Soil erosion in Swaziland: A synthesis

The main conclusions of the research project on soil erosion and sedimentation in Swaziland are as follows. (1) Soil erosion has worsened over the last 20 years. The proportion of an 1800 km² study area in the Middleveld classified as ‘high erosion class’ has increased from 6.7 to 13.6% between 1972 and 1990. (2) Gully erosion is the main process and is concentrated within the Manzini, Jabuleni, Lobamba and Chibidze land systems, all characterised by soil-saprolite complexes. (3) Overgrazing and compaction along paths and tracks lower the infiltration rate of the clay-rich ferralitic soils, promoting surface runoff and the formation of rills. (4) Once the rill deepens and cuts through the soil on to the underlying saprolite, gullies develop rapidly because of the low shear strength of the material. (5) Soil erosion problems are compounded by the existing system of land tenure and increasing pressure of livestock and population on the land. (6) In some instances, population pressure can lead to improvements in land management and better soil protection. Recommendations for controlling soil erosion and for further research are presented.