Effect of deforestation on soil fertility on the northwestern slopes of Mt Kenya

Abstract

The area northwest of Mt Kenya is undergoing rapid land use changes caused by a population influx. Rapid population growth and subsequent pressure on land raise the problem of how to increase and sustain agricultural production while at the same time conserving the natural resources (montane forest with Olea africana and Juniperus procera as main species at 2900 m asl.). Deterioration in soil physical and chemical properties following deforestation for agriculture can adversely affect crop production, especially from soils on mountain slopes. Appropriate conservation and management for sustainable use of such soils require monitoring the changes in their fertility. The effects of land clearing for potato cultivation and livestock grazing on the fertility of an Andosol (after 5 to 8 years) were investigated in the 0 to 10, 20 to 30 and 40 to 50 cm soil layers. Topsoil pH decreased significantly in the potato and grass plots, as did organic C, total N and available P. In conclusion, natural vegetation cover maintains and possibly continues to improve sol fertility, whereas agricultural production decreases it through increased erosion and subsequent losses of soil organic carbon and other soil nutrients.