EROSION-CROP PRODUCTIVITY RELATIONSHIPS FOR SOILS OF AFRICA

Soil erosion and land degradation are severe problems in Africa. Some quantitative information on the magnitude of soil erosion for different soils and ecoregions is available. However, quantitative data on effects of erosion on crop yields under different systems of management are available only for a few sites. The objective of this review is to use existing data on erosion rates and productivity relationships to estimate losses in crop yield due to past erosion at the continental level. The available information is also used to predict losses during the next 30 yr. Analyses of the available data indicate that yield reductions due to past erosion may range from 2 to 40%, with a mean of 8.2% for the continent and 6.2% for sub-Saharan Africa (SSA). If accelerated erosion continues unabated, yield reductions by the year 2020 may be 16.5% for the continent and 14.5% for SSA. Annual reduction in total production for 1989 due to accelerated erosion in the continent was estimated at 8.2 million Mg for cereals, 9.2 million Mg for roots and tubers, and 0.6 million Mg for pulses. The reduction in total production in 1989 for SSA was estimated at 3.6 million Mg for cereals, 6.5 million Mg for roots and tubers, and 0.36 million Mg for pulses.