Alternatives to traditional annual crop agriculture in the uplands : biophysical evidence from the Manupali River watershed

"Maize and commercial vegetable production are important features of the agricultural landscape in the Manupali River watershed. These crops, as currently produced, are associated with a number of environmental concerns in the watershed, including high rates of soil erosion (see Chapters 7 and 8, this volume) and - in the case of vegetables - high rates of pesticide use. Soil erosion and associated declines in land productivity and farm income in steep-land crop production systems have been shown to be major threats to agricultural sustainability in the Philippines (Presbitero et al., 1995; Poudel et al., 1999, 2000) and elsewhere (Alegre and Rao, 1996; Gachene et al., 1997; Roose and Ndayizigiye, 1997; Sen et al., 1997). In addition to the on-site effects arising from soil erosion, a number of off-site effects have received attention as detailed elsewhere in this book. The sedimentation of dams, reservoirs, irrigation canals, and degradation of the quality of coastal habitats and tourist locations reflect some of the downstream negative impacts of soil erosion that have major ecological, economic and environmental consequences (Heusch, 1993; Ciesiolka et aI., 1995)." -- pp. 133-134.