The roots of the matter Soil quality and tree roots in the Sahel

摘要

In the semi-arid Sahel region of West Africa, population pressure has increased to such an extent that there is little possibility of increasing agricultural production by expanding the amount of land under cultivation; most of the suitable land has already been put into production. The best option in the Sahel is to increase yields on existing fields. Although rainfall is limited, the biggest obstacle farmers face is the low-and often decreasing-soil fertility (Van der Pol 1992, Van Keulen and Breman 1990). This means that lasting and improved agricultural productivity hinges largely on improving the efficiency of nutrient use. And efficient use of nutrients may, in turn, be improved by trees, although this depends on the structure and function ofthe tree roots.