Soil erosion is recognised as being the major problem in cultivated sloping uplands in Southeast Asia (Cruz et al.1988; Garrity 1993; Fujisaka et al. 1994; Garrity et al. 1995). It is one of the major problems besetting the uplands of the Philippines and causes rapid degradation in soil quality, nutrient depletion and decline in crop productivity (Lal 1984; Stocking and Peake 1986; EI-Swaify 1993; Turkelboom et al. 1993). Contour hedgerow systems using nitrogen-fixing trees have been promoted to miniraise soil erosion, restore soil fertility, and subsequently improve crop productivity (Huxley 1986; Young 1986, 1987; Kang and Wilson 1987), and have been a common feature of extension programs for sustainable agriculture on the sloping uplands in Southeast Asia (Garrity 1996). This innovation has not been widely adopted by the upland farmers (Fujisaka et al. 1994), despite positive results having been observed and reported in a number of experimental and demonstration sites. Constraints that limit the effectiveness and adoption of pruned-tree hedgerows include the tendency for the perennials to compete for growth resources, and hence reduce yields, of associated crops planted in adjacent rows, and the inadequate amount of phosphorus recycled to the crop in the prunings (Garrity 1996). But the major problem is the enormous amount of labour needed to prune and maintain them. In one study, farmers' labour investment to prune their leguminous-tree hedgerows was about 31 days per hectare, or 124 days annual labour for four prunings (ICRAF 1996). There is a need for a simple, less labour intensive by effective contour hedgerow system.
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