultural production continues to decline, and soil degradation is a leading cause of this decline. The International Soil Reference and Information Center of the United Nations Environment Programme estimated that by 1991, for Africa as a whole, 5 x 10⁶ ha of productive land had been degraded to the point that rehabilitation was not economically feasible. In addition, some 321 x 10⁶ ha of crop land had been moderately to severely degraded. About 174 x 10⁶ ha currently shows signs of falling production.

In 1997, the United Nations Development Programme reported that in 1993 SSA had the highest incidence of poverty in the world, with 38% of the population, or 220 million people, each living on less than 1 United States dollar per day. Given current demographic and population trends, this level of poverty will affect more than half of the population by 2000. The majority of Africa's poor dwell in rural areas and depend on subsistence agriculture. Women carry out most of the small-scale farming. Collectively, they account for most of the food production. However, they suffer disproportionately from poverty and have inadequate access to the financial resources, technologies, and knowledge that would enable them to restore productivity on their farms. The International Development Research Centre (IDRC), many other international development and research organizations, nongovernmental organizations, and national governments greatly emphasize the need to arrest soil degradation, restore soil productivity, and alleviate poverty in SSA.

IDRC's primary channel for addressing land degradation in Africa and the Middle East is its People, Land and Water (PLAW) program initiative. PLAW's goal is to promote equitable, sustainable, and productive use of land and water resources by rural women and men in stressed ecosystems of Africa and the Middle East to enhance their income, food, and water security. This goal is pursued through research that will lead to better management of the systemic and external factors in both the degradation and the improvement of the productive capacity of land and water resources. PLAW supports the development of local and national policies and institutional arrangements to equitably increase access to and availability and quality of land and water resources. Along with other program initiatives within IDRC, PLAW encourages the exchange of information among stakeholders, with the particular intention of fostering participation of local people in their own development. Through IDRC's research activities, the rural poor become familiar with a range of options for better managing their soils, thereby improving their standard of living.

The many technological approaches to improved soil management include methods for erosion control and the use of intercropping and inorganic fertilizers, including locally available rock phosphates. Nutrient capture and N fixation remain important topics for study. Recently, some investigators shifted their focus from the simplistic provision of soil nutrients for crops uptake to a more holistic understanding of the structure and function of the myriad of physical and biotic components of the soil system. Central to this theme is the management of soil organic matter and associated N fixation through technologies such as using compost, crop residues, animal manure, biomass, ramial chipped wood, improved fallows, hedgerow intercropping (or alley farming), and cover crops.

This publication focuses on the potential of cover crops to maintain and improve soil fertility in SSA. Often in isolation, African researchers have experimented with cover cropping, but the results have not been readily accessible to colleagues and farmers. This book documents past experience with cover crops in Africa, and IDRC hopes it will stimulate future research on socioeconomic and biophysical aspects of this important topic. IDRC anticipates that cover cropping, along with an appropriate mix of other relevant technologies and policies, will eventually lead to improved soil productivity in a number of farming systems.

Don Peden
Senior Program Specialist
People, Land and Water Program Initiative
International Development Research Centre

Documento(s) 9 de 36