Rationality of farmer perception of soil erosion : The effectiveness of soil conservation in semi-arid Kenya

Farmer perception of the dangers of soil erosion is increasingly recognized as having a rational basis. Little independent corroboration exists, however, that farmer behaviour accords with the technical efficiency and cost effectiveness of soil and water conservation measures. Accordingly, at three field sites in semiarid Kenya, five conservation treatments — bench terraces (fanya juu), tied ridging, contour tillage, trashlines and a control treatment (hand tillage) — were assessed for their performance and compared with farmersʹ views of the need for conservation and their actual adoption of soil and water conservation measures. Experimentally in terms of differential maize yields, trashlines were found to be the single most effective measure for most (but not all) circumstances. Analyses of marginal rates of return and net present values over ten years indicated tied ridging and terracing also to be worthwhile but only under specific circumstances of soil quality and labour availability. A questionnaire survey in the three trial areas revealed that farmersʹ opinions and rate of adoption of techniques closely match the conclusions from the experimental plots. Small farmer behaviour is rational in this marginal and difficult environment.