Soil fertility management in sub-Saharan Africa

Abstract

This report is a critical review of the technical, economic, and institutional constraints to improving soil fertility in Sub-Saharan Africa (SSE), and actions recommended to address them. The report is a review of selected literature, illustrated by a synthesis of the most important lessons from four country action plans prepared for Ghana, Kenya, Malawi, and Mali. The action plans were formulated by country researchers to identify ways to improve soil fertility in their respective countries. The work was financed by the UK Department for International Development, Natural Resources and Rural Livelihoods (DFID, formerly ODA), the managed by the World Bank. Each of the country reports examined: a) the demand and supply (procurement, distribution, and marketing) of mineral fertilizers; b) the exploitation of local mineral resources; c) preventing oil erosion and increasing soil-water treatment, from the point of view of both their value to soils and their value as investments; d) soil fertility management using organic technologies and management practices. The report is addressed to planners, agricultural researchers, and practitioners in SSA, and aims to provide a framework for actions to improve soil fertility management. Recommended interventions for planners include policies affecting farm-gate prices for purchased inputs and agricultural products, ways to achieve more efficient fertilizer supply and distribution, for researchers and practitioners targeting additions of plant nutrients from mineral and organic sources, improved on-farm crop and soil organic matter management, and research and technology dissemination. There are strong linkages between policy interventions and technical approaches. The report makes an effort to identify constraints and recommend actions and enabling principles that are common to Africa as a whole, while acknowledging that the unique physical, economic, and institutional environments in each country will determine the relative importance of the actions and principles presented. Following defintions of soil fertility, and discussion of its importance, the report reviews promising technical solutions to the problems described in the introductory section. These solutions include proposals for improving soil organic matter through the use of organic inputs, crop response rates to mineral fertilizers and recommended mineral fertilizer application rates, the exploitation of local mineral resources, and soil and water conservation practices. The report analyzes reasons why solutions that look promising on research stations may not be taken up by farmers. It focuses on such farmer characteristics as lack of knowledge, limited resources, and inability to bear risk. The failure of agricultural researchers to understand fully these characteristics, and take them into account, leads to solutions whose technical and economic elements do not respond to farm situations, and therefore offer limited profitability to farmers. The report also evaluates the impact of economic policies, and the unavailability of critical inputs. The report describes how agricultural research and extension can do better in adapting promising solutions to actual conditions facing smallholder farmers. It includes examples of such better adaptation from Kenya, Malawi, Mali, and Ethiopia. Finally, the report presents a summary action plan and recommended actions for agricultural researchers, government policy makers, the private sector, and aid donors.