Indigenous knowledge and classification of soils in the Andes of Southern Peru

Indigenous cultures throughout the world have substantial, systematic knowledge of soils gained during many generations of land use; however, little of this knowledge has been scientifically documented. Recent literature indicates that knowledge among traditional cultures could add to scientific understanding of soils and be useful in international agricultural development. This study investigated indigenous soil know ledge in the Colca Valley, Peru, where terrace agriculture has been practiced for at least 15 centuries. Previous research suggested enhanced tilth and fertility of ancient agricultural soils, measured by criteria such as thickened A horizons, lower bulk density, and greater levels of organic C, N, and P relative to nearby uncultivated Mollisols. Long-term soil conservation is partly attributed to traditional management practices such as terracing, a form of conservation tillage, fertilization, and irrigation. To test the hypothesis that a body of knowledge underlies traditional soil management practices, interdisciplinary studies were conducted, involving linguistic evaluation of soil terms, anthropological field interviews, soil and geomorphic mapping, and basic morphological and laboratory characterization of soils identified by farmers. Anthropological research revealed a hierarchical soil classification system, with up to four categorical levels and about 50 soil and earth material names, that emphasizes soil texture and other properties important in agricultural management. Soil analyses indicated a fairly close correspondence between indigenous texture classes and those used in U.S. soil classification. Local farmers recognize several soil features and horizons such as duripans, soil variation with depth, distribution of soils on the landscape, and changes in soil behavior under different conditions.