s:2411:"TI Building research on farmers' innovations: low-cost natural vegetative strips and soil fertility management 
AU Stark M 
AU Garrity, D.P. 
AU Jutzi S C 
AU Mercado Jr A R 
AB Contour hedgerows using nitrogen-fixing trees have been widely promoted in Southeast Asia to minimize soil erosion and improve crop yield, but few farmers have taken them up. This is partly because establishing and managing such hedgerows is very labor-intensive. The spontaneous use and rapid dissemination of narrow buffer strips consisting of natural vegetation, so-called Natural Vegetative Strips (NVS), among farmers in the Philippine uplands has provided a low-cost, yet effective alternative to the establishment of tree hedgerows. Formal research on this farmer technology proved that NVS are at least as effective in controlling soil erosion as tree hedgerows, while causing minimal competition effects on the associated field crop and requiring only a fraction of the labor needed to establish and maintain pruned tree hedgerows. As in conventional hedgerow systems, however, natural terrace formation resulting from the redistribution of sediment from upper to lower terrace zones, a process called ‘scouring’, leads to the development of a soil fertility gradient. The result is a significantly lower crop yield on the degraded upper terrace. The assessment of farmers’ strategies to improve crop yield on the upper terrace concluded that practices, which increase soil organic matter levels and raise the soil pH, may be needed to sustain yield in NVS systems in the long run. Future collaborative research by the International Centre for Research in Agroforestry (ICRAF), national agricultural research institutions and farmers will focus on validating and adapting the NVS technology under the contrasting conditions of the shallow, marine limestone-derived soils typical of the central Philippines. This is another major soil environment in Southeast Asia. The evolution of NVS systems to more complex agroforestry systems through the planting of fruit and timber trees along the contour strips will be further assessed. Facilitating and strengthening the collaborative efforts of farmers, local governments and technical providers (researchers, technicians) will be more widely tested as a successful model for the efficient development and dissemination of appropriate soil conservation technologies. 
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