Soil Use and Management (2004) 20, 23±31 DOI: 10.1079/SUM2004217 Increasing the relevance of scienti®c information in hillside environments through understanding of local soil management in a small watershed of the Colombian Andes T. Oberthu Èr 1, *, E. Barrios 2 , S. Cook 1 , H. Usma 1 & G. Escobar 1 Abstract. This article explores the question of how scienti®c information can improve local agronomic management using concepts of uncertainty classi®cation and uncertainty management. Information and data on local management of soil fertility based on a local classi®cation system of soil quality were collected from a small watershed in Cauca (Colombia). The analyses suggest that farmers hold local knowledge about soils at two levels. The ®rst is based on empirical observations and refers to local knowledge about soils and landscape, which shows that the classes identi®ed in the local soil quality classi®cation are consistent with results obtained using measured soil parameters. At the second level, farmers have some awareness of ecolo- gical processes and the appropriate use of relationships between key soil characteristics and management options. It is argued that local knowledge is not suf®cient to cope with uncertainty introduced by a rapidly changing agriculture, including, for example, increasing land pressure, unpredictable market forces and cli- mate change. We have suggested how scienti®c knowledge can contribute to the solution, based on an analy- sis that relates Cohen's (Heuristic reasoning about uncertainty: an arti®cial intelligence approach. Pitman London, 1985) and Rowe's (Risk Analysis 14, 743±750, 1994) uncertainty concepts to local knowledge. Keywords: Agricultural risk management, local knowledge, nutrient budgets, soil fertility management, uncertainty, Andean hillsides INTRODUCTION Background and objectives Hillside agro-ecosystems in Colombia have a complex physical structure. Intense rainfall and resulting soil erosion often introduce extremely large spatial and temporal variation in soil resources that is further accentuated by fertilizer application. There is considerable evidence that farmers identify and use variation at scales relevant for management (Carter & Murwira 1995; Barrios 1996; Murage et al. 2000). Farmers have learnt how to manage their soils aided by local knowledge and experience. Their approach to soil management is dynamic in the sense that they employ their knowledge of relationships between management and environmental response to sustain pro- ductive capacity. Encouraging as this is, increasing land degradation suggests that locally devised methods, on their own, are no longer effective enough to cope with rapidly changing pressures on farmers (Johannes & Lewis 1993; Murdoch & Clark 1994). Farmers generally possess a large body of knowledge about physical resources on their farms but this knowledge is mainly based on what can be seen on their land (Talawar & Rhoades 1998) rather than on generalized knowledge. Although farmers are aware of the ecological changes induced by their land management, their understanding of the underlying causes is probably incomplete and prevents better soil stewardship. This pushes the managment of an agricultural system beyond empirical evidence. As Polunin (1984) described it, external events interfere with the traditional management. The lack of speci®c knowledge concerning environmental processes such as nutrient leaching and nutrient ®xation in cropping systems creates uncertainty that obstructs sound decision- making when changes have to be made. This uncertainty prevents farmers from taking decisions that are too risky and may have contributed to their reputation of being risk- averse. Uncertainty is removed by information that explains the resources and their management and how they may respond to change. Information about sustainable land-use options is available to parts of the local farming community. However, adoption of these options has been slow. In fact, the 1 Land Use Project, 2 Tropical Soil Biology and Fertility Institute of CIAT, Centro Internacional de Agricultura Tropical (CIAT), A.A. 6713, Cali, Colombia. * Corresponding Author: Fax: +57 2 445 0073. E-mail: t.oberthur@cgiar.org T. Oberthu Èr et al. 23