Managing soil fertility on terraces forming behind vegetative filter strips: an assessment of farmers' strategies

The indigenous use of natural vegetative strips (NVS) to control soil erosion on the slope has been viewed as a low-cost alternative to planted tree hedgerows. As in conventional hedgerow systems, however, natural terrace formation resulting from redistribution of sediment from upper to lower terrace zones leads to the development of a soil fertility gradient with significantly lower crop yield on the degraded upper portion of each terrace. Since NVS produce little biomass which could be used to maintain soil fertility, the sustainability of annual crop production in NVS systems may be questionable Interview surveys conducted in two upland locations in the Philippines showed that most farmers had observed soil fertility scouring to adversely affect crop performance on the upper part of the terrace. However, scouring was not usually perceived as a serious constraint of the technology. Farmers claimed that the benefits of overall increased crop yield and rise in land value due to contouring outweighed the negative effects of upper terrace yield decline; besides, they generally believed scouring to be a transitory phenomenon. On-farm experiments were conducted to assess farmers’ strategies to overcome the negative effects of soil fertility scouring in NVS systems by skewing the application of nutrient inputs towards degraded upper terrace zones. Further research is required to identify methods to fully rehabilitate the degraded upper terrace through raising soil organic matter levels

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