Catchment-level evaluation of farmers’ estimates of soil erosion and crop yields in the central highlands of Kenya

Abstract

Soil and water conservation programmes in Kenya were not always successful due to experts’ negligence of the role of farmers in problem identification and conservation planning. Using farmers’ knowledge of soil surface morphology to assess soil productivity may stimulate farmers to participate in solving the prevailing problems. The objective of this study was to compare farmers’ soil erosion and crop yield estimations with a conventional science approach in a small (∼550 ha) catchment in the Central Highlands of Kenya. Farmers’ knowledge and perceptions of the effect of topsoil erosion features was used to assess the soil erosion status across the catchment area. The conventional scientific approach used a survey methodology and GIS-based up-scaling to quantify soil erosion patterns. In addition, the farmers made qualitative estimations of crop yield losses, which were verified through actual crop yield measurements. The soil erosion pattern between the farmers and conventional science approaches showed a strong agreement at the hillslope scale, while at the catchment scale the agreement was slightly weaker. Farmers observed more area under nearly flat and gentle slopes to have high erosion than the area approximated by the conventional science approach. Farmers’ prediction of crop yields loss in each erosion class showed no difference with the actual field measurements. Despite use of farmers’ mapping of erosion pattern being participatory, thereby stimulating awareness creation on land degradation processes, it can be labour intensive and a slower approach than the conventional science approach in evaluating catchment-scale erosion patterns.